4.0 Harsh engine rattle

Reply Subscribe

Thread Tools

Search this Thread

Oct 25, 2005 | 11:32 PM

428_cobra_man

Thread Starter

Junior User

Joined: Jul 2004

Posts: 84

Likes: 0

From: Abbotsford B.C.

4.0 Harsh engine rattle

Has anyone ever experienced a Loud Crackling noise under hard-High RPM acceleration, my 92 4 liter does this when I tramp the pedal or accelerate hard to pass, it sounds almost like shaking a marble around violently in a tin can, The motor has 345,000 KM on it, runs excellent good oil pressure no ticking or anything else, I am sure it is not rod bearings, I was thinking maybe oil pump? or timing chain noise? anyway it bothers me as it sounds really harsh with the doghouse taken off, if anyone knows what it could be let me know

(I wonder if maybe it isnt piston slap?)

Oct 26, 2005 | 05:49 AM

96_4wdr

Post Fiend

Joined: Apr 2005

Posts: 5,720

Likes: 5

From: Washington state

pre ignition aka pinging...search Aero forum
usually caused by carbon build up on top of pistons and combustion chamber...can be caused by too high a heat range of spark plug...or low octane fuel
fuel mixture ignites explodes prematurely before ign spark...carbon heats up and supplies ign source.
run a couple cups of water thru vacuum line while engine hot and at 2000 rpm
or use a can of Seafoam into vacuum line...
shows up mainly on high mileage engines.
dangerous to long engine life..can crack heads...bend rods..crack pistons

Oct 27, 2005 | 02:02 AM

428_cobra_man

Thread Starter

Junior User

Joined: Jul 2004

Posts: 84

Likes: 0

From: Abbotsford B.C.

I think you are right, I will try the water thing and , Ill also put 20 bucks of High Octane gas in and see if it helps.

Oct 27, 2005 | 03:27 AM

96_4wdr

Post Fiend

Joined: Apr 2005

Posts: 5,720

Likes: 5

From: Washington state

usually high octane gas will not help with a point source buildup of carbon, like having a burning match in the combustion chamber when the engine is warm..boom
no spark plug needed

if water injection does not help...check base timing with timing light...may have failing worn cam position sensor or its drive gears

Oct 31, 2005 | 03:58 AM

428_cobra_man

Thread Starter

Junior User

Joined: Jul 2004

Posts: 84

Likes: 0

From: Abbotsford B.C.

I tryed the water thing... about 2 quarts of water through the brake booster hose.... It worked Incredibly well. the van idles smoother now and no longer pings or rattles I am very impressed. While i was accelerating hard to test it I noticed that My oil pressure drops to nothing At WOT, at idle its good... hmm something else to bug me!

Oct 31, 2005 | 04:15 AM

96_4wdr

Post Fiend

Joined: Apr 2005

Posts: 5,720

Likes: 5

From: Washington state

probably a chunk of oil breakdown crud plugging port of oil pressure sender, oil pressure goes up on WOT pressing chunk tighter into opening, replace sender

on hot engine next oil change, add to crankcase, 2 quarts of Rislone, diesel or kerosene in crankcase, run engine for 1 minute to stir with oil, shut off and let set overnite to digest crud in crankcase.

Last edited by 96_4wdr; Oct 31, 2005 at 04:18 AM.

Oct 31, 2005 | 12:18 PM

copper_90680

Postmaster

Joined: Sep 2003

Posts: 4,452

Likes: 1

From: Southern California

Quote:

Originally Posted by 96_4wdr

probably a chunk of oil breakdown crud plugging port of oil pressure sender, oil pressure goes up on WOT pressing chunk tighter into opening, replace sender

On the 4.0L, replacing that sender ranks right up there in my book with the spark plug replacement