I'm new to thisforum. I have a 95 4.3 Vortec cmfi w/125000 mls. 4x4. automatic transmission 4 door. Need somehelp and ideasplease!!!
Truck runs very rough. Idles rough, surges on acceleration, tach jumps/twitches aroundtown and on highway. (Every so oftenafter it has warmed up, it runs perfect.) It seems to not be firing on all six cylindersmost of the time. SES light blinks on and off, then stays on.Recent new fuel pump and strainer. New fuel filter New plugs. Previous plugs had low milage and looked very good with slight redish-brown on center insulators. New rotor cap and distributor. Wires good and less than 2 years old.I have recheckednew plugs and no unusual signs. Burning clean. .045 gap.I 've looked into air pleumn after removing manifold tuning valve and the interior is uniformly dirty. No visible fuel or smell.Checked fuel pressure. 60#s key on. 54#s engine running. Pressure with key on only, slowly drops and seems to stabilizes at about 40#s. Pulled codes PO-107, 113, 122, 300, 401, and PO1442 yesterday.Put a new IAC on. Idles and acceleratesa little better. New coil. No difference. Found crack in pcv line. Replaced and no difference.Catalitic converter rattles and makes noise. No restricted exhaust flow as far asI can tell. Last timeI dropped tank, forward turn over valve nipple broke off.I blocked off the rubber vapor return line. Rear line is ok. Openning /loosening gas cap hasn't made a difference.
Thanx Tim

 

Please, next time do not type in such a small font..

Anyway, have your codes read. The PCM is telling you something. A flashing CEL is telling you to stop and means that a potentially damaging misfire condition is being detected. This may be a result of a non-functional EGR system. If the previous owner messed with the EGR valve, I would check into that. If he 'removed the pintle', he only made things worse.

 

Thanx Kyle. I've scheduled an appointment with a local dealer for next week.
Any feedback on how a faulty ignition module or CPS affects running / engine performance? Tim

 

I would just take it to your local parts store and have them read it. It will be free and they wil give you a printout.
Like Swart said, double check the EGR valve. If you do see that in fact the pintle is removed, make a block-off plate and throw on it(this is only to be used to make sure that it is the problem). If it runs better, get a new EGR and throw it on. If it runs the same, you know that wasn't the problem and try the next thing.

 

Thanx Bill. I'll try a local parts store first. Tim

 

Update.Ran a can of cleaner through vac. hose. After smoke cleared engine ran almost perfect... for maybe 5 or 6 miles.Pulled EGR. The screen was clogged. Cleaned and reinstalled. No noticable improvement.

Tim