1999 Ram 1500 Van, 5.9L engine, with A/C
After basically two years of driving around at less than half throttle
to avoid detonation (quite severe on hills, and downright rattling
when it downshifts going up a hill), as well as attempting various
fixes to try and stop it, which included the following:
- new plugs/wires
- premium fuel for the last 2 years
- low temp thermostat
- fuel injector cleaner
- engine analysis computer last month shows NO CODES
I finally thought, "well, it's an 8 year old engine, maybe the
timing's just drifted out a bit" so I took the doghouse off to get at
the engine, scratched a fine mark on the block for the distributor
position before I started, loosened the distributor adjustment bolt a
bit, started it up, got it to operating temp, and took off down the
Once I got to an empty back road, I put the throttle down to the point
where it starts knocking quite badly, and then reached down and turned
the distributor very slowly one direction, and then another, hoping
that I would retard the spark timing to the point that it would stop.
It didn't seem to make any difference. I could turn it to the point
that the engine quit running in either direction, but the knocking was
still there under moderate power. I could only make it worse. I
couldn't find any point that seemed to lessen it or make it go away.
After maybe 30 seconds of this, I gave up and set the distributor back
to where it was before I started, on the mark I'd made before
All seemed well, I took the van on a short 15 mile trip later in the
day, driving as I had for the last two years, with very little
throttle, and the engine behaved okay.
Today, I went to drive somewhere, and when I got on the back road, the
engine started to make some very odd sounds, almost like a rock being
shaken in a steel can. Detonation was still there if I put the
throttle down. I aborted the trip and drove it home very gingerly,
hardly putting in any throttle at all.
It's got me quite worried. Then I looked up an old post I made in this
group back in 2003, where a respondent actually warned never to do the
very thing I did: (http://tinyurl.com/25e5ms )
"As the piston come up on it's compression stroke, the computer uses
some other sensor inputs (again, intake temp., engine temp., RPM, and
throttle position) to figure out when to fire off the spark plug.
Yes, even though there's a distributor, the exact timing of the spark
is controlled by the computer (so don't go messing with the position
of the distributor trying to time the engine :). This is the
electronic equivalent of the old centrifugal and vacuum advance
systems on non-electronic distributors."
Feeling a bit of a fool at the moment - what's the worst damage I
could have done, anyway? Made the timing worse, certainly.
I wonder if a new distributor cap and rotor is all it needs?