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I just got a 91 LX 5.0 with 150,000 miles. It runs very rich and rough. It idles anywhere from 1200 to 2400, unless the clutch is pressed in...then the idle drops to 1000. Continues to run rough if accel is pressed and car has very little power.

The CEL is always on. If a code reader is plugged in or the scanner plug is "jumped", one click is heard (like the fuel pump priming), then nothing happens. This occurs with both key on, engine on or key on, engine off. I get no code flashes from the cel and the code reader can't sense any activity when it's plugged in....it reads it is not connected.

The exhaust has been replaced with an offroad pipe and the O2 sensors most likely are bad, but I should get a code if that is all that's wrong.

Is this possibly a bad ECM?

Thanks for your help.
Jeff
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<font size=-1>[ This Message was edited by: webgoobies on 3/19/06 10:13am ]</font>

<font size=-1>[ This Message was edited by: webgoobies on 3/19/06 4:43pm ]</font>
 

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Start looking for cut wires around the scanner plug. I had no codes too on a car until I found a cut wire, then fixed it. Is it possible that someone swapped out a wire harness and didn't get something plugged back in (O2 sensors)? Also make sure the MAF is plugged in and EGR is plugged in. Also check the PVC hose on the back of the lower intake manifold and make sure that is seated properly. Check other vacuum connections and wire plugs. If it runs at all, the ecm should be ok unless you suspect someone has changed the programming or put a chip in it. The only other way I know of to check the ecm is to swap it out for a known-good unit ( I have done that).
 
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