A little car help

asilverblazer · May 1, 2006

Symptoms:

My daily driver isn't running like it is supposed to...

The symptoms...

Rough idle.

Runs rough at low rpm's under load.

Smooths out during higher rpm's and coasting.

Engine temperature makes no difference.

Fuel economy has gone to pot (from 20.5 to 15.XX)

Performance has suffered slightly.

Seems like engine runs louder (like an exhaust manifold leak, but could be my imagination).

Occured literally overnight.

No Codes.

I have replaced the plugs, wires, cap, fuel filter, as well as several cans of fuel system treatment. All to no avail.

Car is a 93 Sedan deVille 4.9 with 160K in the ticker.

Any suggestions on what to look at?

Thanks,

Andrew

ChevyTech007 · May 1, 2006

Has all the symptoms of an EGR valve held open. You need to scan it (or have it scanned) for codes.

asilverblazer · May 3, 2006

There are no codes, I have since cleaned the EGR valve and passages into the manifold with no success, or improvement. I am going to replcae the valve tonight, next I'll try the solenoid that controls the valve. Are these symptoms to anything else, such as bad fuel injector? I've heard about the fuel pressure regulator but it doesn't have fuel in the line or have trouble starting when hot.

When I am driving it light throttle at low RPM's causes the car to shake from the engine vibrating, giving it more throttle increases this until it gets to a certain higher RPM where it clears up. Low end erformace is shot, mid range is still so-so and the high end is down from what it used to be, fuel economy is still 5MPG less than normal. The sound at the tailpipe is a definate sputter.

Anymore additional suggestions? Thanks for the help so far.