Crank, No start when hot

[93notchback]

I know there are alot of threads covering this, but i have a 91 GT that cranks fine when cold, but it does have a high idle. When the car gets hot it will not start. Starter spins fine. Car has fuel and a light spark. IT has a MSD 6A box, wondering if that could be the culprit

 

[2000xp8]

Unplug the msd box and try it out, if you used the adapter harness it should only take a second.

If that's not it, I suspect the TFI module.

 

[93notchback]

Forget to mention the car has a MSD blaster coil, and someone cut the stock coil connnector off, so it will be difficult to try undo the box. The ECT was unhooked as well as both O2 sensors. Still no luck. I was gonna pull the codes out but my scan tool will not communicate with the car... When cold the car will rev to 3000 by itself, it you hit the gas several times it will idle back down. Its makin me pull my hair out. Seems to run a little better when i have the MAP unplugged.

 

[2000xp8]

For the high idle, that's probably the tps or iac.

Msd coils are unreliable at best, i know multiple people that have had issues with then right out of the box.

The problems you are having are a PITA, but in the big scheme of things they are small potato's.
Nothing there that costs any substantial money to fix.

 

[liljoe07]

Put the scanner away.

Use a test light. Go from the STO to the positive side of the starter relay. Then use a jumper wire from the STI to a good ground. Then run the Key on Engine off codes. See what happens.

View attachment 237213

 

[Haus]

When it gets hot again and doesnt start try flooring/pumping the gas pedal while your cranking it and see if you can get it to start.

When I had that problem, that is the only thing I could do to get it to start.

Ended up being my ECT was bad.

Good Luck

 

[93notchback]

Check engine light doesn't work so i can't count the flashes. I tried holding the pedal to the floor, still wont start. I am leaning more and more toward the MSD box or the MSD coil. the spark im getting at the plug is a real weak spark, not a strong blue spark

 

[liljoe07]

Thats why I mentioned the test light, so you dont have count the Check Engine Light.