sparky1989

I need some help, I have a 89 305 TPI that goes into limp mode when cold and sets the code 33 but once it gets up to normal operating temperature runs beautiful. I have inspected all vacuum lines except I haven't done the "spray the carb cleaner to find a leak" yet. I have followed the GM troubleshooting chart for code 33 to where it says change your MAS, so I did and nothing changed. The TPS is set correctly, the IAC I'm not so sure but I don't think it's an issue because the car runs great and the code 33 goes away when it is at operating temperature. Any ideas?

sparky1989

sorry I meant MAF not MAS, anyhow going to do the propane check.

sparky1989

I don't know if anyone is reading any of these logs, or if someone can help me but I'll post my findings, if anything it will be a good record for my personal use... today tightened all plenum bolts and propane checked hoses, intake, injectors, etc... didn't turn up anything... but I hooked up the laptop up using winALDL to the car the MAT is all over the place, -30C to 100C checked resistance of MAT all looks good 800ohms not unreasonable according to chart, therefore I troubleshooted it using code 23 chart and it points to a faulty ECM, but I have no code 23, maybe my laptop is not reading the value correctly. I may have to look into getting a proper scan tool. Still getting only code 33 and car running rough at idle when cold. Nothings says anywhere that a MAT is related to code 33 so I am still lost. HELP!!!!

sparky1989

today I removed the ECM and inspected connectors and interior of module, for any signs of damage, contamination etc... Nothing was noticed not even any burnt smells. I reconnected the ECM then I started the car and disconnected the MAT and a code 23 was set as expected, and as well the code 33 set, than I jumpered the MAT harness and all codes disapeared and the car ran good. I than hooked up my laptop and noticed the value of the MAT was still out of wack but not such a large swing as before this time it stays around 4C I would expect it to be 130C. Now I am wondering if it isn't the ECM making a wrong calculation. It would be nice to verify it with another scanner, but I don't have that option, unless I bring it to a shop.

Tony89GTA

iTrader: (7)

Maybe there is a short in the MAT wires? Also how you know it's going in limp home mode?

sparky1989

The mat wires have a 5v across them so I assume the power is leaving the ECM and returning to ground on the ECM o k. I am wondering if the delco plug wires may be inducing voltage to the mat wiring therefore I have ordered better quality plug wires and I am going to try that. I am also planning on buying a vacuum gauge because I am curious if I may still have low vacuum when the car is cold and maybe when it gets hot everything expands and seals up the leak? As far as the limp mode I assume when it starts and runs poorly than after a short time it sets the 33 code and runs better but sounds rough and smells rich. I have also ordered a ECM, iac, and tps, I have to order this stuff from the states because apparently no parts exist in Canada anymore, what a joke, I think they only want us to buy new cars but they can pry the keys to my F body from my cold dead hands

fireburdluvr85

A leak can also come from within. What I mean by that is egr solenoid leaking causing the egr to be hung open. A bad evap solenoid is another popular on. I also have an 89 with maf and that's what mine turned out to be. U can block each off temporarily to see if it helps Ur situation.

sparky1989

I bought a vacuum gauge today and plugged it into the line that leads from the plenum to the evap solenoid and ran the car, it got 16.5 in-Hg from cold up to 105C which may seem a little low for vacuum, but the interesting thing is I still had the code 33 until the engine got up to 100C then it cleared. As well my MAT was all over the place, and another note is my MAF read O g/s but I'm wondering if my laptop and software are suspect, I use WINALDL but I have to use the shorting resistor in the USB to ALDL cable and I wonder if that sends the car into limp mode. I may have to find another code reader / scan tool, but I would like to buy one that works good, and I'm not too sure which one that would be? I have watched the EGR with a camera and it stays closed so I'm thinking that is good. I am turning to ignition I checked the timing today and it was good but my timing light flashes intermitantly which makes me think maybe bad ignition? I did put new distributor wires and plugs two years back but I don't like the plug wires so I will start with replacing them here when I get them. As well there is a ignition module that I've heard a little about I may start investagating into that as well.

sparky1989

well I did compression tests on all cylinders and they were all around 140 lbs. Then I replaced the ECM, and sparkplugs and wires, and still got the code 33. I think I am in denial I must actually have a vacuum leak, I wish I knew where, in order to determine how far to tear it apart. Maybe I am going to try that smoke test you see on you tube, as for now I am gone for a week so I'll put it to rest for now...

