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Discussion Starter #1
I have been searching all over and cant find a similar problem anyone has had. I quit driving my tbird a while back when my frump pump seal on tranny started to leak. I went to move it from my car port to pasture by my shop and it cranks up just fine no long start or hesitation. After it runs for about 45 seconds it just dies like somebody cut off fuel, now when it dies if you try to crank it, it starts up for about half a sec then dies same thing like its lost fuel. I first thought it was fuel issue but I checked pressure on rail, sits at 36 no leaking down. I popped off ccrm and jumped a wire on relay to fuel pump to make sure it wasnt getting hot and shutting off but same thing. Now what is stumping me is if i let the car sit for for a while it will crank back up and run again for 30-45 seconds. I cant for the life of me find out what would cause it to run longer after sitting, its not near enough time for motor to even get warm so not sure what is going on. Also a note i can have pedal almost floored at 4500 rpm and after 30-45 seconds it will still just die like its lost all gas or like a kill switch is being hit.
 

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Okay you've got fuel at the rail when it doesn't start. How about spark at a plug when it doesn't start?

Failing ignition modules sometimes act like what you've described.
 

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Discussion Starter #3
I believe it does since it does crank up again but only for a very very brief moment. Would it not just turn over and not start if it wasnt getting fire? I will have to test this when it is light out since it is no longer under my carport or in my shop to see. I can take a video to show exactly what it is doing. I just cranked it to see if maybe the icm was getting hot but was cold to touch when car dies. I did notice what sounds like a vacuum leak directly behind top of motor or might just be my mind playing tricks on me but was unable to locate it. I know this could cause it to die but not sure that would cause it to only crank after sitting for a bit
 

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Ignition modules have been known to act like what you've described. Once they reach a certain temp. they stop working. Then when they cool off the car will run again until that temp. comes up again...

Also, considering vacuum leaks... There's a good size vacuum t on the intake manifold that is prone to leak on 95's.

IIRC it's about in the middle of the manifold but more on the pass. side cylinder bank. It's kind'a buried in there so you'll have to search for it. It's a big enough t that if it's rotting off one of the nipples it could cause intermittent engine dies/no start issues. You should be able to hear that one leaking.
 

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Discussion Starter #6
I have used my scanner on it and only code i can get is a code on TCC solenoid in tranmission, that code has been showing since i swapped in this tranny though and i drove it for months no problem before this. I can also only get this code to pull while running and goes away when it dies.

Here are a couple videos i just took. 2nd one i let it set for a few minutes after first video before cranking again.

https://www.youtube.com/watch?v=T2JuAix6IKA
https://www.youtube.com/watch?v=9KdqlfES3hI
 

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Discussion Starter #7
I got to looking real close and I dont suppose IAC is supposed to have this massive crack along where it seals does it. Is there an open and closed loop for the IAC when the motor hits a certain temp like you have with the MAF?


http://imgur.com/pvB3wNm
 

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It looks like that IAC hold down ear is cracked clean through. I'd replace that.

The IAC motor is an output device not a sensor. The ECT is the main sensor that tells the PCM when to go into closed loop.
 

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sounds like when it exits open loop (which takes approximately 30-45s) and then attempts to use the MAF/O2 sensors it is dying out, likely due to an incorrect fuel calculation.

Rushton Racing, The ECT is only one sensor used in the fueling status flag. After a timer/table expires, the system switches into closed loop because the oxygen sensor are heated and allows closed-loop fueling without having to wait for the engine to come up to temperature.
 

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Discussion Starter #10
Well i was taking my iac valve off and that little ear was indeed snapped all the way through and i ended up losing the bolt and tab and was unable to locate it. Swept through about 20 times with magnet and unable to find it. Anyone know the pitch of this bolt? Its a 5/16. Also if this doesnt fix the problem my next step would be the maf or 0xygen sensors?
 

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guitarmaestro said:
Rushton Racing, The ECT is only one sensor used in the fueling status flag. After a timer/table expires, the system switches into closed loop because the oxygen sensor are heated and allows closed-loop fueling without having to wait for the engine to come up to temperature.
Interesting gm. Always enjoy reading your in depth posts written with conviction.:cool: ...Knee'ill to Gen. Zod lol

So back to the op's problem. What you're saying is once that timer elapses, and the PCM is ready for inputs from the O2/MAF sensors the car dies? And it is not an ignition problem.

So in the no-start condition you have fuel, spark...would noid lights blink?

I appreciate your replies. I have learned a lot from you.

Hope that new IAC motor helps unzem:)
 

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Interesting gm. Always enjoy reading your in depth posts written with conviction.:cool: ...Knee'ill to Gen. Zod lol

So back to the op's problem. What you're saying is once that timer elapses, and the PCM is ready for inputs from the O2/MAF sensors the car dies? And it is not an ignition problem.

So in the no-start condition you have fuel, spark...would noid lights blink?

I appreciate your replies. I have learned a lot from you.

Hope that new IAC motor helps unzem:)
Yup....and especially if the maf signal is somehow compromised, everything gets thrown off including spark, because spark tables depend on knowing accurate engine load.
 

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Yup....and especially if the maf signal is somehow compromised, everything gets thrown off including spark, because spark tables depend on knowing accurate engine load.
Awesome.

So noid lights would blink?
 

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Discussion Starter #14
Picked up a new bolt at local parts store, now waiting for iac valve to come in, should be here within an hour and will pop it on and give yall an update
 

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Discussion Starter #15
Replaced iac and no luck, no cel light coming on the dash either. Going to try to check a couple other things but i really dont know what else to do than throw parts at it until i find whats wrong.
 

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Don't know if it has been brought up yet but try unplugging the MAF and running it. Simple check dose not cost a dime
 

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Discussion Starter #17
Unplugging maf was one of the first things i tried but sadly didnt change anything. It did finally throwme a code when i cranked it this time. P0102 OBD Trouble Code. But would unplugging the maf bypass this problem and allow it to at least run, very rough but at least run without dying
 

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guitarmaestro said:
...fueling status flag. After a timer/table expires
This leads me to believe it could be the PCM?

...sidenote:

'95 pcm's are known to hang the injectors. Could this be something similar?
 

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Discussion Starter #19

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Crunch time!
 
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