jmath

Have been chasing the problem for months.... Backfires on decel, idles rough sometimes, but when I am on it it runs great. It almost feels like it jumps time. Now it will not start or stay running unless my foot is on the gas?--New cap, rotor, wires, plugs, fuel injector service, new cat, had it timed up, had the fuel pressure checked, It's driving me nuts
Any thoughts?

RandyJ75

My car did the same thing, it was the fuel injectors. I replaced them w/ a set of the new Accel's, and now it runs great. '89 to '91's come w/ Multitechs, which always seem to fail. Also, if you can get it scanned, check out what your Coolant Temp Sensor is doing, it acts like a choke on a carb, it could be giving the ECM bad info. Mine was reading -35 degrees on a 70 degree day. My car would run very rich, and would not restart when hot.

Good luck

Sam Lam

Tell us more about the service on your fuel injectors. Were they removed from the car or cleaned on the car with injector cleaner? Any other checks made on the injectors?

Any codes stored in the ECM?

Bob

jmath

Thanks for the responses. I had a local shop do all the work indicated in the original post. Local Corvette club president recommended him. To my knowledge, he flushed the fuel injection system at high pressure to clean the system? No codes to speak of, Every once in while I get the service engine light, but it goes off when I shut off the car. The shop said they did not find any codes when they scanned it. Last night I tried again to drive the car. Would not idle, Drove it any way and as it warmed up, it started to idle barely at about 400rpm. Finally after the drive it started to behave and idle. What about the coolant sensor? If it was messed up could that cause the irractic idle and back firing on decel? last night it was about 40 degrees when I started to drive the car

woodstock

@400 rpm and below the idle is controlled by the ignition module.
Seems the ECM is backing out to do it's job. The fact that you get a SES light but no stored codes would back up that idea.
If you don't have anyone to swap ECMs with, shoot me a PM.

Sam Lam

jmath: Your car has Multec injectors which have a high failure rate. The injector cleaning that was done probably accelerated the failure of your injector coils. There is an easy test to verify that you do/do not have injector shorted coils. Shorted injector coils do not create a code in the ECM! Do this test before you start removing parts. Remove each injector connector and measure the resistance of the injector. Write the number on paper. Do this with a cold and hot engine. Cold spec for resistance is 16.5 +/-.3 ohms. Good injectors will have readings that are very close to each other. Hot readings should also be very close to each other, but higher than cold readings as resistance is a function of temp. I think you will be surprised on your resistance readings as shorted injector coils have lower resistance readings. Let us know what you find.

NOTE: Please complete your profile when you have time as this is helpful to forum members who do not know you.

jmath

Sam Lam, thanks for the info. A buddy of mine has a meter, will try to test them this weekend. I will let you know what I find. Again thank you! Woodstock, thanks for the post. Going to check the fuel injectors this weekend. I'll get back with you on the ECM. Thanks for your help

Jim