Tony89GTA

iTrader: (7)

The 10k resistor shouldn't send the car into limp home mode. 16.5 in-hg don't seem to bad for vacuum though I could be wrong. What I'm wondering about is maf is reading 0g/s, does it do this after it warms up? How about the rest of the readings in winaldl does it all show normal? I can't see only these 2 things showing wrong and nothing else. Can you post up a recorded log file? I haven't used winaldl in probably 10 years so I kind of forgot if you can record or not.

I looked at a couple of code 33 links to find more information about it maybe they can help

https://www.thirdgen.org/forums/tpi/...code-33-a.html

https://www.thirdgen.org/forums/tech...ible-code.html

sparky1989

I changed out the EGR and still the code 33 set, then I put the old MAF in and now there is no more code 33 but it sets a code 34 just as before at higher RPM but to note I can get gps raw data from it. Here is the raw data in .txt format. The one thing I noticed is the O2 sensor is all over the place and flags rich and lean are set on and off as well, maybe O2 or another bad MAF? I was not able to get the MAF from my local auto parts store under the car information, they said there were none available anymore and that my car wasn't an IROC. Therefore I gave them the Bosch number off the MAF and they were able to order one with that information which they say is used on a Denali, maybe the new MAF is wrong or faulty? Two years ago I had the valve seals done and I changed the injectors to Bosch maybe I will go back to my rochestors and see what happens it's not that big of a job.

sparky1989

I will continue on this problem shortly...haven't had time yet. I think my next move is to verify correct adjustment on my valves. I will post my results when completed. The more I read on compression testing I believe I did it incorrectly. As well when I remove the hose to the AIR on the exhaust manifold and put my finger on the end it actually sucks air once in a while, so the exhaust is actually intaking air?!? That sounds like I messed up on the settings when I put the heads on?

sparky1989

I am still messing around with this, I have checked my valve adjustment didn't change a thing. Probably it's not related but I am changing my vapor canister and purge valve because they failed the gm service manual test. The manual says that a faulty canister or purge valve can cause poor idle and such so you never know it may be something as simple as this.

Schrade

Do you have K & N air filter? Too much oil can draw onto the MAF filament, and wreak havoc on the reading.

Are your spark plug wires properly routed? In the wire looms? If misrouted, they can cause EMI, same as a nuke, and solid state sensors don't dig on EMI interference.

Tuned Performance

iTrader: (92)

This code is set when the ecm sees a indicated airflow of greater than 45 grams per sec (gps) and the tps is less than idle, and engine rpm's is around 2000. Winaldl works not the best display for data but if its showing 0 grams per second you maf is bad. The f and y body maf from 86-89 will work despite the 2 different bosch part number. You should post in the wanted section alot of thirdgen guys up north. You can check the voltage output from the maf to confirm that the wire or connection is not bad from the maf to pin B12 of your ecm.

Schrade

That's good to slow down, post up and write up your stuff.

You think about it more, and solutions come to you.

