I have a 91 3.1 V6 with the 7730 ECU that will only run at idle and hesitates/misses under any throttle. The check engine light is on all the time and does not blink when you turn the car on. Also when grounding the ALDL pin it still stays on solid. No code 12 flash or any other signs of life. I'm thinking the ECU is fried. Any thoughts?

 

Sounds like a bad ecm .
Sent you a pm Incase you need one

 

Thanks. So what would cause the ECM to fail besides old age? I've heard some say starting with a bad battery or something like that? I'm curious so that I can better take care of the system once repaired.

 

The solder joints on some of the chips crack and become intermittent. Sounds like an engine swap/conversion. To help with longevity, the ECM needs to be both electrically and vibration isolated from the chassis.

RBob.

 

Hey folks I tried a new ECM thanks to Brian but no luck and no change in performance. Engine starts and idles fine but has a hesitation and maybe a miss under load or acceleration. Check Engine Light (CEL) is on all the time. Even with engine off and ALDL pin grounded the CEL stays on constantly and won't even blink the code 12. I guess I'll need to check all the wiring for continuity but anybody have ideas please share.

Thanks

 

Anyone have ideas?

 

I’m not sure what would cause the lack of blinking the code 12. Have you double checked pin e12 of the ecm. E12 is the diagnostic terminal that gets grounded to blink the check engine light.

 

Yes, that is the line I am grounding but the light stays on and does not blink.

 

Since the CEL doesn't blink at key-on, engine-off, the ECM isn't running from the PROM. It is in limp mode.

RBob.

 

Rbob, wouldn’t he have a code 41 or 51 ? Or does that not happen if he has a bit flip .
I think he mentioned to me he’s using a Piggyback adapter. So maybe it has a bad solder joint.

 

Depends, if the bit flip was anywhere except the power up initialize code, it would be a simple checksum error. This causes a rapidly flickering CEL and code 51.

RBob.

 

Gotcha, great information

 

Great info and thanks! I've checked all the solder joint and have reseated the chip. Same results so perhaps something is wrong with the PROM.