1991 GTA! HELP! CAR DIES AFTER 15 MINS!

A little new here, I just purchased a 1991 formula firebird 305, my buddy just pruchased a 1991 GTA.
We made the switch from Gti vr6’s and honda preludes and we must
appologize for straying from american muscle, i have no idea what we where thinking.
My 305 tbi runs great, and is in great shape, his GTA is ablsolutly perfect no rust or rot 305 TPI.
Unfortunately his TPI engine runs for 15 mins the stops when it gets warm, then its hard to start untill the car cools down. He spent a tonne of money trying to fix problem and is getting very discuraged.
He replaced, ignition coil, Water temp sensor, added a hypertech chip to manage fuel better, just throwing money at it and nobody can come close to answering the problem.
The mechanic seems to think it is some sort of injector signal or distributor signal.
ANY IDEAS? (my friend and I don’t hang with D-trump if you know what i mean, we have to stop throwing money at it.)
Thanks guys!
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I'd take the hypertech chip out until you've fixed the issue. It's not going to manage fuel any better. I'd suspect the ignition module. It's in the distributor. If you remove it, you can take it to autozone and they have a tester that isn't very reliable but if it fails several times, you have a better idea that the module is bad. I've had bad ones test good and good ones test bad on occasion so have them run the test 4-5 times.
-Bruce
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Check the oil pressure switch & connections just above the oil filter. The switch powers the fuel pump after startup. If the oil pressure drops too far when the engine warms up the switch will shut down the fuel pump. Check the oil pressure with a gauge if bypassing the switch lets the engine stay running. If it is fine (above 10 psi at idle hot) change the switch. If it is low....repost.

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You're partially right, the oil pressure switch does power the fuel pump circuit but the fuel pump relay does too. If the fuel pump relay is working, then the oil pressure switch is redundant. You've kinda got it backwards, the reason they have the oil pressure switch is to power the fuel pump if its relay goes out and you won't be left stranded. You're right, though, if pressure drops too low (I was thinking more on the order of like 5psi or less) then the oil pressure switch will open.
-Bruce
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I seriously doubt it's the computer because it runs. Did you ever try replacing the ignition module?
What's the symptom when it stops running? no spark? no fuel? Obviously you're getting compression or it wouldn't run at all. If you need a computer, let me know. I have one that I bought a while back to troubleshoot with and I've been meaning to put it on ebay to sell. I'm sure we can work something out.
-Bruce
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"" wrote:
> > > "redshirt" wrote: > > > Thanks! I'll try that, > > > > > > I emailed hypertech, incase any body would think > otherwise,,, > > > the 5.0 tpi chip is much different than the 5.7 tpi chip. > > > > > > my mechanic seemed to think they would be the same. he was > > > wrong. > > > > > > Thanks for the help so far! > > > > We replaced the hyperchip with a stock replacement chip > ordered from > > texas. > > > > Still same problem. after 100 it shuts down untill it hits > 40 degrees. > > > > Man we have tried everything! > > > > This car just won't stay running! > > > > I think we wil try to replace the entire computer. talk > about > > expensive fixes. > > I seriously doubt it's the computer because it runs. Did you > ever try > replacing the ignition module? > > What's the symptom when it stops running? no spark? no fuel? > Obviously > you're getting compression or it wouldn't run at all. If you > need a > computer, let me know. I have one that I bought a while back > to > troubleshoot with and I've been meaning to put it on ebay to > sell. I'm sure > we can work something out. > > -Bruce
a mechanic put it on a scope and said its the injector pulse.
It stops getting injector pulse but nobody can figure out why.
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"redshirt" wrote: > a mechanic put it on a scope and said its the injector pulse. > > > It stops getting injector pulse but nobody can figure out why.
Do you know what number is on the computer?
THe GTA is a 1991, with all options (automatic) apperantly if there are any differenced is the model the computer might not work properly.
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Does it also stop getting spark? As far as I understand, both spark and injector pulse is determined by the ignition module. Directly related to the ignition module is the pick up coil.
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"" wrote:
> > > > > "redshirt" wrote: > > > > > Thanks! I'll try that, > > > > > > > > > > I emailed hypertech, incase any body would think > > > otherwise,,, > > > > > the 5.0 tpi chip is much different than the 5.7 tpi > chip. > > > > > > > > > > my mechanic seemed to think they would be the same. he > was > > > > > wrong. > > > > > > > > > > Thanks for the help so far! > > > > > > > > We replaced the hyperchip with a stock replacement chip > > > ordered from > > > > texas. > > > > > > > > Still same problem. after 100 it shuts down untill it > hits > > > 40 degrees. > > > > > > > > Man we have tried everything! > > > > > > > > This car just won't stay running! > > > > > > > > I think we wil try to replace the entire computer. talk > > > about > > > > expensive fixes. > > > > > > I seriously doubt it's the computer because it runs. Did > you > > > ever try > > > replacing the ignition module? > > > > > > What's the symptom when it stops running? no spark? no > fuel? > > > Obviously > > > you're getting compression or it wouldn't run at all. If > you > > > need a > > > computer, let me know. I have one that I bought a while > back > > > to > > > troubleshoot with and I've been meaning to put it on ebay > to > > > sell. I'm sure > > > we can work something out. > > > > > > -Bruce > > > > a mechanic put it on a scope and said its the injector > pulse. > > > > > > It stops getting injector pulse but nobody can figure out > why. > > > > Does it also stop getting spark? As far as I understand, both > spark and > injector pulse is determined by the ignition module. Directly > related to > the ignition module is the pick up coil.
Yes, its still getting spark.
I think i’ll try a new ecm, as a last resort.
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Doesn't the MAF sensor control fuel pulses and pulse width? I've had a couple of cranky MAF sensors on my 88 TPI TA and it caused similar problems as yours. Odd thing was that disconnecting the MAF actually let the thing run in "limp home" mode.
Good Luck, Dave Carroll
redshirt wrote:

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In 1990, GM switched to a MAP sensor instead of using the MAF sensor.
-Bruce
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"redshirt" wrote: > A little new here, I just purchased a 1991 formula firebird > 305, my buddy just pruchased a 1991 GTA. > > We made the switch from Gti vr6's and honda preludes and we > must appologize for straying from american muscle, i have no > idea what we where thinking. > > My 305 tbi runs great, and is in great shape, his GTA is > ablsolutly perfect no rust or rot 305 TPI. > > Unfortunately his TPI engine runs for 15 mins the stops when > it gets warm, then its hard to start untill the car cools > down. He spent a tonne of money trying to fix problem and is > getting very discuraged. > > He replaced, ignition coil, Water temp sensor, added a > hypertech chip to manage fuel better, just throwing money at > it and nobody can come close to answering the problem. > > The mechanic seems to think it is some sort of injector signal > or distributor signal. > > > ANY IDEAS? (my friend and I don't hang with D-trump if you > know what i mean, we have to stop throwing money at it.) > > Thanks guys!
I am going to discconect my map sensor and my knock sensor tonight.
Lets just see what happens.
The other clue to the puzzle is that if connect the primary fan it turns on right away, without the car being at 190f.
I think the ecm is reading the sensor wrong.
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