Rough fast Idle

[SVX_commuter]

I have this problem with the engine. I have had it for a few months now. Any help would be great.

 

The idle speed is fast at 2000 rpm after it is warmed up. Turning off the engine and restarting drops it down to 800 where it is usually. The idle has gotten rougher. Gas mileage is dropped from 26 to 22.

 

I found the problem is with one cyclinder. I disconnected each injector and found that cylinder by battery had no change, the engine stayed rough with disconnect. I checked the coil with spare plug and spark looked okay.

 

I am thinking this is the fuel injector. Is there any other electric or mechanical things that can work intermitant?

 

It still runs and that is what counts.

 

John

[abog]

Fuel injectors can cause this condition . There are two types of injector failure, one is that the electrical coil in the injector will go open and the injector goes dead. The second is when the injector, or the injector oring starts to leak fuel into the cylinder. You also have to verify that the injector is receiving power to function. You can hear an injector working when the car is running, if you listen with a screwdriver or stethoscope directly on the injector it will sound like a rapid clicking sound. If you cannot hear any sound it is dead, test the resistance of the injector and verify power and ground. If ok, pull the spark plug and read it's condition, if it is dark and wet that is an indication of excess fuel. The other thing, while you are there is do a compression test.

[porcupine73]

What year and model vehicle is this? The combination of the high idle and no injection pulses on cylinder #1 is a known issue for some certain soobs, something about if the ECU believes it can no longer control the engine idle RPM it will cut fuel injection to cylinder #1.