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Reinstalling quadrajet and as much Emissions as possible
Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Re: Reinstalling quadrajet and as much Emissions as possible
You are right CindyL, and it is confusing.
Here is what I can tell you:
Top - H - control vacuum.
2nd down - PCV - goes to K. L can be used also.
3rd down - carb bowl - goes to T.
Bottom - Can/TVS - to canister.
I have an 84 T/A and will be going to a MANUAL Quadrajet with no ECM and vacuum advance distributor.
I hope this doesn't confuse you, but here is the diagram I came up with for mine and it does match the way that your CCV is labelled.
Last edited by NoEmissions84TA; 01-08-2022 at 07:33 PM.
Re: Reinstalling quadrajet and as much Emissions as possible
sofakingdom, sorry, I think my confusion led to a confusing post. I do know letters are stamped on the carburetor. What confused me was that the third from bottom port (or second from top) on the CCV says "PCV", but according to the hose routing diagram it doesn't come from or go to the PCV. Instead, according to routing diagram it goes from that port on the CCV to the K port on carb, with a hose from the canister purge valve teeing into the line btw the CCV and the carb. Just wanted to make sure I was reading the diagram correctly. Or I suppose I could have the wrong CCV.
But, while on the subject, I have been curious as to why those letters. That is why "J" for EGR-you would think it would be an "E". Why "N" for the vac sensor?.....
While I am it, also on the carb there is this grid pattern, with the letters A through N, on the left, To the right of each letter are three grid boxes with punch marks. Some letters have one punch marks, some have two, some have none. What is this. Are the punch marks denoting the number of ports marked with each of the letters..
Re: Reinstalling quadrajet and as much Emissions as possible
No idea why the letters don't "stand for" their function, beyond that, if they did, and another function were to be introduced with the same initial, that the system would instantly become broken.
AFAIK the markings in those grid areas are for things like the particular mold cavity that was used, the shift during which it was cast, etc. Bookkeeping type things. Nothing particularly related to functionality.
Be aware also, NoE's diagram up there is for M4ME, not E4ME. You have the E (Electronic) version of the 4M (QuadraJet) with E (electric) choke, not the M ("Modified"... 70s emissions version) of model 4M w electric choke. That diagram isn't the same as for your car.
For yours, H is the ported vac source (about 3/16" hose, down low on the front, right in front of the center of the driver's side bore next to the TPS connector); pretty sure K is the carb bowl vent, is a 3/8" (big) fitting, and has no check valve; can't remember what T is but I think it's a small fitting in the throttle plate on the driver's side; L is the 3/8" fitting for the PCV in the throttle plate.
Here's my carb and vac diag. Yours is virtually identical except for the dual snorkel air cleaner. B is at the top pass side of the fuel bowl and has that little curved line in this pic: don't ask me why the factory left the vac diaphragm for choke pulloff and secondary opening timing off of their diagram, just goes to show that even their own diagrams aren't always 100% dependable. J is down near the bottom straight below it. K is front and center top of the carb, right above the fuel filter.
Last edited by sofakingdom; 01-10-2022 at 12:56 PM.
Re: Reinstalling quadrajet and as much Emissions as possible
Thanks guys. Makes more sense now knowing there may be other applications that use PCV and canister together, and have always just wondered about the letters and grid thing.
On the ECM--I have a couple of questions. I have read several posts on here with people trying to diagnose problems. A lot of times they will replace several switches or valves, etc., only to later find out is was a blown ECM fuse or blown ECM. I recently pulled some some codes from mine (13 and 23). The question is, given that it put out codes, does that mean the ECM is working fine, and there is no need to question its functionality, or even whether it has a blown fuse.
Also, the Haynes Manual (as well as numerous posts on here) describe how to pull codes (the paperclip thing). Haynes says to put the key in ON position---not the Start position. Also says you can do carbureted models with engine running. So, when I pulled codes, I was unsure of where to put the key. Seems like once you turn key there is sort of like a free play area, and then a stop, and if you push past that stop, it cranks. So when I did it I tried pulling codes in that free play area, not on that first stop. Nothing happened. I didn't want to mess anything up so ended up pulling codes with car running. Can you tell me, if I want to pull codes with engine not running, do I go to that first stop (pretty sure I just wrote another confusing post). Do you know what I mean??
