INaband.....How did you come to the conclusion your ecm was bad? I am batteling the same problem and havent found the fix yet.

 

.........My shop tuned my car Friday, it would idle bad dumping fuel, so it needed an ECM, and the old one had a hypertech chip, which was making the old computer inject too much gas I think, also I needed new plugs, and I.A.C. motor...now it runs fine...but the ECm was definitely bad, and a reman one is cheap, actually

 

I also had to exchange the ECM once, because it would not scan anything and the car would not start, now on my 2nd ECM in 2 days...

 

Here are my thoughts. You have old gas and the car has been sitting for quite awhile. I would put a full can of Seafoam in the tank and top the tank off with fresh gas. Drive it as much as you can. This will only cost you $8 for the Seafoam and what the gas will cost you.

It seem the more you drive it the better it gets. This is what makes me think it is gummed up injectors and old gas.

Also you asked what it would help putting Seafoam in the booster. What people are trying to say is remove the vacuum line from the booster and slowly pour the Seafoam in the vacuum line.

Hope this helps. Tim

 

Seafoam is in my tank right now, it works..

 

So how would that help pouring into the vaccuum system? I understand that it'll smoke like hell and probably help me in locating a vaccuum leak if i have one, but what else does that do? I don't understand how a carbon cleaner or what not would do anything to the vaccuum system which should only have air in it, how does it get gummed up?

 

Pouring the Seafoam in the vacuum line while the engine is running will clean the carbon from the back of the valves and in the combustion chamber.

By pouring it in the Booster vacuum line the engine will suck the cleaner in the plenum and run it through your engine and burn it.

Doing this will not help you find a vacuum leak. The only way to find a vacuum leak is to spray something at the areas that could be leaking while the engine is running. While the engine is running and you are spraying something and the engine RPM increases or the idle becomes smoother you have found your vacuum leak.

When I said your injectors are gummed up is when fuel is left setting it will varnish and become sticky. This will somewhat clog your injectors causing a poor spray pattern. If this has happen the fuel will not atomize well and the engine will run poorly at idle. As your RPMs increase the additional air flow will help atomize the fuel. This is why I think you have a rough idle and it runs better at higher RPMs.

I could be totally wrong but if I am it will cost you very little compared to some of the other suggestions.

In my opinion when trying to figure something out keep it simple and don't think the worst.

 

I do have quite a bit of knowledge about cars and know what happens when gas sits

Unfortunately, i'll probably have to bring this problem back to life in the spring as i drove the car last saturday for the last time until the spring. Thanks for all the help though. First thing i'll do when i pull it out of storage is try the seafoam thing.

 

 

Pulled the car out today to take it into for emmissions and i am happy to say that it passed. Hopefully, this means my injectors should be ok because if they were bad i'm not so sure that it would have passed. What do you guys think?

 

Have you ohmed the injectors yet? That'll answer your question pretty quickly.

 

How difficult is it to get to the injectors? What should the be reading ohmwise?

 

Any responses on what the ohm readings should be, and how difficult it is to do it?

 

Very simple, you simply unplug the injector connectors, two wires go into each connector. DON'T worry about what they're supposed to read, although my FSM for an 87 says above 10 ohms, mine read around 16. What you're really looking for is consistency, they should all read within +/- .5 ohms. You should read them both hot and cold. Doing this will give you a read on the injector coil health, next follow it up with a fuel pressure test.

 

These c4, especially earlier ones, tramline a lot on the road. Due to suspension setup and tire setup..

Also, my 140k mile corvette has NO rattles/creaks etc in it.

 

Third, not sure if this is a problem or just a trait of the steering. Car seemed to be all over the road.

How old are the tires? Just got my 85 a few months back. It was all over the road, I looked and the tires and they were 12 years old. Put new ones on, it made a world of difference, like driving a completely different car.

 

Forth, this is a thread from 2008.

 

+1 on checking the injectors, that was the problem with my 89's rough idle. They threw no codes either, it was bad coils in several so no amount of sea foam helped. DO NOT replace with 21lb Accels, you will lose considerable power.

Rick

 

Why even check them? They are old and not ethanol resistance. I'd just toss them for new rebuilt ones.