Please Help Wierd Noise

[MrBean972]

Hi i am new to this board but have one question.

I am hearing a noise when i hit 2,800-3,000 RPM.
Its a Rattling noise coming from the engine i assume.

The noise goes away when i shift because the RPM drops to about 2,200.

It does it most in 2nd and 3rd Gear.

Please help in any suggestions at what might be causing this.

Thanks a Bunch.

Regards,
Nick

 

[MrBean972]

PS: incase you didnt read my signature my Explorer is:

1994 Explorer XLT
V6 4.0L - 5 Speed

Has about 120,000 miles on it

 

[MrBean972]

PS: I forgot another thing.

It is also a 4x4

 

[TPLYNCH]

Hi Nick. Welcome to the site! We'll start with the simplest things first...... Check the heat shield(s) around you Catalytic Converter(s). They tend to rust and come loose and bang against the underside of the truck. If not that, are you sure it is a rattle and not a pinging sound? If your Mass Airflow Sensor (MAS) is dirty, that will cause a knocking/pinging sound when the engine is under load.

 

[mikevalora]

I am getting the same noise, I think, that you describe. The engine has to be under load for the sound to occur, typically going up a hill and the engine downshifts or "heavy" accelerating. One of the welds on my heat shield was cracked, put a hose clamp on and that did not solve the problem. Cleaned the MAF(which was clean to begin with)and the throttle body(which was also spotless). The noise does not occur all of the time and is not that loud. To be more specific, it sounds as though the "rattle" noise is coming form the left of center of the engine compartment, almost as if you would draw a line straight through the steering wheel towards the front of the vehicle. I have also tried using several cans of fuel injector cleaner, but no lck. I have spent many an hour trying to figure this one out, but no luck. It is a 93 XLT 4x4.......any suggestions.

 

[MrBean972]

Thanks for the help guys.

Another thing is when i sit in Neutral(sp?) and i rev the engine to 3,000-4,000 RPM's it doesnt make that noise.

But yes the sound is coming from the hood it seems not the tranny.

 

[MrBean972]

Yes it is a "rattle" like noise.
To me i guess a good way to describe it is a can of pennies shaking lightly.

I had a guy ride with me a listen to it and he said it sounded like a "carbon buildup".

I have used serveral bottles of Castrol Truck Fuel SYstem cleaner also thinking if it were the carbon buildup that it might help but no such luck either as mike said.

ANy clues guys?

Thanks for all the help.

 

[mrboyle]

You've got me on this one. I can't think of anything off hand that would cause the sound you are describing. Sorry

 

[Waverider]

If I am right it is spark knock. I had the same problem. If your spark plugs are fairly new, check you vacumm lines to see if the are not cracked anywhere or are not crimped. Mine was rattling real bad, and it turned out the rubber vacuum hose had rotted through. It is near the Brake booster. Your engine could also be running lean. Hope that helps.

 

[MrBean972]

Its been a long while since i changed the plugs.

Do you think that could be it.

This is an odd sound and seems to my knowledge to do it more when the engine is warm.

It also does it worse at 3,000RPM going up a hill then at 3,000RPM< going down the level highway.

I can sit and hold the engine at 3,000-4,000 RPM when its out of gear and it does nothing of this sort.

Thats what gets me.

Thanks i will check out the MAS and the Vacum tubes.

Nick

 

[mikevalora]

Nick I would have to agree with you there, in the fact that is seems to occur when going up a hill rather then on flat ground, but I have to stress that the engine has to have down shifted and that the engine must be under "load" to occur. The plugs were changed about 23,000 miles ago. What is the typical "life" of plugs?

Mike

 

[94WhiteEB]

Drives me up the wall. Like particles jumping around, my first suspicion was a leak in my air filter, but checked it w/ no avail. I've asked the people changing my oil to see if they could find a loose heat shield, still nothing. Happens to me on the highway when I accelerate usualy in overdrive. I have no clue what it is, but sure would like to find out!!!

 

[aubtc]

The description is very consistent with gas rattle. Try going up one grade of gasoline on your next fill up. If this fixes the problem then you might want to look at the ignition timing. I'm not sure if the timing is adjustable on that year. Mine is a 96 and it isn't adjustable.

 

[MrShorty]

Ignition timing has never been adjustable on Explorers.
It really sounds like what you are describing is "spark knock". The '91-'94 4.0 OHV has quite a history of spark knock.
One possible cause of spark knock is carbon buildup in the cylinders. Fuel system cleaner doesn't clean carbon from the cylinder walls. You can use a product called Seafoam to clean the carbon buildup on the cylinder walls. Water can work, too. You use it in the same way you would use the Seafoam. I suggest using Seafoam because it will have instructions and cautions with it. If done incorrectly you can hydrolock your engine and ruin it. Carbon buildup is fairly common on this engine.
Another common cause of spark knock is an engine that runs lean. Could be a vacuum leak (lower intake manifold bolts come loose creating a particularly common and unusual vacuum leak) or a dirty MAF. Again, it's fairly common. Clean the MAF, check all vacuum hoses/connections, and tighten the lower intake manifold bolts to spec.
If you can verify that the sound you are hearing is spark knock (aka detonation or pinging), these are the most common fixes (probably 90% of cases).

 

[ktown39]

I had the SAME exact symptons with my '96 Explorer and it drove me absolutely freakin' batty!!! It turned out to be a bad spark plug and once they were changed everything was great! Good luck!