K.C.Kustoms

Little background-

I have a 1991 Firebird 3.1l v6, 700r4. A couple of months ago I posted on here because it would not start or idle. I found out that I had a bad fuel pump relay and that fixed this problem.

Here is the original thread:
https://www.thirdgen.org/forums/v6/6...ont-start.html

Now -

The car will now start and idle pretty well while it is in park & neutral.
The problem begins when I put it in any drive gear (Drive, Reverse, and low gears.) When I put it into these drive gears and I am at a stop the car will then start making some jerking motions forward like it is trying to accelerate and the idle will get rougher and then cut out.
It will also sometimes cut out while I am just driving normally but it is mostly when it idles in any drive gear.

So I have used the search function but couldn't really find any definitive answers. Could this be my ECM or is it my transmission torque converter or something else? (engine or transmission problem?)

I will try and get a video of this happening asap.

Thanks.

fasteddi

iTrader: (2)

No check engine light coming on??

Definitly a werid problem and a video would help alot. Can you hook a fuel pressure guage up and see what it does when you load the engine(IE. put it in drive or any gear)?

I would bet its not the trans/converter just because your engine is stumbling under a light load... in gear at a stop.

K.C.Kustoms

There was a check engine light but I forgot to say what it was.

The code was 33: High voltage (low vacuum) at mass air flow sensor (or MAP sensor)

We already replaced the MAP so I don't think its that.

I guess it might have a vacuum leak at the MAF sensor or High voltage somehow.

I haven't gotten a chance to check the fuel pressure.

The video should be uploaded shortly.

Thanks

Gumby

if your foot is on the brake when it happens, you look for vacuum leaks, the brake systems vacuum demands will choke an engine off and kill it.

K.C.Kustoms

I just checked the vacuum with my tester and it fluctuates between 9 to 12
HG. Which is pretty Low I believe.

I couldn't find any vacuum leaks. Awhile back I took off the intake top to test my injectors, could I have installed it wrong and now its leaking from that?

So, is it a vacuum issue or the MAF sensor?

fasteddi

iTrader: (2)

Wow that is low!!!! Its a vaccum leak.

17"-22" stock car should pull.

Start spraying areas including all gaskets and vac lines with carb cleaner, youll hear it idle bad and damm near die when you find the leak.

K.C.Kustoms

Well, Today I found where at least one big vacuum leak was. One of the hoses leading up to the throttle body was spliced very poorly and leaking.

We replaced that whole section of hose which made the idle sound a little bit better and our vacuum now read between 19" and 20"

I think that solved the big leaking issue, but we are still having the same stalling problem as before.

And we are still getting code 33.

Any ideas on what to do next. I'm still working on getting that video up.

Thanks for all the help so far.

dontellmymom

Did you check the O2 sensor? My 3.1 would sometime die at red lights and when I put it in reverse, until I changed the O2 sensor.

Mongo Chicken

your ECM is bad. I had the same problem and refused to believe it was the ECM so, I replaced all the sensors. twice. same problem. new ECM and it runs like a brand new one. you can get one at O'Reilly for a hundred bucks. Hope this helps...

ItstillaV6

I have a similar problem, except I am getting code 43, randomly. When I checked the code and troubleshooting guide, in my Haynes manual, it comes back as poor connectivity or open circuit with the ESC, defective knock sensor, defective CALPAK, or defective ECM.

The troubleshooting section lists the possible causes as defective fuel injectors, defective ECM, or defective fuel emissions sensors.

I have replaced the knock sensor, and there was a "slight" improvement, during my "idle learn". Now, the problem has gotten worse, and so has my fuel economy/performance. If I unplug the knock sensor, the misfire is barely noticeable, and it doesn't stall at all.

I want to check my fuel injectors, for resistance, as it is a lean condition, that is causing my code 43.

If you have any advice, I'm open to it, and will add it to my list with the injector tests.

Thanks, I appreciate it.

Gumby

All codes end with or bad ECM, can be a fun trip chasing codes that go no where.

id pull and inspect the ECM board close for any burn marks, section can fry out and the rest will work or not work right.

zacw4328

My 91 Camaro 3.1 L V6 stalled a couple days ago for the 1st time. I was stuck in traffic, pulled up some(in drive), thenbacked up some(reverse), to let someone across me, then back into drive and it just stalled.
I'm not sure exactly what caused it, but maybe it was the same thing that happened to you. Not sure though.