Re: Reinstalling quadrajet and as much Emissions as possible
Originally Posted by CindyL
Thanks guys. Makes more sense now knowing there may be other applications that use PCV and canister together, and have always just wondered about the letters and grid thing.
On the ECM--I have a couple of questions. I have read several posts on here with people trying to diagnose problems. A lot of times they will replace several switches or valves, etc., only to later find out is was a blown ECM fuse or blown ECM. I recently pulled some some codes from mine (13 and 23). The question is, given that it put out codes, does that mean the ECM is working fine, and there is no need to question its functionality, or even whether it has a blown fuse.
Also, the Haynes Manual (as well as numerous posts on here) describe how to pull codes (the paperclip thing). Haynes says to put the key in ON position---not the Start position. Also says you can do carbureted models with engine running. So, when I pulled codes, I was unsure of where to put the key. Seems like once you turn key there is sort of like a free play area, and then a stop, and if you push past that stop, it cranks. So when I did it I tried pulling codes in that free play area, not on that first stop. Nothing happened. I didn't want to mess anything up so ended up pulling codes with car running. Can you tell me, if I want to pull codes with engine not running, do I go to that first stop (pretty sure I just wrote another confusing post). Do you know what I mean??
I always read the codes with the key in the on (run) position, but with the engine not started. When I say the on position I mean turn the key just until the power comes on for the radio, wipers, heat/AC, the dash warning lights, all the stuff controlled by the key, but don't turn it far enough to crank the starter. As to fuses, if your ECM is returning codes, the fuses are OK , but this of course is not proof of a 100% functional ECM (a good running engine is the best proof of an ECM's condition)......
Re: Reinstalling quadrajet and as much Emissions as possible
Thought I would take a few days to regroup. See what I have, see what I don't have, and whether I have any more questions.. Thought I would also see if I can wrap my brain around learning how to use a voltmeter. Sort of doubt, but I can at least try. The carb is still out being rebuilt--the guy is taking forever, so moving forward is on hold till at least then. If anyone has any thoughts on something I haven't mentioned, but would be important and useful info for the swap (back to original carb and intake manifold) or reinstalling or testing any emission components (remember I have no AIR system or EFE left) please let me know. I'll check back in next week. Thanks for all the help so far.
Re: Reinstalling quadrajet and as much Emissions as possible
Originally Posted by T.L.
Did you get that TVS I showed you? I later realized that it is the one used for the '82-'84 models, and for some strange reason, they changed the vacuum hose configuration for the CCV in '85, which uses a smaller vacuum hose and therefore a TVS with smaller ports. I hope I didn't screw you up by recommending that TVS. I just knew it is what my car uses. Of course you can use the vacuum diagram that NoEmissions84TA posted (and it will work), but it won't match the diagram on your core support.
Re: Reinstalling quadrajet and as much Emissions as possible
T.L. not a problem. Just to confirm, the oem for the TVS is 3031385-right?? So, if I can find one of those (have looked and looked and can't find one) or an equivalent from a different manufacturer, that would be the right part?? I did find a Carter PV-13, which I think is the Carter equivalent for the 3031385-right?? Anyway, thanks for the correction. Oh, I did learn yesterday that what I have is a multimeter--but couldn't even figure out how to test a AA battery. Lots more reading and learning to do!! This thing makes me nervous -SHOCK!!
Re: Reinstalling quadrajet and as much Emissions as possible
If you use the nylon tubing and the rubber ends that you can get on cards in the parts stores, you can pick and choose the diameters at the fittings and make up whatever line you need. (within certain limits...) Unlike rubber hose which is the same at both ends as well as all the way down the middle.
Re: Reinstalling quadrajet and as much Emissions as possible
naf, Below is a pic of the bracket I mentioned, and a second pic of what looks to be a second bracket that looks like it was cut off. The first bracket I thought might be a resting place for the snorkel or intake tube, then thought maybe it was for the stove pipe, and now have decided I don't know what it is. It is drivers side, bolted to the bottom of the valve cover (or rocker arm cover--is there a difference?). The second pic is what looks to be the remains of some hardware store-ish bracket bolted to the other end of the valve cover, and which appears to have been cut off. Can you tell me what they are for??
