91 3.1 Engine Help Plz!

[fattonybob]

Ok i have 1991 3.1 Lumina with 114,000 mile on it ..on time awhile back my car would die when i shut it off and not start for a couple days...it doesn't do that anymore but after that i started it and it runs rough real rough i hae no rpm gauge to tell you what that was but it runs ruff and smells like its running rich...but not sure put i can put it in gear and try to go some where it will try to die out if i try to floor it and if i baby it it will only go about 20 to 30 miles an hour... it will stall in nutral as well i have been taking it to mechanics and they have no idea...i have replace the coil pack and egr valve i think...thats what that was...tuned it up no to long ago so i have no clue what is going on but if i let it sit for a couple days it runs Fine...perfect almost...then it dies when i get it some where and does the rough idle and stuff agian...plz help i have put too much monety in this car to junk it...new fuel rail also i forgot about that.... and i ahave good fuel pressure...plz help! oh and a used computer out of a 92 3.1 4 door but that was a couple months ago...

[jeffcoslacker]

Regardless of what else you find...it's a good bet your o2 sensor is hogged up after running it like that, I'd replace it but not until you find the problem.

I think I like a bad fuel pressure regulator as a culprit...not being able to check it out myself...

[richtazz]

Did you actually hook up a fuel pressure guage at the rail? Just because it will spray out of the schrader valve doesn't mean your fuel pressure is ok. Your symptoms are classic low fuel pressure.

[fattonybob]

No i have Good Pressure at the rail so i have idea what is going on with it i was told to day by the machinac when it runs rough....the injectors weren't pluseing correctly....but it sat for the weekend and there fine...its weird....they are confused

[comptech_69]

Does it only do it when it warms up, or does it not matter?

[fattonybob]

all the time.....

[fattonybob]

ahhhhhhhh...

[richtazz]

These cars have a high fail rate ECM, because it's mounted under the hood and exposed to the elements. If you're occasionally losing injector pulse, the ECM would be my first thing to check.

[comptech_69]

Check the system for any codes that it could be putting out. Your check engine light might not be on, but the computer dosn't trigger the light for certain codes or even intermittant ones. You might have a trouble code that you don't know about

[fattonybob]

yeah indon't think there aree any i am gunna try the ecm idea if i knew where it is...lol..i am not a mechanic...or really know about cars period...

[fattonybob]

Originally Posted by richtazz

These cars have a high fail rate ECM, because it's mounted under the hood and exposed to the elements. If you're occasionally losing injector pulse, the ECM would be my first thing to check.

I have tried that and that did not do what you described...if i hit it with a screwdriver it would stall out while idleing...but if thats the case do i have to replace the entire ECM?maybe i should check the codes?i think the place i took it to did that but i am not sure....they never said anythign about it

[tblake]

im a bit confused, if the that car stalled when you tapped the ecm, then chances are you have found the problem. considering you dont beat the shit out of the ecm with a screw driver, any idle fluctuations or stalling with a few swift taps, usually indicate a failing ECM.

[comptech_69]

Did you nosedive that car into a pond or something? Sounds like the computer gor really wet. Try unpluging all the connections and seeing if their discusting or not. If they are, clean them up and plug it back in.... Could always be a loose connection

[fattonybob]

No i didn't nose dive it into a pond...i have switched computer recently and still does it...and the ECM thing is that i tap'd it and it did not stall out it only stalls out when i try to drive...i.e hit the gas....but the mechanic told me my injector pulse weakly when it runs rough like it is now.. sorry if i am being difficult..but this thing has caused me trouble for the last month and i am nto that good with cars or terms..so i am trying to describe this as best as i can..

[richtazz]

You're not being difficult, you're being thorough. Was the replacement ECM a new or reman unit, or another used one? A used one may have the same issue your other one did. Also, if it's a used one, did you swap the prom from your original, or leave whatever prom came in it?