Engine starts, then dies

[AZNEAL311]

I tried a search but didnt find what i was looking for so i will try this. I have an 88 GT with MAF convers. Car ran find the other day I let it sit over night and now when i go to start it it turns right over then idles real rough for a few seconds and then dies. I tried cleaning the MAF with Q-tips no help. If I try to floor the gas it dies right away. If I lightly press on the gas it will keep it going for a few more second but still dies. I hear the fuel pump prime but it is like it doesnt work after that. I tried to pull codes yesterday but nothing would happen, so no help there. A friend said to check the IAC but I am not sure where that is. One more thing, when i was driving it yesterday I was playing with a 02 Cobra and a C5 vette. When I gassed it in third it bucked real bad but then picked up and didnt do it again. It never happened before and I was wondering if that has something to do with it. It also backfires when i downshift in second gear. Is that normal?

I have 88gt hatchback with edelbrock performer rpm2 upper and lower intake, BBK cold air induction,BBK 75mm throtle body, March ram air, Edelbrock performer heads, Msd dist. and 6AL ignition, Flowmaster exhaust, Hurst shorthrow shifter,MAF conversion,

 

[Snikt89GT]

I tried a search but didnt find what i was looking for so i will try this. I have an 88 GT with MAF convers. Car ran find the other day I let it sit over night and now when i go to start it it turns right over then idles real rough for a few seconds and then dies. I tried cleaning the MAF with Q-tips no help. If I try to floor the gas it dies right away. If I lightly press on the gas it will keep it going for a few more second but still dies. I hear the fuel pump prime but it is like it doesnt work after that. I tried to pull codes yesterday but nothing would happen, so no help there. A friend said to check the IAC but I am not sure where that is. One more thing, when i was driving it yesterday I was playing with a 02 Cobra and a C5 vette. When I gassed it in third it bucked real bad but then picked up and didnt do it again. It never happened before and I was wondering if that has something to do with it. It also backfires when i downshift in second gear. Is that normal?

I have 88gt hatchback with edelbrock performer rpm2 upper and lower intake, BBK cold air induction,BBK 75mm throtle body, March ram air, Edelbrock performer heads, Msd dist. and 6AL ignition, Flowmaster exhaust, Hurst shorthrow shifter,MAF conversion,

Doesn't sound like IAB/IAC to me. If it was that you could keep it running by holding the throttle open. It would just die when the throttle was closed and not idle.

Some kind of fuel issue? When's the last time you did fuel filter? Have an FP gauge?

 

[AZNEAL311]

Ive only had the car for about a month and a half or so. Havnt changed it yet was waiting till i fixed some of the other problems i had. From what I heard the fuel pump is first activated by the starter relay then once the car is running it switches to its own relay is that right? sound kind of odd to me but thats just what i heard. If that is right could the fuel pump relay be bad and it is only getting fuel for the first few seconds via the starter relay. Where is the fuel pump relay? What about fuel reg.?

 

[JChalfan]

Doesn't sound like IAB/IAC to me. If it was that you could keep it running by holding the throttle open. It would just die when the throttle was closed and not idle.

Some kind of fuel issue? When's the last time you did fuel filter? Have an FP gauge?

I agree it's not an IAC issue. You could still rev it fine if it was.

It sounds like the problem came on very suddenly, so I would not suspect the fuel filter. It would be worth checking the fuel pressure to rule it out, though I doubt that is the cause, never hurts to check.

Is it possible your timing slipped? Is your distributor loose, turnable by hand?

As far as the fuel pump sound goes, when you turn the key to the on position you should hear the fuel pump prime for a second or two, and then it shuts back off until the car is started. That's normal.

I just noticed you have an MSD ignition and distributor. Aftermarket ignitions seem to be known for so-so quality. Is it possible to bypass the 6AL box to rule it out as a cause?

You also mentioned the car was converted to mass air. Is it possible that some splice or connection for the conversion came loose?

Jeff

 

[Snikt89GT]

Ive only had the car for about a month and a half or so. Havnt swapped changed it yet was waiting till i fixed some of the other problems i had. From what I heard the fuel pump is first activated by the starter relay then once the car is running it switches to its own relay is that right? sound kind of odd to me but thats just what i heard. If that is right could the fuel pump relay be bad and it is only getting fuel for the first few seconds via the starter relay. Where is the fuel pump relay? What about fuel reg.?

The fuel pump relay is under the passenger seat. The fuel reg is located on the passenger side of the car on the fuel rail. Near the PCV / firewall. It's the little round silver thing with a vaccum line going to it.

 

[JChalfan]

Ive only had the car for about a month and a half or so. Havnt changed it yet was waiting till i fixed some of the other problems i had. From what I heard the fuel pump is first activated by the starter relay then once the car is running it switches to its own relay is that right? sound kind of odd to me but thats just what i heard. If that is right could the fuel pump relay be bad and it is only getting fuel for the first few seconds via the starter relay. Where is the fuel pump relay? What about fuel reg.?

Your post snuck in as I was typing mine. Like I said in my last post, when you turn the key to on, the fuel pump should come on for a second or two, and then turn off. Once you start the car, the fuel pump comes back on. While the car is running, you should be able to hear the fuel pump humming. If you can't hear it from inside the car, go around the back by the fuel tank and see if you can hear it.

Jeff

 

[AZNEAL311]

I hear the pump when i turn the key to run posistion. also I just installed the 6AL MSD less then a week ago but it has run fine till today. MY dist. is tight does not move at all. I have underdrive pullies on the car so and i cant seem to find any timming marks so im not sure what it is set at. The problem came up suddenly, worked fine yesterday when I parked it. I just noticed I a have developed a leak from the bottom of my lower intake. I checked oil and dont see any signs of water or coolant in it. I am pretty low on oil and my check oil light was on.

 

[AZNEAL311]

Blown intake gasket?

Would a blown lower intake gasket cause this problem? I noticied some coolant puddled up on the block and upon closer inspection i could see it seeping out of the lower intake, and its dripping in like 3 or 4 differant spots on the ground. But this shouldnt cause the car to not run should it?

 

[jrichker]

A vacuum leak would cause all type of driveablity problems. A vacuum gauge is the simplest way of telling if you have a vacuum leak. A stock engine with no mechanical problems will pull 16"-19" of vacuum at idle and 18"-21" of vacuum at 1000 RPM.

Make sure the MAP sensor isn't connected to vacuum. On Mass Air conversions, the MAP sensor is disconnected from the engine vacuum and vented to the atmosphere. The vacuum line that connected to the MAP sensor is plugged or capped off.


Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

 

[AZNEAL311]

I let the car sit over night and it now starts and stays running, however the idle is around 600-900rpm, my car does have a cam in it however i am not sure what kind it has. I have also noticed a knocking when the motor is revved up.

 

[jrichker]

See "Help me create the Surging Idle Checklist" at http://forums.stangnet.com/showthread.php?t=534062
for help with your idle problems. The first post contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.

 

[AZNEAL311]

Sorry forgot

Forgot to let everyone know i fixed it a while ago. Turned out to be a bad computer. Replaced it and ran great.