[DanC]

'89 5.0 TPI in a FB Formula

Car ran fine to work. Trying to leave work engine would start/die, finally stayed running but ran rough. Had to "pump" accelerator to get moving w/o stalling. "Service Engine Soon" light 'on'.

Once warmed up engine ran fine but during the 45 minute drive home the Service light would cycle between on steady, flashing, or off.

Now the computer will not go into it's dianostic mode. The fans come on but the light just stays on steady. And engine is start/dieing as the night before.

I would think the start/die might be the water temp sensor (for the computer) except for the fact the computer will not go into test mode.

I disconnected the battery and waited about a minute to reset computer. Problem did not change.

Any ideas?????

Thanks,
DanC

[DanC]

'89 5.0 TPI in a FB Formula

Car ran fine to work. Trying to leave work engine would start/die, finally stayed running but ran rough. Had to "pump" accelerator to get moving w/o stalling. "Service Engine Soon" light 'on'.

Once warmed up engine ran fine but during the 45 minute drive home the Service light would cycle between on steady, flashing, or off.

Now the computer will not go into it's dianostic mode. The fans come on but the light just stays on steady. And engine is start/dieing as the night before.

I would think the start/die might be the water temp sensor (for the computer) except for the fact the computer will not go into test mode.

I disconnected the battery and waited about a minute to reset computer. Problem did not change.

Any ideas?????

Thanks,
DanC

[Ken French]

Dan, sounds like you have a bad ECM. Typical scenario when they fail. It goes into a back-up or limp home mode. If you tap on the side of the computer, while it's running, it may straighten out. In any case, it needs to be replaced. Ken

[george kujanski]

I agree. If the computer is sane, it will operate the SES light in diag. mode. If it won't operate the light, it's likely brain dead.

Had a '85 Olds once that did the same thing. Ran poorly and diags would not work, Took apart the ECM and debugged it; turned out it had a bad voltage regulator for the processor power, i.e. the computer was not working at all.

I repaired mine, but unless you are capable of that sort of thing, just replace it.

George

[DanC]

Thanks fellas, I had a feeling it was the computer due to the no diag mode operation. The good news is they are "only" $89 reman @ Advance Auto Parts. But did not want to go that route unless someone had an actual reason for suggesting that, such as Ken and George.

The other thing I noticed today is the the fans start running as soon as the ign key is turned on as if the A-B jumper is in the test connector.

Ken, I tried the tap method and the ol' aircraft avionics "re-rack" procedure to no avail.

George, you have quite a way with words there!

DanC

[DanC]

Good news and better news.......

The computer (ECU) was the problem. Changed and now running great again and the diagnostic mode is operational.

The better news is my '88 parts car had a compatible ECU, just had to swap out the PROM. That saved me $90 bucks

DanC