nbrittenham

Hello all, forgive me if this is a dumb question, but I'm stuck and in need of assistance. About a month ago I bought a 1990 Pontiac Firebird and it started stalling anytime the throttle was depressed quickly. I took it to a buddy who said to change the tps. I put a new one in and it fixed the problem but then the check engine light came on. After testing the voltages it turned out that the tps was defective and I replaced it yet again, this time with a good on. Problem is that now the car is doing the same thing as before and actually seems to be getting worse, as now it dies while stopped at intersections, is hard to restart, and has been idleing low in neutral something it never did before. So far I've changed the tps, spark plugs, fuel filter, and tested vacuum lines, and fuel pressure. I also welded shut some holes the previous owner drilled into the exhaust pipe to make the car louder. Now I'm basically at a loss as to where to go from here. Any help would be greatly appreciated, thanks.

antares57

iTrader: (8)

Have you checked or replaced the Idle Air Control (IAC) valve or disconnected your battery recently? Take a look at the below or do a search on "IAC". Good luck.

https://www.thirdgen.org/forums/v6/6...bird-3-1l.html

Base91

iTrader: (1)

Plus check the injectors and fuel pressure regulator as well as the iac. You need to start with good injectors.

nbrittenham

Sorry its been a while since I posted, and thanks for your replies. I don't know if this is the prblem but when I was going to get a noid light the fuel pump gave up the ghost. I'm going to try puttingin a new one and see if that solves the problem. If not then I'll go from there. Either way I'll post again and let you know if it fixes it. Thanks

nbrittenham

Well, I finally got my fuel pump changed! It didn't really slve the forementioned problem, but its definately not as bad as it was. If nothing else I guess now the fuel pump can be ruled out. Now I'll start to test the injectors and so forth if anyone has any suggestions I'd certainly appreciate it. Thanks

project89

iTrader: (1)

since u had the battery unhooked to change the fuel pump, u now need to redo the idle relearn procedure.

do that and see how it runs.

does it have any codes?

nbrittenham

I did the relearn, the car still does the same thing. I've noticed also that if you tap the gas pedal a few times the car will choke and die. Its not throwing any codes at all, just the sytem check code 12. Essentially changing the fuel pump just restored the car to its former state of disrepair. Incidentally when I changed the fuel pump out I found the former owner tore the filler neck seal off, I've been unable to find a new one, could this possibly be the cause?


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nbrittenham

well I took the old car to my mechanic the other day as I'm out of ideas, it basically stumped him too. He thought maybe it was the pcv, or o2 sensor so he changed them out, ultimately neither helped. He also ended up finding a crack in my radiator and installed a new one, but again it didnt fix anything. The only thing that did change was that since the new o2sensor was put in my gas milage has increased slightly. So now Im right back where I started... Minus 400 bucks that is.


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evilemokid94

iTrader: (6)

Is your tps adjusted correctly? .55 VDC at closed throttle?

antares57

iTrader: (8)

My '91 Firebird was doing something very similar. I changed out the IAC, TPS, MAP, spark plugs/wires and replaced all vacuum hoses before I got mine running right. Now when I punch it...it goes, doesn't die unless it runs out of gas and I don't let that happen. Good luck.

nbrittenham

So today as always I was messing with car when I discovered that the vacuum reservoir has been bypassed! What are the odds this is the cause of all this? I'm thinkin regardless I should probably get a new one and hook it up, i figure if gm put it in then it needs it. Heres hoping.


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nbrittenham

I think I may be onto something while cecking the vacuum line I found a giant leak at the brake booster. I fixed that one but im sure I'll find more I'm just going to replace all the lines and see if that helps.


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nbrittenham

Well, I've replaced all the vacuum lines and the car is better, but not fixed. I also found a small hole in the exhaust pipe just before the cat. I welded it closed and patched a piece of cancer on the floor pan while I was at it. Sadly none of this has fixed the primary stalling problem, but they needed to be fixed anyway. Actully after I fixed the exhaust I did notice that it is harder to stall the car, as before you could cause it to stall by feathering the gas pedal in neutral, and it still will it's significantly harder to do. In drive it still stalls the same as always when you step on the gas to quickly. I'm thinking maybe I might try another IAC just to see if that helps. I could not be more frustrated than I am right now that's for sure. I have the distinct feeling that in the end it's going to be something small that's causing this whole thing.

nbrittenham

I'm wondering if perhaps its a bad catalytic converter, I dont smell the rotten egg smell, but as friend of mine pointed out it could be bad anyway with the performance issues I'm experiencing. I'm going to try putting a new one on and see if it fixes it. If it works I'll update again so hopefuly nobody else has to go through this like I am. Regardless when I figure it out I'll report the findings so others with this problem can fix their 3.1s.


