ATX-Iroc

Ive got an 87 305 tpi and it just started surging really bad at idle. I think I may have found the reason for it but want yalls opinion before i drop coin on a new throttle body. I did my version of a smoke test by blowing cigar smoke into the brakebooster hose and saw smoke come out on both side of the tb shaft. Would this really make my car run that bad, its kind of like break the tires loose then almost die and do it over again. It goes away when I unplug the esc connector though. Can I make an lt1 tb work tpi?

ATX-Iroc

The best way to summarize this is that the car runs better with esc wire disconnected. When I connect it timing goes up to 55 degrees. Anyone got any ideas

83 Crossfire TA

iTrader: (2)

1- blowing into the hose- doesn't make sense, you should have vacuum at both points so I don't see anything coming out at that point no matter how badly your throttle shaft is worn

2- 55* @ IDLE??? yea, your timing is messed up, what does it read with the tan/black stripe wire disconnected (I'm assuming that's where you're disconnecting the esc)?

ATX-Iroc

The reason I blew into the hose was to fill the plenum with smoke and the smoke seeped out from both sides of the tb shaft. As far as the timing goes it just went back to normal after I took everything apart and checked everything with a volt meter. I'm when I was getting at the ignition parts I tapped an injector and it hissed at me so I'm going to try some new injector o-rings. Seems odd that it would hiss, if I have this giant vacuum leak shouldn't the plenum shouldn't not have vacuum after the engine is turned off

ASE doc

The most common cause of surging idle is a lean condition. Connect a scanner, since you have a smoke machine i assume you have a scanner, watch O2 voltage, integrator, and block learn. Look for high BL and integrator numbers. Hows fuel pressure, MAF voltage, TPS. I suspect your MAF is dirty or failing. Try unplugging it and starting the engine without it. This forces the ECM into memcal and ignores the MAF. Do integrator and block learn numbers level out? If so, clean or replace the MAF as needed. If BL and integrator numbers look normal on your initial scan, the problem could just be your IAC valve. Try unplugging it with the engine running, see if the idle levels out. If so clean or replace the IAC, check the passages.

ATX-Iroc

Wait I'm supposed to watch the engine suck the smoke in right

ATX-Iroc

I don't have a scanner or smoke machine just a big fat cigar. I cleaned the iac just yesterday and no change. There has to be a vacuum leak or a stuck iac because even with the throttle stop backed out completely the engine still idles. I'm going to fix the vacuum leak first and then look into the rest of your post. Oh and the tps is set at .54 and I have tried with maf unplugged.

83 Crossfire TA

iTrader: (2)

lean at idle will cause surging but will also usually cause a backfire on tip in...

most surging at idle problems I've seen have been ignition and/or idle setting problems (too low, the IAC can't control it, too high and the engine thinks you're opening the throttle and starts advancing the timing causing it to surge).

ASE doc

Hey ATX, You perform the smoke test with the engine off, much like you did with the cigar. Cute trick by the way. The smoke machine simply supplies alot more smoke at more consistant pressure. I apologize for my misunderstanding. I thought when you mentioned smoke, you were talking about a smoke machine. I had to reread your thread for clarification. A decent smoke machine, like my MAC leak attack, is about $1100. If you dont already have one, I dont expect you to get one.

What I would like to know is your Block learn and Integrator numbers. What is your O2 sensor doing during this surging idle. In 20 years as a diagnostic specialist on GM vehicles I have diagnosed and repaired 100s of lean conditions on MAF vehicles. Few of which also backfired. I am not saying your issue is not ignition related. Simply that we need to eliminate lean condition first as this is the most common cause of your complaint.

Again, I did not read your thread well enough at the start. I just noticed your mention of "ESC". Understand that "ESC"(electronic spark control) refers to the knock sensor and system. What I think you mean to say is "EST"(electronic spark timing), which refers to the electronic distributor ignition and ECM timing control. The fact that your problem goes away when EST is disabled is very important. As is the fact that advance is at 55 degrees with it connected.

Please try to get hold of a scanner if you can. Do you have a friend who might have one? What you need is an old Tech1 or any OBDI scanner with GM software and the 12 pin GM ALDL connector. What I think you may have is a short in your EST circuit. You may also just have a bad ignition module. Using a scanner to eliminate lean condition as a possible cause is a good start anyway. We can also see what advance the ECM is seeing.

