1989 4.3l 135,000 miles...

replaced dist.cap, rotor button, plugs, plug lines, coil, fuel filter

truck starts up idles real good for about a 3min then kills it self out.. i thought the CAT was plugged so chopped exhaust it was shot anyhow.. new exhaust to come.. still didnt fix..

any suggestions???

also when you drive down the road it runs bad at low rpms if you run it hard in 1st or 2nd gear with the rpms up runs alot better..... help me out

 

Sounds like it might be a fuel pressure problem...I'd check to see what the pumps putting out.

 

A vacuum leak can cause it to run poorly at low RPM. Check the throttle body base gasket for leaks.

 

will check.. would a bad EGR valve show this kind of prob.. thanks..

 

checked for leak under the TB none found... took off EGR and cleaned still running like crap... what would a bad ICM module do would it do something like this... its not showing any codes and check engine light not on but everytime i mess with it i unplug the battery so it wont go dead............. any help.............. kind of smells like it is running rich.....