Sounds like a timing chain rattle during acceleration under load, but not sure..

[YotaJunky]

I've got what sounds like a timing chain rattle during acceleration under load. It's very pronounced going up hills. I know the u-joints are good for both front and rear drive shafts and the CV joints are fine. I know that because I removed the rear driveshaft, locked the front hubs and drove it in 4WD. I also unlocked the hubs, and drove it in 2WD, with the rear driveshaft installed.

Also, when the tranny is in neutral and I play around with the throttle (reving it up quickly to simulate loading) I can't reproduce the rattling. In other words, I can't seem to reproduce the "timing-chain" like rattling sound during idle.

Any ideas? What else could it be other than the timing chain?

Troy

[amgraham]

Could be pinging.. If it just started you may have got a bad tank of gas. Usually the timing chain makes the most racket at idle but you never know. You could pop the valve cover off and check the timing chain guides to eliminate that possibility.

[YotaJunky]

The guides should be fine. I did a timing chain replacement with a driver's side steel backed guide from engbldr about 6 months ago. I've been adding methyl hydrate to my gas for the last 5 tanks. Having said that, I intend to drop my oil pan and seal up the timing cover again because I've got a small leak from both the cover and the oil pan.

What is pinging? Is it carbon buildup that ignites too early during the power stroke? What should I do if it is pinging?

Troy

[RustBucket]

Pinging is when the air/fuel in your combustion chamber ignites at the wrong time, due to screwed up timing (usually too much BTDC), crappy gas, or the engine running too hot. It's an uncontrolled combustion that is very bad for your engine.

check your timing as a start, make sure it's not too advanced. Also when you're on those hills try not to lug the engine, as that can cause pinging as well.

[22REKid]

x3 on pinging. Sounds like timing chain slop but it is preignition. I agree with checking the timing. Pinging is really bad for the engine and if it goes on long enough will burn holes on the pistons. If the timing is fine, run a higher octane fuel.

[YotaJunky]

I'll check the timing again. I do know that when I ran the truck through emissions testing a few months ago, the HC (hyrocarbon) count was very low. In fact, it was almost negligible. Is this consistent with pinging?

Also, is it possible that my timing chain could have skipped a tooth?

Troy

[YotaJunky]

I didn't have a timing gun with me, but I was able to slightly retard the timing, and indeed, the pinging is now GONE.

Thanks guys,

Troy

[mike_d]

yeah, as the weather gets warmer, more people will start to notice this. it is indeed pinging. i just run one step higher octane in the summer, that takes care of the pinging for me.