Re: Reinstalling quadrajet and as much Emissions as possible
CindyL, are there any car shows near you (I know, not this time of year) that might have a stock 3rd gen of a similar year as yours? Go there with your camera and ask the owner if you can take pictures. Remember, a picture is worth 1000 words.
There must be youtube videos on how to use a multimeter.
Here is one:
Re: Reinstalling quadrajet and as much Emissions as possible
The bracket in the first pic looks familiar, but I don't remember what it does or holds.
That little tab in the second pic looks like something added to hold those spark plug wires.
Re: Reinstalling quadrajet and as much Emissions as possible
That bracket in the 1st picture is correct to this engine. It bolts down to the foward valve cover bolt. It's purpose is to allow that "cluster" of wires that are around it to be routed on top and lay in the channel to protect them from the exhaust manifold.
Re: Reinstalling quadrajet and as much Emissions as possible
Originally Posted by joeld
That bracket in the 1st picture is correct to this engine. It bolts down to the foward valve cover bolt. It's purpose is to allow that "cluster" of wires that are around it to be routed on top and lay in the channel to protect them from the exhaust manifold.
Re: Reinstalling quadrajet and as much Emissions as possible
right, the temp sensor wire and the wire to the O2 sensor go through the little clamps on the bracket in the first pic.
the second bracket doesn't look to be factory, it may have been someone's attempt to hold the spark plugs up away from the headers. the factory routing was underneath, below the factory exhaust manifold.
do your headers have an O2 sensor bung? maybe in the y-pipe?
Re: Reinstalling quadrajet and as much Emissions as possible
So, none of my guesses were right. Joel was right. Yesterday I started looking through this parts catalogue I had downloaded a while back. JACKPOT!!! OEM numbers for every part, plus PARTS DIAGRAMS!!! Woohoo!! The description for that part was "Bracket, park plug wire". Same thing for the other cut off bracket (that one obviously not original to car). Watched the you tube video, and think I'll have to find one for the multimeter that I have, but learned a little. Thanks. Car show-good idea, and Sofakingdom, (nooby question) I thought there were a multitude of rubber connections for rubber hoses, where you change the diameter to make the connection (such as the MAP connector from the hose nipple on it to the little black hard vacuum line?? Can you explain? Yes, I do have an oxygen sensor bung, not sure whether the bracket to hold the wire up is there-keep meaning to check that.
Re: Reinstalling quadrajet and as much Emissions as possible
Well, I spent the last week re-grouping on my parts search, wiping down my engine bay, trying to clean up the original intake manifold (to be installed with original carb), watching videos on how to use a multimeter, and beginning to look at how to use my new vacuum gauge. Thinking it might be a good idea to try and start testing some components. I have read numerous posts on how to clean up the manifold. It has already had a chemical bath but still remains mostly back on top. Am now trying Simply green. Any suggestions would be welcome. Have learned a little about the multimeter, but the learning curve is slow. Will keep at that.
Anyhow, just a couple of quick questions.
Can anyone explain/describe, or maybe take a pic of how that wire support bracket is to be oriented. I know it bolts to front bolt on rocker cover, but mine has been bent all out of shape, and I'm not sure what it's correct shape is supposed to be, and where it should be pointing. Right now, as you can see in the pic above, it's pointing to the brake master cylinder, but there is no way the spark plug wires could reach out towards the master cylinder and then reach back to cylinder head or distributor.
Also, I have read several posts that talk about a heat shield between the carb and intake manifold. In addition, the parts manual notes a "heat insulator" there. I thought it was just a gasket. So the question is, is a heat shield necessary, or is a gasket all you need.
On the intake manifold bolts--sofakingdom mentioned that the original intake manifold were flanged (and I guess had no washers). Has anyone noticed any benefits from using regular bolts with washers, or bolts with flanged heads. I ask because I have had my intake manifold gaskets replaced twice now, and am still getting puddles of oil in the little wells surrounding some of the bolts. Have read a number of posts suggesting it may be because of a lack of sealant on the threads of the bolts when they were reinstalled. We will certainly make sure that we do that, but thought maybe there may be some advantage to using flanged bolts, or unflanged bolts, that I am unaware of.