Knowing what the ECM is seeing and what it is commanding is vital to any drivability diagnosis. Unless we just want to guess and throw parts. A scanner gets us inside the ECM. Thats why its a vital tool for any of us who diagnose and repair computer controlled vehicles. One good scanner for these older vehicles is the Snap On MT2500, commonly known as the "Brick". Theyre discontinued and are available for $300 or so on Ebay, etc.

y84pauloflondon

Just "thinking out of the box".....last summer I too had a surging problem turned out to be a weak battery. It started up just fine,it just couldn't handle much load at idle, a new battery fixed that problem.

What the others have mentioned is most likely your problem! I just wanted you to consider checking your battery too before spending big money $$$.

turbinator3

lest we forget the old leaking fuel pressure regulator diaphragm!

ASE doc

Thats an excellent point. Have you checked fuel pressure. Low fuel pressure will cause a lean condition just as well as unmetered air.

tommygun

I have the exact same problem, I disconnect the EST and the idle smooths way out (although there's still a miss.) I've changed fuel pressure diaphram, IAC, disassembled and cleaned entire throttle body/plenum/runners, cap and rotor, plugs, plugged vacuum leaks. Fuel pressure at idle was good, the scanner showed no problems with lean, etc. I have my throttle body set screw in for it to idle around 1300-1500 because it dies down at spec. Let us know what you find!

ASE doc

Any news?

ASE doc

As nutty as it may sound. Try resetting the ECM adaptives by disconnecting the battery for 30 seconds. See what that does. Its worked many times.

ATX-Iroc

The new throttle body gets here tomorrow, I've already done all the small things like resetting the ecu and testing all the sensors. Will post results tomorrow night.

ATX-Iroc

I installed the new throttle body and it didnt help much but It did help me find more vacuum leaks(brake booster hose). I can now say that I am very certain I have no vacuum leaks. The car still surges hard and revs pretty slow and rough. I can hear backfiring in the intake and the tailpipes still smell a good bit like gas like a vehicle with no cats. I guess that means try new injectors even though they ohm out good(maybe clogged)

ATX-Iroc

I continued to mess with the car today and hooked up a fuel pressure gauge to it. I was seeing about 30 with vacuum and about 37 with so I went to adjust it but it wouldnt adjust no matter which way I turned the screw. Then when I go to prime the car I hear the pump make a high pitch noise and I see the gauge is now sitting at 90. I disconnnected the return line and nothing came out so It has to be clogged or the regulator got stuck.

ASE doc

The low pressure when running, and the fact that you couldnt adjust it up, is very telling. I think youre going to end up replacing your fuel pump. Try the running test again. This time remove the return line and place it in a container. Watch fuel pressure and for fuel flowing out from the return line. If pressure does not reach 40psi without fuel flowing from the return, then replace the pump. If you cannot acheive 40psi and fuel flows from the return, replace the regulator. Keep us posted.

ATX-Iroc

Stock FPR is back on and fuel pressure sits at 42 and 36. The old diaphragm looked really worn. the bolt holes were elongated and it looked all wrinkled like it was stretched too far. I took off the belts to see if maybe the accesories were a problem but no success. I blocked off the IAC with a paper towl in the passage and can get a relatively steady but rough idle. what else is there, I cant think of nothin but injectors at the moment

ASE doc

It may be injectors. There are alot of guys having issues similar to yours replaciing injectors. I wish you could check datastream first though just to be sure. At any rate, as hot as the underhood gets on these cars and the way the injectors are buried under the runners, its not a bad idea to swap in new injectors anyway. Bosch IIIs seem to be a good way to go and theyre relatively cheap. Southbay will hook you up. Look for them here on 3rd gen.

And about the high underhood temps, look closely at my avatar. Functional hood louvers. They work really well too.

ATX-Iroc

I replaced the injectors with some bosch IIs and the car runs alot better but still has a little surge to it. It only jumps about 100 rpms now but still has a stumble maybe once a minute. I will admit that I dont have the mat sensor plugged in because the the wire to the connector broke. I will be fixing that within the next day or two. And if that dont work I will be on the search for a scanner.

ASE doc

Cool. Sounds like youre making progress.

y84pauloflondon

[quote=ATX-Iroc;4606512]I replaced the injectors with some bosch IIs and the car runs alot better....... quote]
Bosch II's or do you mean Bosch III's???? Did you replace ALL injectors or just Some of them? You did say that you had done a ohm test the on the inj., right??

ATX-Iroc

Yes bosch II. They're off an 01 stang but are pratically new ( the stang got modded the minute it left the deealer). My old ones ohmed fine but when I took them off most were missing pintle caps so they were due to be replaced and I did replace all of them.

