slight knocking...

[Sphinx]

I can hear it when the engine is under load. Sounds like a rod knock but not sure. Only happens when in drive and accelerating, there is no noise when in park and I rev the engine. I cant tell if its pinging from detonation or a rod knocking. When accelerating there is a faint "diesel engine sound". any ideas? I used every grade of gas and still have the issue. I use mobil1 full syn 10w30 oil, there is only 82,000 miles on the 94 exploder xlt 4x4. Engine was never abused or raced, just a daily driver, it started doing this about 2k miles ago. would thicker oil like 20w40 or 50 quiet down a rod knock? The check engine light comes on intermittently and is giving me a cm214 code with key on engine off.

Any help would be great.

 

[pgdean]

I have the same noise coming from my '99 Eddie Bauer vehicle. Anyone have any ideas?

 

[Creager]

slight knocking while accellerating, but not while at idle and revving.

Sounds very much like detonation

My other guess would be the exhaust knocking around, but you would hear that at idle, and it would probably go away with load.

Does it repeat in perfect repeitition? If it was a rod or main bearing causing movement (knocking) it would be pretty constant. Detonation can be somewhat intermittent...

Im pretty sure if it was a rod or main rocking around, you would hear it at idle.

Carbon buildup can do a few things that would create detonation. First: Carbon over-time will build up and cause somewhat of a smoothing effect on the intake runners/walls, causing the gas to condense and drip into the cylinder as a liquid. Second: Build up around the valve seat and probably on the valve seat itself would cause seating problems and therefore you may not be getting full compression... easy detonation. Third: MASSIVE amounts of carbon build up from MASSIVE oil loss can cause mountain ranges of carbon build up on pistons, effectivly raising the compression ratio (takes a lot of oil burning, but ive done it)

Best thing to do? Have the heads and intake hot-bathed, have the valves grinded, and use a razor blade to scrape the pistons clean. All detontaion will seize after all that!

 

[MrWizard]

Reduced Octane Plug

You could try temporarily pulling the "octane adjust shorting bar".
Removing it retards the timing for using really low octane fuel.
Shouldn't have any knock then.
It's a two prong plug that attaches to a connector near the
heater core inlet hoses - under the hood near the passenger side.
If that "fixes" the problem, a more permanent solution is the seafoam
that a lot of people here seem to use for cleaning out all the carbon.

Here's a photo of the reduced octane connector with the
shorting plug removed in a 1994 explorer:

 

[schmidlkofer]

You could try temporarily pulling the "octane adjust shorting bar".
Removing it retards the timing for using really low octane fuel.
Shouldn't have any knock then.
It's a two prong plug that attaches to a connector near the
heater core inlet hoses - under the hood near the passenger side.
If that "fixes" the problem, a more permanent solution is the seafoam
that a lot of people here seem to use for cleaning out all the carbon.

Here's a photo of the reduced octane connector with the
shorting plug removed in a 1994 explorer:

little coke on the hands?

 

[Texan01]

My 95 with 206,000 miles does it too, I thought it was from running a bit too thin of oil (5w-30 mobil 1) so I switched to 10w30. i know it's not from carbon buildup as I just had to replace the head gaskets so I cleaned the heads and the pistons while I was in there.

Only thing I can think of is exhaust resonance. Even my neighbors 91 X does it. I can hear it at idle but only at the tailpipe, if I get closer to the engine it goes away.