Have a 93 with about 170k on it my son has been driving for the last year. Runs good but has always had more of a rough idle than we thought it should. Advancing the timing seems to smooth it out a lot.

Long story short LP died, and power was down after a new pump. A rebuilt VE and we ended up with a dead cylinder, the clatter, and a miss in the video. Changed HG, all the cylinders looked good, nothing that would point to damage. Valves water tested tight.

Still the same dead cylinder in #3 and now the clatter is getting worse. Pulled injectors and pump to another engine and they run like a top with no problems. Checked pushrods, vlaves springs, lash, etc. NOTHING that stands out as problem.

Sooo, thinking possibly a bad lobe on the cam, a bad tappet, partially sheared crank key, or ??? Sounds like a bad cam lobe and a collapsed lifter on a gasser.

Compression tester on the way to rule out valves, springs, rings, etc.

Any more ideas?

Muddy, you and Harold have driven more of these things than most of us have seen?


Thanks

Alan


http://s484.photobucket.com/albums/rr210/cerberusiam/AudioClips/?action=view&current=Idle_93.flv

hmmmmmmmmm..........

i'll point harold to this when he returns for his opinion.

hopefully someone will post a cure for this, or at least an educated guess.

NOT ME...SORRY

Have you measured lift heighth of each valve? If not, get a dial indicator and measure how far each rocker travels, that is a direct indication of cam lift.

If the dead cylinder has considerably less lift than the rest, then that will tell you that the cam is rounded.

Good advise Lumpdog.

I did not even think of that.

Yup, thats in process along with a compression test.

Talked to another forum member that had an issue with a cam in a 1993. Guess there were a few cams that made it thru the process with inadequate surfacing and treating of the lobes. We may have found one of those.