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Like a fool, I tried to turn the distributor on a '99 360 to stop pinging

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 road.

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 loosening it.

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:

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"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?

Reply to
Roy Batty
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I thought that writing looked a bit familiar :)

Probably no real damage. I'd pull the plugs, and make sure you didn't blow one apart with the detonation. I'd re-do the plug wire routing according to the TSB published on that (check dodgeram.org for it - if you can't find it, yell).

I'd also suspect the intake plenum gasket as the most likely cause of your pinging problem. Again, this has been written about many times - you should be able to pull up pages and pages of info. on it with a quick search - but in a nutshell, the gasket between the belly pan and actual intake manifold leaks, allowing the intake to suck in engine oil, which makes it's way to the cylinders, becomes carbon deposits, which create hot spots in the combustion chamber, and cause pre-ignition. The fix is to remove the intake manifold, remove the bellypan, and apply one of several fixes, ranging from replacing the gasket with RTV, replacing the steel bellypan with an aluminum one (because it's the differential rate of expansion between the stock steel bellypan and aluminum manifold that eventually causes the stock gasket to fail), or installing a kit from Hughes Engines that also addresses the problem. Obviously, when the manifold is out, it should be cleaned thoroughly with carb/TB cleaner to get the oil out from inside it. Once re-assembled, run a couple of cans of Mopar Combustion Chamber Cleaner through the engine, to clean out the carbon deposits. Finally, put in a new set of plugs, because the CC cleaner treatment fouls the plugs pretty well.

Reply to
Tom Lawrence

That does sound like a definite possibility, as I have noticed an increase in oil consumption in the last several oil changes. But I've spotted no smoke out the tailpipe and no smell of oil burning. Maybe at a slow rate of leak this would not be detectable?

If I have knocked a plug's electrode (center or outer) off and it's rattling around in there (the sound I hear now could certainly be that) I am looking at pulling the heads off to get it, I guess. I would think it'd have gone out the exhaust port, though, if it was small enough. If the fragment's not small, however, I wonder if it could have jammed an exhaust valve open?

One other thing I have noticed when taking the rig out today, is that it is running very poorly - if you put the throttle down very much past idle, it bogs as if it's starving for fuel. I don't see how a jammed valve could do that, just in one cylinder. Some other issue, happening by coincidence?

Thanks a bunch for your clues, I have downloaded all the TSBs related to the plug wire re-route and the plenum chamber gasket - both are repairs that I should have no trouble doing myself.

You've been very helpful Tom, I will try to get less stupid as time goes on!

Reply to
Roy Batty

Yep, the distributor has very little to do with the timing. When you change the plugs try Autolite 3923. They are cheap, availible at wally world, and cured the pinging in my 5.2.

An easy check for the intake plenum gasket being bad is to see if you have a vacunm at the oil fill when the engine is runnig.

beekeep

Reply to
beekeep

Be careful when putting the two side gaskets of the intake manifold on. You can put them upside down which leads to problems later. I found out the hard way.

beekeep

Reply to
beekeep

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