Last, is it worth the money to get a scanner. I have read they are of minimal help with obd1 cars. Any thoughts would be appreciated.
Re: Reinstalling quadrajet and as much Emissions as possible
Any suggestions would be welcome.
Take it to the quarter car wash, along with a can of Permatex 4MA. Can of satin black engine paint afterwards.
heat shield between the carb and intake manifold
There isn't one. Not sure what people might be posting about such a thing.
is a gasket all you need
Yes. It's VERY thick, like 3/8" or so; I suppose it could be considered a heat insulator as well as a gasket.
Has anyone noticed any benefits from using ... bolts with flanged heads
Yes. They spread the load out on the surface, and don't dig into the soft aluminum like regular bolts will.
a lack of sealant on the threads of the bolts when they were reinstalled
That will result in puddles of oil every time. You can take them out one at a time and put some sealer on them. The 4 center ones on each side need this, as described earlier. Use the Permatex/Loctite "hi-temp automotive thread sealer with PTFE", found in a small tube on a card in the gasket section of your corner parts store. Torque them back down to about 25 - 30 ft-lbs (a good solid pull on a 9/16"-5/8" double box-end wrench). No need to either gorilla them or get all wound up in their exact torque. You will likely find however, that after you do this, the other 4 on each side will be loose; go ahead and tighten them all evenly about the same, at which point the center 4 will be loose again; continue to re-tighten evenly until all 6 on each side are at 25 - 30 ft-lbs.
is it worth the money to get a scanner
Not really. The data rate coming out of the port is about 100 baud, AT BEST. It's too slow to be of any real value for things like data logging except in the grossest and most brutally time-averaged way. Not anything like "tuning" or "logging" a 21st century car. To get any "codes" from the ECM in the carbed cars, you can buy a whole box of totally adequate scanners for about $5. https://www.staples.com/Staples-1-Si...product_472480 Remember that brick phone you were using to Facebook on back in about 1976? That was WAY AHEAD OF the level of technology of the ECM you have.
Re: Reinstalling quadrajet and as much Emissions as possible
Originally Posted by CindyL
Also, I have read several posts that talk about a heat shield between the carb and intake manifold. In addition, the parts manual notes a "heat insulator" there. I thought it was just a gasket. So the question is, is a heat shield necessary, or is a gasket all you need.
Re: Reinstalling quadrajet and as much Emissions as possible
CindyL I messaged you again this morning, I will be at the shop today and can video the whole engine for you, I pulled it complete on the k-frame so everything is on it. I have a LOT of what you need or looking for.
Re: Reinstalling quadrajet and as much Emissions as possible
Thanks again for the responses. Been sort of slow going. Hard to spend anytime in the garage bc of the northeast weather. Learning how to use the volt meter is an ongoing process. Thought I learned a little then looked at the instructions in the FSM on how to test the MAP, and realized I didn't have a clue. Anyhow, I think I am fresh out of questions for now. We should be able to pick up the rebuilt carb this week, and I have a number of additional parts to get. Then I am thinking I might wait until mid March to have the work done. It is just too darn cold--things tend to break or snap off more easily.--like my hanging door handle. I will let you know if I have any more questions, and will keep you posted once we start the repairs. Hopefully all goes well, but I know getting some troubleshooting advice from third gen'ers would be very helpful. Thanks again for all the help so far.
Re: Reinstalling quadrajet and as much Emissions as possible
I knew once I said I had no more questions-one would pop up. Is there a way to test the vapor canister valve--the flying saucer looking thing, about 6-8 inches away from the canister. Think I might have gotten a dud.
Re: Reinstalling quadrajet and as much Emissions as possible
Originally Posted by CindyL
I knew once I said I had no more questions-one would pop up. Is there a way to test the vapor canister valve--the flying saucer looking thing, about 6-8 inches away from the canister. Think I might have gotten a dud.
