99 5.4, 75,500 MILES- CLATTERS GOING UP HILLS,FROM STOPS, WITH NO LOAD. REPLACED FUEL FILTER, CLEANED THROTTLE BODY, CLEANED FUEL INJECTORS ( I HAVE 3M KIT WHICH CONNECTS DIRECTLY TO FUEL RAIL), 3 CANS SEAFOAM. CHECK ENGINE LIGHT HAS NOT CAME ON. WILL COMPUTER SHOW A CODE IF CHECK ENGINE LIGHT HAS NOT CAME ON. ORIGINAL SPARK PLUGS. ANY SUGGESTIONS ?

 

could be a bad tank of gas. If the clattering noise starts around 20 MPH and sticks with you as you accelerate, it could be the gas.

 

BUMP

 

I know this is an obvious and most likely dumb question to ask, but is your oil level correct?

 

Have you determined if the problem is pre-ignition (knocking/pinging) or if it is mechanical (rod bearings or wrist pins, etc)?

The computer will only show what it has detected (or failed to detect when it should have). The only way to know is to see if there are any pending or stored codes by reading them. It is always possible for diagnostic codes to have been set without turning on the CEL. BTW, does your CEL work for 1-2 seconds when you first turn the ignition switch to on?

If pre-ignition, have you tried running a higher octane gas help to reduce the noise?

My suspicion leans towards those orignal plugs as a place to start. Also, check the EGR valve to make sure it isn't stuck partially open. A new (OEM only) PCV valve and a careful inspection of he PCV hose is suggested.

Clean your MAF.


Steve

PS. Unlock your CAPS LOCK key.

 

I had the same problem and it was a bad plug wire on cylinder #6 that was intermittent. Dealer replaced plug wire and runs like a top now. Not sure if thats your problem , but it fixed mine.