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91camrors

Back in 2008 my 91 camaro rs Was doing the same thing, Had the 3.1l auto trans.

It seemed like it was a fuel problem because it would run pretty good then when you would get hard on the throttle it would die out and be hard to start.

I replaced fuel pump, fuel lines, injectors and it seems like it got better than started getting worse. I replaced iac and still didnt really solve the problem. after months of work and quite a few dollars we finally fixed the problem. by buddy had a 1990 firebird with the 3.1l we swapped out distributors and mine ran amazing finally. His wouldnt stay running very well. I had replaced all the internals in the distributor but in never fixed the distributor. Bought a brand new distributor and the cars still running amazing to this day. Your symptoms are the same as mine were.

really hope this helps

nbrittenham

Thanks, I would never have thought to change the distributer out. I'm going to try t change it out tomorrow and see what happens. Thanks for you suggestion.


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91camrors

Not a problem just let me know, when the distributor gets warm it can make timing jump when they go bad. a little bit of corrosion or even a little bit of play really dosent set well with the 3.1l

just keep me posted

nbrittenham

Well I changed out the distributer, bought a nice msd and after everything it got me nowhere. Unfortunately neither did changing the cat out. The car acts exactly the same way as it did before. I'm completely out of ideas now. Thanks for your idea though if nothing else I now know that the problem was not caused by the distributer. Sadly the search will have to continue.


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nbrittenham

incidentally i also noticed that my oil pressure gauge is maxed out as soon as the key is turned on, regardless of if the motor is on or not.


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91camrors

Really?? your symptoms were just like mine. I just picked up another camaro today its pretty much doing the same. Cant figure it out either. Have you checked all your vaccum lines. I know 1 line can cause a mess of trouble

nbrittenham

I've been over ever vacuum line on the car at least 10 times now, but I'm going to check everything again. I wa talking to a buddy of mine that has a few on these cars and he mentioned that he had a camero once that wa ding the exact same thing. As it turned out he replaced sensor after sensor until out of despiration he changed his map sensor. apearantly this completely fixed the car. I figure what the heck im going to give it a try and see how it goes


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armos

Make sure the vacuum to the fuel regulator is good, and make sure it isn't able to suck fuel out of it. That can be caused by a bad regulator and it also lets unmetered fuel into the intake.
Check fuel pressure at key on, idling, and when you open the throttle. Fuel pressure should vary in relation to manifold pressure. It should jump a few psi when you open the throttle, you could watch for that if you have a gauge.

Make sure you have good vacuum to the MAP sensor. If you're in doubt, try a fresh rubber hose on it just to be sure. It needs to see accurate manifold vacuum.
Try unplugging the MAP sensor. If it runs better unplugged, I'd replace the MAP.

89-bird

Did you replace the cap and rotor when you put in the new distributer ? My car has been acting up and has not sounded right since I gave it a tuneup . It finally got to where it was spitting and sputtering under acceleration and then it finally stalled out and would not restart until you let it sit for a few and it ran like crap . I checked everything I could and I found that I wasn't getting spark to the plugs all the time . The rotor was not sending spark out the cap as the coil was firing and arcing inside the rotor . Everything looked good at a quick glance but under further inspection you could see the carbon tracking on the rotor . I replaced it and the cap and the car fired right up and sounds like it did about six months ago before I did the tuneup .

nbrittenham

The cap and rotor are brand new. I know when I looked at the old cap it was pretty bad, so when I bought the new distributer I got brand new internals and a cap as I didn't want to put old parts on a new part. If anyone knows what size hose goes from the map to the plenum I'd be very greatful. The one that is currently on the map is a pretty small diameter plastic tube that seams to have some sort of adapter on the ends to link up to the plenum and the map. I'm thinking about getting a bigger piece of hose and see if that changes anything, but I don't want to change the hose out if it is supposed to be that smaller one.

nbrittenham

Today while tinkering with the car I went ahead and disconnected the map sensor. It seemed to me like it made the car idle a little better, and it was much harder to kill in neutral by feathering the throttle. Something tells me this could be the culpret.