Not sure, but isn’t that the cruise control if equipped. Also there is a vacuum storage can down below the inner fender ( on driver side) and above the fender skirt, at least my 86 Iroc has that.
Re: Reinstalling quadrajet and as much Emissions as possible
If you have the original hood on the car with the emissions sticker, you will see the routing of all the vacuum lines for the EGR, AIR, EVAP and EVE and you will see the two TVS vacuum switches. You have to be careful because GM strategically placed some vacuum "TEE" fittings to supply vacuum to various circuits so if your plan is to take everything apart to repair/replace, you must follow the schematic on this decal perfectly. And, if you are deleting any features, you must cap off any unused connections on the carb or in the lines to avoid vacuum leaks. These leaks could effect performance and make the features you want to keep not work properly.
Re: Reinstalling quadrajet and as much Emissions as possible
Just thought I would give you all a quick update. Took the car to a mechanic to have the original intake manifold and carburetor (rebuilt) reinstalled on my car, along with numerous other related parts. The related parts include reinstalling a new negative backpressure EGR, new oxygen sensor, new knock sensor, new spark plugs, new TVS in intake manifold, new mixture control solenoid connector, new throttle position sensor connector, new distributor cap, cover and rotor, new TV cable (sold as and stamp marked with oem number). Also got an oem air cleaner and breather tube from a couple of very nice third genners (also got a number of other parts from one of the gentlemen, who was taking apart a 1986 Camaro IROC, and those parts were invaluable, like the original hose connector to the EGR Solenoid, and the check valve from the CCV to carb, the spacer for the EGR--great stuff!).. Also got nos valve covers so they look as nice as my rebuilt carb and repainted air cleaner. Gave him all the hoses to and from carb and CCV, all marked as to where they go, along with al new gaskets for carb, distributor, EGR valve, Water Neck. As you may recall, this is all in an effort to get the car to pass emissions (and to be honest I wanted to go back to original setup anyhow). As an aside he will also be looking at the brakes, bc the mechanic before this one tried to do a quick fix on the right rear brake bc he said it was dripping oil/grease on the drum/shoe causing it to fail the dmv brake portion of inspection; however that fix caused the car to vibrate a bit at about 40 mph, and very bad vibration and pulling hard to the right when braking. I have great hope all of this work and I can finally get the car back on the road. It has now been with the mechanic for three weeks. Fingers crossed!! I wanted to again thank you all for all of your help. I learned so much.
Re: Reinstalling quadrajet and as much Emissions as possible
I'm back. The mechanic has finally started working on the car, and I have a couple of questions. He says he put the Q-jet back on, and he thinks the carb gasket is binding up the throttle linkage. More specifically he said he thinks the carb gasket is binding up the throttle plates. Also said he had run into this before. Anybody ever have that happen?? Attached is a pic of the gasket I gave him.
Also, he is wondering what the EGR Solenoid is supposed to attach to, he says its just hanging there. I told him I thought it had been connected to something when we dropped the car off--just can't remember what? Just as a reminder this is a 1986 Firebird, 8cyl, 305, carb'ed LG4 engine.
Sorry about the picture size--can someone enlighten me as to how to make them smaller, but not tiny. As always thanks for any and all help.
Re: Reinstalling quadrajet and as much Emissions as possible
Thanks for the response naf. Just read a little bit about the throttle shaft--just to figure out what you were referring to. You learn something new everyday!. So, we did have the carb rebuilt. Can you tell me whether normally, the throttle shaft is replaced or cleaned, or new bushings put in when a carb is rebuilt. Also the mechanic mentioned the choke thermostat. Again, the question is---is a new thermostat normally put on in a carb rebuild. Just trying to figure out whether we can likely rule out any problems with the throttle shaft, and the thermostat. I suppose we could call the carb guy who rebuilt it, but it has been months since he rebuilt it, and probably won't remember one way or another. Thanks again for the help naf.
Re: Reinstalling quadrajet and as much Emissions as possible
Pics show an Edelbrock Performer EPS intake manifold.
She previously had an Edelbrock 1406 carb on it.
Does that manifold have the flange to work with a spread-bore carb like the Q-Jet?
I think she now has a spread-bore carb on a square-flange manifold. That ain't gonna work.