Mongo Chicken

Your ECM is bad. you are getting phantom codes. dont waste your money on sensors. believe me, I drove mine for two years with one foot on the break and one on the gas so it wouldnt die, refusing to believe that it was the ECM. I finally broke down and replaced it because it started shutting down the fuel pump circuit at highway speeds. A new ECM will solve your issues. trust me. I have a collection of new sensors that I cannot return.

I hope this helps.

FirebirdJim94

I am recently having the same issue! I was driving from my lunch break and hit the brakes then it shut off. The Engine light came on but i do not have a computer to read older models only 95+. So, ofcourse I have a 1991 3.1 firebird. My ECU has a Stage 1 JET performance chip. Engine has a cold hair intake, MSD ignition. How do you read the vaccuum preasure? I work on this car all the time and I am finally getting all the kinks worked out this and an oil pan are my last projects for the car until it is finished. PLEASE HELP!

fasteddi

iTrader: (2)

Look on the back of the upper intake manifold. Such as here where the ports are. You will be putting a short hose off the ports, runing that into the T fitting, hook up the stuff that was there before, and then run the new hose to the vac guage.








Get one of these and some hose like this and T it into the line so everything is still hooked up the way it was but now you have another vac line coming off.






Then either buy one or see if a local parts store will rent you a vaccum guage such as this. It must be able to read inches of Hg.


Connect it all. Start the car up and let it warm up a bit. And then look at your guage while shes idleing in park. Then you can see if the vaccum is steady and high enough.

BTW Vaccum is not pressure. Its just a vaccum. Pressure is measured in inches of water, psi, bar exc.

Mongo Chicken

to read the codes on the older ones you have to put a paper clip between the a and b ports in the black connector under your dash and turn on the key. dont start it, just turn on the key. it will flash once then twice then repeat it 2 more times. that is the self diagnostic. if there are any stored codes they will flash in the same way. if you google gm trouble codes it will give you a list of the code numbers and what they mean. if the engine light only comes on when it stalls chances are it wont show a code. pulling the ground lead off the batt for 10 seconds resets it and clears the codes. after replacing all the vacuum lines and resealing the the intake, the brake booster and every sensor on mine i found the ecm was giving me phantom codes so I replaced the ecm. 100 bucks at o'riellys runs like a brand new one now. I hope this helps

FirebirdJim94

Did some research today. Found out it is my MAP sensor. Unplugged it and the car was spinning tires all day. Just like new. Unfortunately, I forgot to latch my ws6 ram-air fiberglass hood.. So, when 95mph hit so did the hood to my windshield. Looks like I have some fiberglassing to do when it warms up outside.

fasteddi

iTrader: (2)

So your saying that you unplugged that MAP sensor and it ran perfectly fine??? But stumbles when the map sensor is hooked back up? I can see it running ok (limp home mode or fail safe mode) off the default settings preset in the memcal but i cant see it purring like a kitten. I ran my car in limp home mode and fail safe mode before when it was stock it didnt run the best it has but it did run ok.

Just my opinion but if its the map get a new one asap. There only like 40 bucks new at AZ. It cant be good at all to be tearing up the streets when the car has no idea of the load or vac on the engine.

FirebirdJim94

Well ofcourse i'm not going to run it like this forever this was just a shot to see what was wrong. I saw on a forum on here to unplug it and see how it goes. So, decided to give it a shot and it ran nice. However, I will pick one up on my way home from work tomorrow.

fasteddi

iTrader: (2)

Ok. I was saying that it cant be good to go rip up the streets doing 95mph without a Map sensor hooked up.

I remember when my car was close to stock. It took forever to hit 95mph. I almost felt bad for the poor thing even when it was running perfect.

FirebirdJim94

My 3.1 was surprisingly quick in its prime. I was able to keep up with a 2011 mustang gt until he hit 5th gear.

fasteddi

iTrader: (2)

I remember timing my Camaro. 0-100 about 30 seconds. And this was the same car that could make mid/high 16 second passes at the strip on a regular. There peppy cars to about 60mph then just fall off.

Dave Beardsley

I have a 1992 firebird.. that stalled on me I thought I tan out of gas so I went and got gas.. the car started up and ran for about 2 minutes. Then shut off on me at times it would just crank and crank and crank but not start if I pump the gas the car would start. If I accelerate the car dies.. can u please help me with this issue

FirebirdJim94

have you tried the ignition module? I had something similar happen to my 91. Went to get gas it stalled out. Replaced ignition module and nothing. The car was getting gas but little spark. It ended up being the cap and rotor. Put a new one in and the car ran fine.

miguelknight

I also have a problem and my firebird v6 1991, has a consumption of 11 mpg in the city and this tired, that does not happen, someone knows?