whitemj1948

My son has a 93 40th coupe. He had the ECM rebuilt and installed a new throttle position sensor as per the code he was getting. The code was for the TP sensor. The car started and ran perfectly for 3 days, then on the way to work the car died. Now it will start and run for about 10 seconds and die, if you move the throttle it will die immediately. Any ideas? I do have a Tech 1 tester, so what ever help you could give would be appreciated as this is his only car. Thanks in advance for any help. Mike

Kevova

Codes? Fuel pressure? Do you have factory manuals?

whitemj1948

The car is not showing any codes, fuel pressure is good and no we do not have a FSM. I have not personally worked on the car, so can not verify anything. Is it possible for the fuel pressure to drop after it starts? Thanks for any info anyone can provide. Mike

Kevova

It's possible if pump gets prime signal and not run voltage. Opening throttle adds air if engine is running lean it could cause stalling. Does engine restart easily? What is tps reading? Disconnect egr valve. Coolant temperature sensor read approximately ambient temperature when you first try start. Of course ground wires are all clean and tight. Check oil pressure switch connections also.

Tom400CFI

Kevova is on the right track here, but I wondered about this: How did you verify fuel pressure?? If you can do that...then you ought to be able to see what the fuel pressure is after starting the car. It is possible for fuel pressure to drop after the car starts...but highly unlikely.

I would put a fuel pressure gauge on it, and a spark tester (bought or home made) and start the car. I'd be watching for fuel pressure and spark when it dies...one of them will go away. Which one goes away?

whitemj1948

Fuel pressure was verified with a gage. I did not do the work on the car, a pro mechanic friend of my sons did the work. All good things to check I will pass this along and see what turns up. Thank you all for your input.

Red 91

Delete pro mechaniic, add competent mechanic.

whitemj1948

I find it rude for someone to make comments of this nature (and you can not even spell mechanic twice in a row), we are just trying to find possible things to look for that may not be obvious, if you can not reply in a helpful manor please do not reply. I see a lot of this on this forum and find it degrading to the person posting.

Tom400CFI

I don't think that you should take offense. If you're really dealing with a "pro", he ought to be able to diagnose this lickity split w/o any help from us...AND he ought to know the answer to:
When it stops running, what's missing; spark or fuel?

Kevova

The technician involved is not the poster. He may or may not know the specifics of the unique lt1 electronics. No manuals is tough. Aftermarket engine install lots to look at. I see OP point he has someone, who works cars, willing to help his son get car running. We will have to wait and see if tech gets stuck.

Tom400CFI

Yeah...but you start w/the basics and any good tech knows that. When it stops running...what's missing. Know what I mean?

pcolt94

In addition……
If there is a Tech1 tester available and it will interface and work on the 93, then you can read the TPS. It will tell you the % the throttle is open and the voltage output of it. See if the voltage moves smoothly thru the entire range. If it looks good, the problem is elsewhere. With the Tech1 you can also look at the fuel injector pulse width which is in MS. This would tell if the ECM is responding to the TPS and the other inputs.

If it runs in idle, chances are spark is not going away for a faster RPM. (opinion).

Couple quick checks just what I can think of as only a suggestion:
Make sure vacuum line for FPR has no fuel in it and is not wet. Make sure fuel pressure does not drop when throttle is opened to insure FPR is working proper.

Unplug the speed density unit just to see if there is any improvement in the symptom.

Check the connections of the ECM. 93 ECMs are known for screw ball problems and would not take it off the list even although it was just serviced.

If you want to get technical and someone has a scope, you can monitor the injector waveform and see if the ON duty cycle get larger when the throttle is opened.(Not easy to do and sync up if the engine is quitting).

*Is there any reason to suspect that there is water in the fuel ?

dizwiz24

Rarely ever are these no start issues a 'fuel problem'.

Unless you are talking too much fuel which fouls out spark plugs.

You say a new ecm, i would be suspicious there. I would also check and make sure the o2 sensors are still working (and not commanding too much fuel).

pull a couple easy to get spark plugs from each side of the motor and let us know if they are carbon fouled from excessive rich fuel.

Lastly dont forget to rule out the Optispark !

the oem ones are unvented and known to fail (you can add a vent).

the aftermarket china ones are crap

good luck

aklim

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2. any similar territorial unit in medieval Europe, as a feudal estate.
3. the mansion of a lord with the land belonging to it.
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aklim

I'm going with fuel pressure. Check that first. Could the injectors be getting warmed up and dying?

whitemj1948

Sorry for the lack of feed back, I am not getting much from my son, as soon as I hear something you guys will be the first to know. Thanks again for the help, it is appreciated. Mike