Hello, I still having trouble smoothing out the Idle on our 1990 V6.
Things that we have changed plug wires , vaccum lines , plugs and air cleaner.
Yesterday I took the car to a shop to check and see if I missed a vaccum line or something.
They Cleaned the fuel injectors, checked the Idle
Air control Valve, cleaned the throttle body etc... Car seems to run a little better but still idles a rough . They told me the Mechanic was not happy with it ethier he stated that the Exhaust Manifolds had a couple broken bolts and there was leakage taking place that was causing the sensors
to act-up?.....does that sound resonable?....
I am really lost here and would really like some advice......Thanks, Bob....P.S. the car runs great
at driving speed it is at idle speed that it acts up?........

 

you might try taking off your egr valve and cleaning it, if it is stuck open it will cause the car to idle rough and sometimes run very rich but that all depends on how far its stuck open. Just my .02

 

If your car has a "lot" of miles, and the timing chain has not yet been changed, the timing chain might be the culprit. Over time, timing chains will stretch, causing the camshaft to become randomly out of phase with the crankshaft. The constant phase shifting is what can cause a rough idle, assuming that you've covered all of your other bases (and it looks like you have).

Do a search under either my name or "KED85" for "timing chain"--I've replaced mine before, and I got a lot of help from KED85.