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dontellmymom

Was it the MAP sensor? Surely not all of that was caused by the MAP sensor, right?

nbrittenham

Well I must appologize I've been a little busy and have been unable to work on the car, nor update. That said I'm going to try the new sensor today. On that note @dontelmymom the map sensor (manifold absolute pressure sensor) basically uses the vaccum in the manifold to set the amount fuel going in. I'm truely not sure if its the end all be all problem with the car, but I'm sure it part of the greater problem. Time will tell, regardless when I figure it out I'm going to post the results to make things easier for others with this problem as I'm sure I can't be the only one with this issue.


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nbrittenham

Well it definitely isn't the map sensor, the car idles slightly better now but drives the same. So much for that, back to diagnostics I guess.


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Darendoover

i have the exact same car as you same year and motor and i have literly done everything you have done exactly everything... i took it to a shop and they ran a diagnostics tes and they said that my computer is bad that the PROM is fighting the EME i belive correct me if im wrong...but he said you cant get another compputer and you cant just hook another one up... im not sure if its true or not but one other thing is i have the same problem with my oil pressure gauge... i know my oil pressure isnt above 80 or my motor would have been toast by now...the only time it works is sometimes when its warmed up and has been drove a long distance and even still its wrong because the needle maxes at 80 and when i hit the gas it goes down to around 40... does anyone think there could be a leak or something? also it dosent just sputter when i brake if i let off gas period it sputters and at anytime even when its cold and im around 1500rpms i can hear a miss fire

nbrittenham

I think you can actually replace the ecm and prom I've seen the for sale on the internet. Ifthats the problem or what they told at the shop I would maybe look into getting new ones. As for my car the only thing keeping me from selling it is the fact that no one would buy it like this! I'm so completely out of ideas I'm just going to have to bite the bullet and take it to a shop, maybe they can figure it out. I think before I take it I might try to get one of those aldl cables and some monitoring software and see if it shows anything.


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nbrittenham

well just an update the car is still in its state of useful disrepair, I recently had to replace the battery, but aside from that nothing new has happened. I will update when and if I ever find a solution.


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nbrittenham

well i just wanted to update, absolutely nothing has changed. Today I tried the cigar trick hoping it would pin point a massive vacuum leak or something, but alas it didn't. I did go ahead and make a short video on what its doing which I'll include as well.


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nbrittenham

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fasteddi

iTrader: (2)

Wow thats pretty bad there.

I didnt follow the whole post but you did make sure that your fuel pressure is what it is suppose to be?? Sounds like it just wants to die as soon as some fuel is needed.

RBob

iTrader: (1)

Looks like the injector coils are shorting out. As the injector PW gets larger the ECM can no longer drive the injectors and the engine starves for fuel.

You can check the resistance of the injectors, but if they are the original injectors have another set ready to put in. Need to remove the plenum to measure each one.

Any injector that is under 12.0 ohms is bad.

It also wouldn't hurt to get a scan tool on it and check the sensor values. If some of them are screwy the ECM may be bad.

RBob.

nbrittenham

Thanks for the great advice i'll do that this week and see what happens.


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nbrittenham

So a little update on the car I replaced the injectors with some i got in thejunk yard. This actually helped the car with some accelleration issues, but the car still stalls when you romp on the gas pedel. It does how ever accellerate well on the freeway, and the lag time between when you press the gas and when the car responds is slightly better.


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RBob

iTrader: (1)

Were these JY injectors direct replacements? IOW, Multecs from another 3.1l engine. If so, some of them may be bad.

If not, they may not be the correct flow rate.

Re-reading this thread the one item I didn't see mentioned is the EGR valve. If one of the pintles is stuck open, or just plain sticky that will cause all kinds of strange problems. Although, it usually affects idle the most.

It is easy to make a small metal block off plate to go between the EGR tube and the intake manifold flange. Note that during coasting the SES and an EGR code will likely be set when this is done. But at least you can see if it makes a difference.

RBob.

nbrittenham

So a quick update, today a buddy of mine who happens to own the same car as me stopped by and we tried putting his three day old injectors with fuel rail into my car. Predictably it allowed the car to achieve higher speeds, but th underlaying problems remained. I'm going to go out on a limb and assume the injectors are not the issue. That said I think tomorrow I'll try blocking off the EGR and see what happens. Thanks for the advice and as usuall when i figure it out I'll let everyone know.