Rodan (The Thinker) OUT!!!

sparky1989

I have stock dual snorkle and regular filters. I also have the spark plug wires routed in orginal wire looms.

sparky1989

It seems the code 33 only shows up if I leave it idle for a couple of minutes. If I get in it and drive it only shows up once in a while maybe a 5 sec flash then it clears. It'll idle good then the code 33 shows up and it starts to smell like a badly tuned small engine you know kind of dirty. I think I was using the WinALDL wrong I didn't have the correct ECM number in it therefore I will hook it up again here and get an updated measurement posted on the gps. Thanks for the additional information I will try to get back to the car here shortly but life is demanding in other areas right now. Camping, Kids, Work, Wife etc... I don't know if that's the correct order

Tuned Performance

iTrader: (92)

As soon as the ecm sets the code 33 the ecm goes into limp home mode and will run real rich.

sparky1989

I changed out the canister, fuel line purge valve and gas cap, no difference still sets the code 33. I'm kind of stumped, maybe give up get a crate motor, different injection system... 350 RAMJET?

MrPackstin

iTrader: (9)

My TPS is set to .54 w/voltmeter and WinALDL shows it is 1.06v, so this could be the problem.

What is the voltage on the green wire at MAF when disconnected?

MrPackstin

iTrader: (9)

MrPackstin

iTrader: (9)

A guy on the vette forum forgot to plug his MAF sensor in and could not tell it was unplugged.

MrPackstin

iTrader: (9)

Check what Cliff had to say here.

One guy there bought 7 MAFs, yes 7, before he got one that worked. Apparently, the aftermarket parts for these systems are horrible. I have bought 2 TPS sensors and neither will put out 5v at WOT. Moral of story is new part is not always a good part.

Tuned Performance

iTrader: (92)

It will show bogus GPS readings once your actually rpm goes up it will throw the code 33.

MrPackstin

iTrader: (9)

IF our WinALDL data is correct and GPS are all over the place it will certainly reach the criteria for 33. Just pure hell for the ECMs. Without looking I think the GPS at idle (according to TPS) if GPS reaches XX for 1 second it will set 33.

Sparky is your GPS stable in WinALDL or is this jumping about...say from 4-35? Maybe make a video of the laptop while the car is idling. You can study it then. According to Service Manual for '89 it is supposed to be 4-7.

I have found vacuum is supposed to be near 20 for our cars, BUT mine is not that high.

Maybe someone with a healthy TPI can post their vacuum reading for us....?

sparky1989

checked my vacuum today and it's at 16 so it does seem low, maybe I will tear the intake off and reseal it when I get some time. I will hook up the laptop and get a GPS reading here within the next couple of days...

sparky1989

TonyGTA89 is sending a MAF out that I will try so hopefully that will prove if my MAF is working correctly. I do suspect now days "new" parts are not the same quality as they used to be.

sparky1989

I have installed Tony's MAF and it run's beautiful, therefore the brand new one I installed for $300 was somehow different or faulty. This forum and the help of TonyGTA89 has been of tremendous value, I cannot express my appreciation for all this help. THANK-YOU!!!!!

Tony89GTA

iTrader: (7)

No problem buddy, I know how frustrating these cars can be sometimes.

Jersey89GTA

iTrader: (1)

I'm getting a stupid 33 Code (MAF), not 2000 miles on a new ... do I change it out and see what happens, pricey little devils

2firebirdpals

Good to hear the news. But I have to ask--- what were the symptoms of Limp Home Mode--- Where you topping out at -8-10 mph and stuck in what appears 1st gear. Is that Limp Home Mode ?

Tuned Performance

iTrader: (92)

You got it The check engine light will be on and the engine runs super rich.

2firebirdpals

1---How do I go about checking for Codes??
2---What pin numbers do I bridge and where will they be located- driver side or passenger.

Jersey89GTA

iTrader: (1)

Been doing some research on the MAF issues. Looks like the corvette guys see the same dilemmas with their L98s etc ...

Using the correct relays is critical. In 3rd gens they did vary from year to year and it important to use the right ones, not just a aftermarket one from local parts house, but actual GM ones. Certain types of resistors are built into the relays since the MAF is almost like a heating element. Proper voltage delivery is critical.

Going to the Chevy dealer today to see about it .., will report back.

Can't imagine that my $245 MAF is pooped out already, got to be the relay(s) going to replace both power and burn off, and the are only like $20 ...

