94 Park Ave intermittent rough idle

Hello All,

I am new to this forum, but have read a lot on here. I have a 94 Park Ave with 70,000 miles that has a intermittent rough idle. I can not explain when or why it happens.

I have replaced the crank shaft sensor, plugs, wires, coolant temp sensors, MAF sensor, thermostat, new intake manifold and valve cover gaskets. Cleaned the PCV valve. Also have looked over the ground wires and cleaned them. looked for broken wires. Replaced a few vacuum lines.

I have had a mechanic look at it and he said it could either be the ECM or the ICM. But he is not sure that will fix it. I dont want to shell out $250 for something that might fix it.

The car will start and purr like a kitten, then for no reason after running for a few minutes or for 20 min, it will act like it is dropping a cylinder. runs very rough with no power!

I have disconnected the negative battery cable and let the computer clear, connected it again and 1 out of 2 times it will start up fine, the other, still continues to run rough. The injectors appear to be clean and debris free.

ANY IDEAS?

Welcome to AF, when this happens you must do your best to pinpoint the source, as it is missing disconnect one injector at a time when you hit the one that does not change the engine idle, this is the cylinder that is suspect. Now is it spark or a bad injector? Make sure the egr is not an issue this can also cause a problem, when not fully seated.

Thanks for your quick response. I will try disconnecting the fuel injectors one at a time tonight. I know there is spark. I have already tried that.

Also, I have already checked out the egr valve.

On a side note, the coolant fan only works when the ac is on. I will come close to overheating without the fan kicking on.

Very odd. It really doesn't matter which injector I disconnect, it still runs like it is missing. no change in the rpm and no other missing.

You my need a tach to pin the cylinder down so you can see the rpm drop.