CindyL, what is the number on your intake manifold?
Last edited by NoEmissions84TA; 08-25-2022 at 09:08 PM.
Re: Reinstalling quadrajet and as much Emissions as possible
The carb on the car is/was an edelbrock 1406 and the intake manifold is/was an edelbrock 2701. I say is/was bc we are (or the mechanic is) in the process of hopefully reinstalling the original GM intake manifold and the original quadrajet. Things are not going as smooth as we had hoped. The mechanic said one of the manifold bolts was stripped, the electric choke may need to be replaced, and as stated above, thinks the carb gasket is causing the throttle plate to hang up, among other things (have read naf's thought on the throttle shaft bushing, and am thinking if that's the problem maybe Cliffs High Performance throttle shaft bushing rebuild kit may be the answer). Anyhow, the whole spread bore/square bore thing is not an issue, unless we are unable to use the original intake manifold, or the original carb for some reason. Thanks for the thought though.
Re: Reinstalling quadrajet and as much Emissions as possible
easy enough to check the throttle bore for play. take the spring off and see if it will move with it held open slightly. -if it's closed the blade will be tight in the bore and you won't feel it move.
usually only the driver's side primary bushing needs to be replaced.
a rebuild won't necessarily come with a new choke thermostat.
Re: Reinstalling quadrajet and as much Emissions as possible
Another quick question: The mechanic can't find the oxygen sensor wire. My oxygen sensor is located on the drivers side. It heads up to just above the valve cover and then towards the front of the engine (front of carb). He can't find the end that comes from the ecm. Does anyone know if its in one of the large wire looms and which one?
Re: Reinstalling quadrajet and as much Emissions as possible
Thanks naf, always helpful. He says he figured it out--saying he got confused bc he believes the sensor was originally on passenger side, but got moved to drivers side when PO installed the aftermarket headers. Anyhow, while I have your ear (if I still do) you had mentioned play in the throttle bore---I have purchased a used quadrajet to rebuild (same carb #as the one on my car) to try and help me understand the various components and how it works (in midst of reading Ruggles book and then will read the FSM on the E4ME). When you say play in the bore--can you tell me if any degree of play warrants the bushing replacement. That is, on this used qjet,it moves maybe a 1/32 of an inch back and forth, not so much up and down. Honestly, am thinking I'll try the bushing replacement, just for the learning experience, but would that little play warrant the bushing replacement. Thanks again.
Re: Reinstalling quadrajet and as much Emissions as possible
At ~ 0.030" of play in the throttle shaft, that allows more than enough movement to bind throttle plates and/or prevent reliable and repeatable closure of the throttles. That would have a significant effect on tuning at idle and low RPM, and the TPS and mixture control could struggle with that.
If you only do the primary shaft it will usually solve most (if not all) of the problems. Moreover, unless something really unusual has occurred, only the outboard bore on the linkage/belcrank side would need to be replaced.
Re: Reinstalling quadrajet and as much Emissions as possible
I'm back again---with no good news. Stopped by the mechanic today, and although he has the car back together it is running rough. Just to refresh your memories--we had the original qjet and intake manifold put back on the car, along with new plugs, wires, cap, rotor, oxygen sensor, egr valve, pcv valve, and more, in an effort to finally get the car to pass emissions. The car starts but runs rough. The mechanic believes there is a significant air leak in our carburetor. Once the car warms up, it will not idle. It just sputters and dies. He says that when he blocks the carburetor air intake (puts his hand over the top of the carb) (before it sputters and dies), the engine revs about 1000 rpm (idle increases). He says that is evidence of an internal carburetor air leak. As a last resort, he plans to adjust the mixture control valve and says that there is a chance that is the problem rather than an air leak. But if that doesn’t work, he thinks we may need to replace the carburetor.
We had the carburetor professionally rebuilt before we gave it to our mechanic to install. So we think the carb rebuilder would have told us if there was an internal air leak that would compromise the operability of the carburetor. Also, among other things, the carb rebuilder replaced the bushings on the throttle linkage, so that should not be the source of an air leak.
We would appreciate any thoughts or insight into what might be happening here. Thanks as always.
