help

[71monteme]

i have a 1994 GMC 1500, 5.7tbi. stock everything.
problem: rough/ lumpy idle. sounds like a big cam loping. feels like it would die.
also in park- i can rev the enigne up to the limiter and no engine noise. but when i put it in drive, the engine would make sound like a rocker arm was loose and tapping.

what i have done: checked for vacuum leak everywhere-none found. replace the temp sensor in the intake manifold, replaced the IAC, replaced cap and rotor, replaced spark plugs, replace o2 sensor, replaced injectors, cleaned TBI. verified the EGR is function correctly. Verified the TPS is working correctly. verified MAP is working. checked distributor shaft play-its good. checked the knock sensor and wiring-ok.

anything else i should check?

next on the list is taking the valve cover off to see if i have a valvetrain problem.

feed back is appreciated.

thanks
thanh

[71monteme]

no one?
well i took the valve covers off, the springs are ok. all valves looks to move the same distance, relashed all the valves, still same problem.

any idea? before i put it in a ditch?

thanks.

[ChevyTech]

It would be a good idea to check the computer for codes which can be done without a scan tool on a 1994.

The rough/lumpy idle, sounding like a big cam loping could be running rich, or the EGR stuck part way open.

The noise at idle could cause the spark control to retard the timing making it idle poorly.

You may want to test the compression. These trucks tend to blow head gaskets between the center cylinders as they get old. Can you hear where the tapping noise is coming from? Sometimes a worn valve guide can cause this noise.

[71monteme]

check for codes- non just the same ones over and over.
i guess the egr will be coming off and i guess we'll see.
thanks chevytech

thanh