Hello,
My G engine is mostly stock. I have a Pertronix ignition and a Mopar
Performance Cam (Which I degreed to the ORIGINAL Ram engine specs, not the
Mopar Perf specs) and lifters. Stock pushrods and rocker arms. The block was
over-bored .040 therefore it had new pistons installed. This engine was built
close to 20 years ago and I am guessing I have put around 20-30,000 miles on it
since. Otherwise, engine is stock.
Last Fall, my son and I drove the car approx 120 miles to a car show. On the
way home, it developed a miss, a cylinder or cylinders not firing. It seemed to
get worse as we continued home and the freeway.
The car was parked and only taken out of the garage once or twice for very
short drives since then. The miss seemed to be still there, but not as bad as
it was on the freeway. A few weeks ago, we got it out to take my son to his
Confirmation. On the way to church, the miss turn into a serious miss-fire. It
was violent. It rattled EVERYTHING. clearly not a miss, but cylinders not
firing when they should. I did not notice any backfiring thru exhaust or
intakes.
When replacing the spark plugs. we found #3 and #5 electrodes squashed and
therefore zero gap. There was no evidence of mechanical interference (broken
valve,piston…). Also, I have always run the car hard enough that it is
difficult for me to believe there is any carbon buildup which could’ve broken
free and caused the spark plugs being compressed. We ran a compression check
and found each of the cylinders very close and good (115-120). We also replaced
the cap and rotor. Plug wires were not replaced as I don’t have an extra set
and the wires on the car appear OK.
The car fired OK and seemed to run good, there was a very slight hint of a
miss, but otherwise seemed OK. I let it idle and get up to temp. On the test
drive, it started to miss-fire again, and again it was violent, massive
vibrations throughout the car. We brought the car home and parked it. I noticed
the front face of the intake manifold on the drives side (in front of the
master cylinder) looks to have exhaust gas residue on it. I have yet to re-fire
the car and feel for exhaust leaks, nor have we removed the spark plugs, but I
am suspecting there will be issues with #3 and #5 agains as they are positioned
close to the intake manifold where the exhaust gas residue appears. While the
car is at idle, no exhaust leak can be heard.
I'm asking for suggestions in trying to diagnose what may be happening, prior
to taking the intake and valve cover off? I’m more inclined to believe this is
a mechanical problem vs an ignition issue. Could this be wiped lobe(s) on the
cam? Could a lifter collapsed? Bent pushrod(s)? What else?
Thank you,
Richard Osborne
Columbus, OH