2firebirdpals, buy yourself a code scanner that plugs in ... you will use it a zillion times, trust me, they come w/a book too for reading codes.

Sears/GM one ... $39.00 -

sparky1989

It still could be your MAF, I changed mine out with a brand new $300 one and still had the code 33. I spent all summer chasing this code 33 because I thought "it can't be the MAF it's brand new" well after wasting my summer and several hundred dollars it was the MAF. The burnoff and sensor relays on my car are the same as the radiator fan relays, I've taken them apart and they are nothing special just a set of contacts no hidden resistor, you could just swap them around to check their operation or I tested mine by removing them and applying power from a 9 Volt battery across the relays coil and measuring resistance across the contacts.

Jersey89GTA

iTrader: (1)

You are probabily right. Put the new relays in .... car wouldnt start.

Unplugged the MAF, fired right up. Put old relays back in, plugged in MAF ... Still no start, unplug MAF .... Started.

Pull MAF off, looks like one of the hair thin wires is gone ? IS there 2 thin wires or 1 ...only one I can now see.

I guess I'll try a new MAF. So much for the relay theory.

sparky1989

Here is my original MAF

Jersey89GTA

iTrader: (1)

Hey thanks for posting that pic of your MAF. Mine has wires as thin as hair, can barely see them ... I see yours has two wires, mine must be shot only has one ! Thanks that makes me feel better. Bought one about 1 year ago, noticed it was remanufactured one, (NAPA), was $148,+ 61 core charge.


Here is an interesting read on MAF relays for years 88 and less, ablurb on 88+ MAf relays also. Info is all over the place on these things.

https://www.thirdgen.org/forums/tpi/...nces-they.html

Chevy86 IROC-Z

iTrader: (17)

I had boughten a new Bosch MAF Sensor. I kept getting errors. But I found a solution that stopped my code 33. I believe it was the cause, but the terminal connectors of the weather packs where dirty. What I did was disconnect the MAF and used a small jewelers screw driver and inserted into the female connector and twisted to grind away any corrosion. As for the male connector terminals, I scraped the outside portion the metal male terminal that inverts into female connector. Then I reconnected and voila. It's been over 3 years without a hitch.

Jersey89GTA

iTrader: (1)

My connections looked clean. Turns out the old MAF had 2 wires missing, new one has 3 hair thin wires , was running great for a year, took it for a two hour cruise, stopped for fuel, restarted and threw the 33 ...

We'll see how long the new MAF lasts with the new power relay.

I might start unplugging the MAF when I disconnect/reconnect the neg batt cable - perhaps a spike in power is blowing them out ?

Chevy86 IROC-Z

iTrader: (17)

Nah. I gotta a TC 33 troubleshooting diagram somewhere. I'll post if up later when I get home.

Jersey89GTA

iTrader: (1)

Good news - put in new MAF (BTW, NAPA increased the price, was $148, now $199....), Put in new MAF and a new relay. BAM - runs great - no more Code 33.

Also was getting a 32 (EGR) put one in 1 year ago ....First EGR (in pic w/ X on it) was a NAPA - "Piece of crap" , funny cause the letters POS are stamped on it - I swear. Had to peene a washer in the bottom of it according to the instructions, compared to the original i pulled out had the large plunger that goes in the hole ... regardless, put in the correct one and now ....

CAR RUNS F'G GREAT, I feel like I hit the lottery !!!!

Thanks for all your support and thought I'd post this if you are getting a 32 and 33 code on the SES .... reman'd MAFs are crap too.

sparky1989

Hey Jersey89GTA do you know the part number of your new MAF, up here in the frozen north they say you cannot get one anymore, but I sure would like a spare one.

Jersey89GTA

iTrader: (1)

Napa has them (remans) ...


Can roll the dice on flea bay for about $100, Napa was $199, 12 month warranty.




Part Brand: Bosch

Interchange Part Number:

Manufacturer Part Number: 0 280 213 004