Re: Reinstalling quadrajet and as much Emissions as possible
I know, I know. The above post was bad. First wondered whether I should just start a new post in the carb forum, or on this one--given its all related to the whole carb and intake reinstall and emissions system. Second, how are you all supposed to help without any specifics, like was the car cold or warm, what exactly was it doing, are there any error codes. Sorry, I had just gotten back from the mechanics and was a bit spooked. He's had the car for four and a half months, and it sounded so bad. Really wish we had just done the work ourselves, but we have little to no experience (but have been reading and learning a lot in the past year, on this forum and with the FSM and Ruggins book on qjets). As for the specifics, I really didn't have any. Don't know if it was cold or warm, any error codes, etc.
Anyhow, let me ask something a bit more specific. The mechanic kept saying it idled really rough once warmed up a bit. He started the car, it idled very roughly, and then he starting moving the choke flap a lot to keep it running. He said he thought there was a big air leak in the carb and it may be internally cracked. He would then put his hand about an inch above the carb (restricting air flow) and the idle increased. He said that indicated an air leak. So here's the question. Could a bad oxygen sensor, or an oxygen sensor that is there but is not wired correctly cause these symptoms. I ask that because we had a very confusing conversation about the oxygen sensor. He said he couldn't find the end of the oxygen sensor wire; however we labelled it and zip tied it just above the valve cover when we gave him the car and remember it then went in front of the carb and then into a wire pack.. Also, later he said he figured it out, saying he realized the sensor was originally on the passenger side: however, as T.L. said, it was always on the driver side. So, again if he somehow wired the oxygen sensor wrong, could it cause a very rough idle, especially when car is warmed up. I think I know the answer (yes) but before suggesting it to the mechanic (who's been doing this for 35 years or more) I thought I would get the firebird gurus thoughts. Also, would adjusting the mixture control valve, as he is planning to do, speak to these issues. On a final note, am thinking about just having the car towed home, and trying to finish the job ourselves (my husband and I)--but that's a bit scary to me.
Re: Reinstalling quadrajet and as much Emissions as possible
Originally Posted by Vader
If headers are something you want to retain, this might be an option:
Are they "Dyno Don" headers ? Whatever they are, how do they fit? Must anything be bent, removed, or otherwise "compromised" for the headers to fit? I'm asking regarding my '89 IROC VERT and a likely L98 or L31 Swap? PM me or brief reply, here, if you anyone wishes. thanks.
Re: Reinstalling quadrajet and as much Emissions as possible
I wouldn't have much faith in the mechanic and it's only costing you money for something you probably can't screw up and worse than they have. Sounds like it's very lean, possible large vacuum leak
Re: Reinstalling quadrajet and as much Emissions as possible
Thanks for the responses. Helpful in that I keep thinking that. Funny thing is while we are standing there and he's messing with the choke flap to keep it running, we notice that Carb port B (the one that goes to the air cleaner) is open and not capped. So we ask.........did you try capping the open ports and get it to idle right and he says Oh yeah. Is that not a vacuum leak?????? or do I need to do a lot more reading. I am serious. While my itty bitty education on this stuff, leads me to think this is a vacuum leak, I wouldn't put a hundred dollars on it.
Re: Reinstalling quadrajet and as much Emissions as possible
O2 sensor won't cause the issues you're seeing.
a vacuum leak will cause it to idle high, enough of a leak will not allow it to drop down to lower curb idle speed.
of course there's a lot of adjustments and settings that we don't know are correct or not, so it's difficult to diagnose.
if all of the carb settings are close to correct, AND assuming the ignition system is functioning and timed correctly, it should be able to idle enough to fine tune the Idle Air Mixture screw (the one on top). the idle mixture screws (low front) would be one of the 'carb settings' that would have to be close to correct.
I'm not going to disparage the capabilities of your current mechanic but if you want to take it home, we'll work with you best we can to try to get it running better.
that said, many of these parts are, at best, near 40? years old. a bad qjet core is a possibility. maybe you could ship me yours and I could try to run it on mine, or I could ship a loaner to you to try on yours.
01-08-2022, 07:15 PM
Look closely. 