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Armored91Camaro

Have you tried replacing the MAT (Manifold Air Temp Sensor)? On my 91 camaro if i press the pedal to the floor the car would act as if it was getting no fuel. I replaced my MAT sensor and I has been running good for 3 months with no hickups. Also measure the ohms on you fuel pump relay. If you see less than 50 ohms replace it. Im running 17lbs fuel injectors from a 94 3.4L camaro with stock 3.1L tune 7730 ecm and still get 27-30mpg. Just some info if needed. I use the ALDL CABLE, and EFI LIVE V4 Pro. it works waunders, you have to use to 1990Z24.xml to read my ecm its weird i know but it works.

nbrittenham

I'll have to replace the MAT sensor, thanks for the tip! I just finished welding up a high flow cat thinking that maybe that was the issue. Naturally it was not but perhaps the MAT will solve my woes.


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2007xl50

let us know how that works. I have not had time to mes with my car, but I'm looking for direction on my issue as well. Yours is a bit differant, but kinda close to what mine does

nbrittenham

Just a quick update on the car, I replaced the MAT sensor which had no effect on thecar, but while looking around i noticed the coolant temp sensor was not actually in the motor the previous owner put a plug were the cts went then laid the cts on the engine block. I pulled th plug and put a new cts in. What a difference! The car no longer stalls taking off from a stop! I have noticed the car is suggish on the freeway now though it seems like the car wont achieve the same rpms it did before, like it wont kick into passing gear all of a sudden. I tried putting the old one in and the car returned back to its old ways. I'm wondering if the new cts is just bad, I may try getting another one and see if it fixes it. Thanks for all the help guys and as always i'll reort any changes in the future.


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Armored91Camaro

Just be careful, i have tried replacing the coolant temp sensor (temp sender switch) on the driver side head of the motor and when i do the new causes the temp gauge to be pegged out in the red zone for 5mins before the fan kicks on. I had this happen on my 89 and on my 91. If you your referring to the CTS that in mounted on the INTAKE under the throttle body, stay away from BWD always go with acdelco it is the only product that has seemed to never fail at giving the correct readings. I work at Advance Auto parts so i have lots of time to play with different sensors. Also since yours is a 1990 yours could be one of the ones that has the bosch sensor beside the CTS on the intake also known as the fuel injection thermal / timing switch. If so good luck on finding one. My 1989 camaro had it and caused al sorts of issues, then i bought one off of Rockauto, you have to go under a 1988 to find it part # is BOSCH Part # 0280130229 Thermo-Time Switch. Just keep us updated.

Armored91Camaro

I also just read you might think its the egr valve, it is a possibility, last night coming home a guy i worked with wanted to see how much of a difference the 1/8" plenum spacers i made, make on my car so i said ok, anyways right before i got onto GA 400 i was at a redlight, well when i took off it started that stupid jerking/lugging crap again, and i had it matted to the floor and the car was just burpin/slurpin/pukin/sputtering and then it took off like a rocket so i waited til he caught up and got beside me, slammed it into 3rd gear redline then to forth all the way to 100 and backed off and slow it self down to 70mph while still in forth gear, then BOOM Service Engine Soon light came on, and i said about time now i figure out why its jerking around CODE 32 DIGITAL EGR VALVE. go figure lol, so i figured i would pass this on.

Armored91Camaro

Also just found this on ebay i believe you have digital egr not sure, but if so goto ebay and type in 17091147, it brings up an new ACDELCO EGR Digital for 89.99 instead of paying 150.00-250.00 lol

nbrittenham

Just a quick update, I put in a new CTS yeserday along with a new IAT and a thermostat and wow its like a completely different car! It still hesitates a little when coming off a stop a little, but it doesnt stall anymore. I can actually drive the speed limit on the freeway now without pushing the pedel all the way to the floor, and I have my passing gear is back. im afraid to speak too soon, but as of now I think the car is doing way better, I'll drive it around for a while and see if anything changes, if so I'll report back. Thanks for all your help everyone!


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RBob

iTrader: (1)

Good deal, it is likely a good time to do an idle learn on it. That should/may help with the off-idle stumble.

See what you can do about getting a scan tool. That would have shown the CTS reading wasn't correct. If you have a laptop can use Tuner Pro RT and an ALDL cable.

RBob.

nbrittenham

Thanks for all the great advice. I'm currently looking for a good aldl scanner that can go to my laptop. I am also looking at the idle learn procedures again as I have a feeling I've not been doing it right. At any rate the car is runnin so much better, and I've already trippled my gas mileage! Anyway thank you everyone who offered advice I don't know what I would have done without your help.


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anthonybidlen67

how much did that cost? my 1990 firebird 3.1 automatic has been doing the same thing. it runs good till im stopped at a stop light for a while i have to tap the gas for it not to die