Wrecked82

All of a sudden, started missing. Could hold speed, but could not pick up speed. Afraid I was going to die on the freeway. Made it off and partway home but had to stop at a light. Took forever to get it started. Missing like an SOB. Afraid if I had to stop at a light again, I was a gonner, but managed to get to my favorite repair shop. Advised later the computer was at fault. Driver side tbi not being managed or something like that. New computer needed. Will get back probably Monday, maybe Tuesday. Good shop. Quality rating in the larger southwest side of Houston - Colony Auto, if anyone lives in Houston/Sugar Land/Missouri City.

derekderek

That CFI is a pretty good setup. ECU is only 36 years old! Might still be under warranty! Keep the old ecu. Many issues can be Googled and fixed with replacement capacitors or such.

Buccaneer

Was it going into limp mode and CEL flashing?

sambrand

like buccaneer asked about the cel light is important, cpu will very very rarely just fail like that. one thing that comes to mind is the ignition module, these are common to fail in high heat situations and would give every symptom you listed.

ctmccloskey

The "computer is at fault" is a excuse used too often by people that don't understand complex Corvettes and their issues. If the shop has not worked on the Crossfire engines this may not be a good time to start.

What you described sounds just like what sambrand mentioned above, I would put my money on the ignition module. Newer cars might have the ECU do the ignition controls but on the older Corvettes the symptoms sound just like an Ignition module going out. I would also check the coil while there but most likely the little Ignition controller is going to be the culprit. If and When a ECU does go bad it displays other weird symptoms of its own. I also own a C4 and have heard some wild things that bad ECU's are capable of like activating the cooling fans and such.

Good Luck with getting your car back out there on the road! Corvettes belong on the roads!

sambrand

keep the old cpu, even if its just shelfed item, the proms in them are available for replace/upgrade but more and more im seeing wanted ads for a virgin cpu, because odds are in a faulty cpu that has the original chips its just a weak solder or broken wire and people scavange these.

Wrecked82

No flashing lights on dash. Have had an ignition coil go out in the past and when it does, car will not start. Period. Ignition coil relatively new - several years ago. This shop has worked on car for years and does work on other classic cars. Have a few gear heads there. They are honest and if it was not the ecu, they will tell me. We shall see. Will keep this post advised what is happening. ECU was a replacement that I changed out maybe 6 years ago when I could not get rid of a code 42 no matter what. Changed out to a Cardone reman and code went away. Have WinAldl software and cable. But did not make it home to make use if it.

sambrand

aye the coil is a thing above the module, theres another piece, and it must be installed using heat sink grease right in the bas of the dizzy this is the ignition module, not to be confused with the coil.

https://www.corvettemods.com/C3-Corv...BoCbJ4QAvD_BwE

DaveL82

Replace the module and rotor. You will probably see rust like dust under the rotor where the rotor is allowing the coil to spark through also hitting the module. Module can fail per your symptoms or they are fine when cold then fail when engine heat gets to the distributor housing.

Wrecked82

Guess I was not exactly clear. Module is new. Coil is new also. New meaning in last few years. My experience is module goes out all at once. Had it happen twice in 25 years. Had inspected distributor terminals inside when putting new coil on. All clean. Have not heard from shop yet. Will stop there on way home at lunch.

Wrecked82

Partial information - ECU stuck in open loop and driver side injector not receiving a signal from ECU. Injectors test OK, which they should as I replaced then about 6 or 7 years ago.

Wrecked82

Got word car if fixed and running well with new computer. Can't wait to get it home tomorrow and if TBI's are still balanced. Longer post for another thread, but for a long time now, have now been able to get a vacuum reading on the driver tbi. Passenger side set at required 6" water vacuum, idle set properly at 550, tps set at .525. But cannot get a vacuum reading on driver side. No air leaks. Vacuum port not plugged. We shall see. Problem with driver side tbi may be reason that cannot get more than 15 mpg. Period.

Wrecked82

Finally got the car back today. 6 days - 2 weekend days that shop does not work. Got the diagnostic notes from tech. Basically, as mostly said above, the driver side injector was not receiving a signal from ecm, so was not firing. Injector and wiring tested out OK as I expected it would as I replaced them about 5 years ago. New wiring also. No codes being thrown for something like that. Apparently part of ECM malfunctioning. Shop replaced the ECM three times, each one threw off a code 42 which means a defective ECM. Poor shop. Last one, took 2 days to get from supplier, is fine. No codes now or anything. Glad I did not try to solve this, as I would have given up when the first ecm failed.

I expect a few comments about all this, so have at it.

Wrecked82

Car is driving better than it has in years. Think whatever electronic components in the ecm that relate with the driver side injector was going bad for some time. My thinking is also, no matter how well I set the tps to spec, which I do, if there was poor communication to the injector, that setting was being distorted. Going to go back through the balancing of the tbi's again. Know the process puts the ecm in by-pass, but still wonder if it was affecting the ability to get the tbi's balanced and tps set correctly. Comments please.