ASE doc

Now that you have new injectors, I would really, really like to see what you find on datastream. The high advance at idle makes me wonder what the ECM is seeing from various sensors. It may well be getting erronious data from the TPS causing it to think it wants to accelerate. Or there could be an issue with the EST. What are the O2 sensor, BLM and Integrator doing? Without looking at data, we have no idea what the ECM is actually seeing. This makes it hard to know why its behaving this way.

StevenB L98/LS1

Did you try a new distributor? Remans are about 100 bucks for our cars compared to 300 bucks for a new one. My car when i first got it was surging and not wanting to idle at all. I changed the magnetic pick up coil in the distributor no change, ended up being the distributor itself was just simple bad. Changed it out, and idled like dream after that. If you already checked you tps, and iac then the only thing i can think of to tell is get your O2 checked out.

ATX-Iroc

the distributor is a reman from about 6 months ago but i do have another I can swap in and try.

StevenB L98/LS1

It very well could have gone bad considering it is a reman i can tell you because i sell auto parts for advance a lot of remans are 50/50 type deal, sometimes you get a great ones, a lot were never made on a good day and go bad or never worked.

ATX-Iroc

Its fixed. I put in my spare distributor and she idles right and has the power. I did notice that the reman had a completely different style pickup coil. Thank god its over.

ASE doc

Thats great! Another case closed.

tunedport77bird

would your car surge at cruising speeds, i seem to have the same problem but it surges at cruising speeds also. thanks

ATX-Iroc

yes it did it surged all the time. It got a little better when I unplugged the est but that was due to the reduced timing. Dont buy a cardone reman distributor. You would be better off pulling one from a junkyard, If you are going to buy a new one get an ac delco or aftermarket.

tunedport77bird

well i have replaced the distributor, plugs, wires, cap, rotor, mass air, O2 sensor and it still surges. it has code 34 and 44. i dont know what to do now. any more suggestions would be greatly appriciated.

ATX-Iroc

Check for vacuum leaks with the cigar trick I posted above. Check fuel pressure and see what base timing is and then check what total timing is and test your injectors. What distributor did you put in it?

ASE doc

The 91 doesnt use a mass air flow sensor, it is speed density. Are you sure you have a 91 system? Code 34 is either MAF signal low voltage or MAP signal low voltage, depending on which system you have. 44 is lean exhaust. Code 34 and 44 are buddies. They tend to hang out together. Low MAF or MAP voltage will cause the engine to run lean, causing code 44 and the surging youre experiencing.

You need to get hold of a good service manual or access Mitchell On Demand or All Data at your local library and follow the diagnostic flow chart for code 34. Youll need a DVOM and preferrably a scanner. Assuming the installer of your engine included the ALDL.

tunedport77bird

this is a 89 GTA that i am working on, my 77 bird has a 91 tpi and runs perfect. this is my first 3rd gen i quit some time if i can get it running like it is supposed to ill love it. were is the plug for the distributor at on this car so i can check the timing, sorry i just cant remember. i just bought this GTA, it has hail damage, but the prev. owner put in new leather, new rotors and pads, windshield, complete stereo system. i gave only $2000.00 for the car. i am going to put a power bulge formula hood on it and a 91 t/a rear spoiler. thanks for any info you can give.

ATX-Iroc

theres a tan wire sticking out of the wire loom that goes above the a/c box that you unplug to check base timing.

StevenB L98/LS1

Check your injectors, test them and see what they say. i believe if below 12 they are bad. If you did everything check out the maf. good luck

ASE doc

Sorry for the misunderstanding. Some more basics to check, besides injectors. Look for any intake air leaks, for instance check the PCV hose. Check fuel pressure, should be 35-40 at idle. Get hold of a scanner if you can and look at coolant temp on data, does it seem right. Watch MAF voltage as you drive the car. It should reach 4.2v at full throttle. Just some ideas.

tunedport77bird

my fuel presure gauge is broke so havent been able to test it. but i have 3 injectors on the left bank that are bad. one reads 5.6, 10.1, and 11.0, all others are at 17.0 ohms. are 305 and 350 injectors the same? i have a set out of my 305 that are good. thanks

ASE doc

No. 305 uses 19lb, 350 uses 22lb. Best to replace all together anyway as they are available in a flow matched set. I hear that Southbay has a great deal on Bosch IIIs which are a good choice, about $200 for the set.