Hi all,

I'm new to the forum and have a problem that has been stumping me for a while. The truck is a 97 F150 4.6 with 162,xxx. A while back I noticed that whenever I am accelerating under load, getting on the freeway, passing someone, etc. as I press the gas pedal the engine is making a rattling/chatter noise. It doesnt do this when parked idling. It seems to be coming from the middle of the engine somewhere and I can hear it pretty good from inside the cab. If I press the throttle more the noise gets louder and faster and I can vary the amount it does it by using more/less gas. I replaced plugs, wires, pcv, belts, fuel filter and do regular oil changes. Anyone here have this same problem or have had in the past? I am pretty knowledgable when it comes to vehicles but have never seen something like this before. Thanks for any help.
-Matt

 

Mine does it, and I have read that the solution is a reflash program for the PCM. I think its a fuel delivery problem and what you hear is valve ping. I have not found a TSB and I don't know how to read the reflash IDs on motorcraft web site. The other theory is the rocker arm retainers come loose and float on acceleration.

 

You need to clean the EGR ports on the throttle body. They get clogged over time and cause this problem. Easiest way to do this is to remove the TB and clean both ports

 

Yup!! Mine did something like that about three years ago , but I couldn't remember what I did to fix it lol..

I wasn't trying to fix that problem at the time , I just decided to clean the TB and Elbow one day and honed those ports out well.

Been smooth since then..

 

it also could be a loose bolt on your manifold. mines doing the same thing and doesnt look so good on the money side.

 

Have you tried a tank or two of premium gas to see if it's spark knock?

 

Amen. Use some octane booster or a tank of 93 Octane to test - if the engine doesn't ping when the good stuff is in the tank, you're experiencing spark knock. Perhaps time for a tuneup?

 

I have the same issue with my 97' 4.6L. When I came to Arizona from Washington state the problem became much much worse. I have used premium grade fuel and octane booster on different occassions and I did notice a considerable improvment doing that. Day to day driving and idleing my truck runs smooth and quiet its just hard acceleration the things get rough and chatter. With gas prices I have been running plus and that to seems to have helped things. Regular gas and my truck just do not get along.

 

I have a similar problem to you guys.....TB is clean, tune-up and everything. New MAF maybe? Seemed to help when I cleaned it, but back to normal after a month or so.

 

i had the same problem with mine a tick tick tick noise.when accelerating....

yesturday i was going down the highway and all of a sudden my yellow check engine lite came on and started to flash....the truck started to shake and nock real bad......i replaced the plugs and wires ......low and behold my mechanic thinks it may be a bent rod or a bad valve...im probably going to replace the engine..now to find an engine what type?.. anyone have any thoughts??? lol

 

This is where I would go for a motor - hands down. I don't trust any rebuilder as far as that goes ... I would rather have one out of salvage with low miles that came from the manufacturer - to many problems with a rebuilt modular..

http://car-part.com/

They locate a motor for you close to your zip code..