This past week I've noticed a slight knocking coming from the engine. It seems to only occur under acceleration. I use the cruise control pretty frequently since I live in a rural area with long stretches of 2-lane highway. I even hear knocking when on cruise control and the computer accelerates the vehicle to maintain the speed I have it set at.

I have a 2002 F-250 SD CC 5.4L with 86K miles on it. I just changed oil (at 85,700) miles. I switched from Valvoline to Mobil Clean 5000 5w/30 motor oil.

I use the same brand of gas (Shell 87 octane) all the time, so no recent changes in gas, brand or octane.

I also cleaned the air sensor inside the air filter about 10K ago, as well as cleaned out the throttle body (sticky accelerator pedal) at that same time.


I'm wondering if the EGR is going? Or, could it be lifters that need adjusting? (not sure if lifters ever need adjusting on this kind of motor or not, but it was just a thought). Any thoughts???

Thanks all,
Daryl

 

No adj needed on the lifters...Usually when the egr system isn't working up to par it will launch a code...Its pretty sensitive. Also you could have an exhaust leak near the manifolds causing a tic tic tic sound under acceleration. Maybe funkey gas?? Throw a can of octain booster in and see what happens, that may give you a direction to go.

Dick

 

Thanks, Dick. I'll try the exhaust manifold thing first, since some time back I switched back from headers to the stock manifold and have noticed this as a recurring (but not a consistent) problem. If that doesn't solve the problem, I'll try the octane booster routine. Hoping that's not the remedy, as 87 octane is expensive enough-- don't want to have to start pumping 89 octane in on a regular basis when I fill up.

Thanks again,
Daryl

 

Don't use booster with lead in it..

 

Chk your sparkplugs for being loose ! if you haven't already.
Also do a slight power brake with a helper and listen underhood (use the emergency brake also) listen to see if the noise is at the top of the engine or in the bottom end.
You could have excessive piston slap.

Rich

 

Its not pinging is it?
Prehaps try a different brand of gas.

 

No, not really a pinging so much as it resembles the knocking an engine would make when you turn off the motor and it continues to run, and knock... and knock... and knock...'til it finally shuts off entirely. Remember those days???

DS

 

Is it the engine getting real hot when this happens?

 

No, no changes in the temp gauges whatsoever. Of course, I only have the stock idiot gauges, so no telling how accurate or responsive they really are!
Why, what were you thinking it could be?
Daryl

 

It could just be a bad knock sensor sending bad info to the PCM. Cheap to fix.
Mine had a knock too, and the dealer reflashed the computer. Now there is no more knock. You might have the dealer put it on their diagnostic system and reflash it if necessary. Cost me $75.00

 

A bad knock sensor would post a code in the pcm (P0325,P0326,P0330,P0331)
After so many drive cycles it would set the MIL light on on the dash.
If you have a scan tool that can pull codes take a look.
The sensor works in the range of 0 volts to 0.5v any thing above that is a problem.

Rich

 

I wouldn't think his problem would be a bad knock sensor because the engine shouldn't be operating in an area where the sensor would come into play..The computer retards the timing when the sensor senses detonation..Most 5.4's never get to that point unless there's some crappy gas, bad egr, High temps, Carbon, mixture signaling device sending the wrong signal to the computer..

My thoughts

Dick

 

Dick I agree an disagree with you,I have had a knock sensor be faulty,meaning .
That it would read a correct voltage one time and not the next time.
The way i found it was to do a real time running with a scan tool in capture mode or freeze frame.
Also the knock sensor on a 5.4L is a bitch to change.Its under the intake mounted in the middle of the block (valley area)entire intake must come off to change it.
Therefor I'd be dam sure it was failing before changing it.

But Dick I don't think its his problem!

Rich

 

I see what yer sayin Rich... My point was if it fails the engine may ping it can't fail in the on mode usually cause its a pizeo device..The way the systems are designed they hardly get used..Its kinda like a grill starter gizmo but lower voltage it has to have action to read a voltage or on status..It actually generates a signal based on the vibration and frequency of the preignition. It can't make voltage any other way unless maybe the device is operating on a different frequency, Say normal engine operation, never seen that.

Dick

 

Interesting and informative stuff, guys. Thanks! I plan on making an appointment with Ford for the 90K major service after the first of the month, so I will bring it up to them at that time. I'll be a few thousand miles early, but it's close enough for me (and for government work, too I guess!)Meantime, the knocking seems to have stopped (again). Weird, huh?

If it turns out to be anything significant, I'll be sure and post. In the meantime, I'm hoping it was either just bad gasoline or just the EGR.

Thanks again to all for the knowledgable feedback, I appreciate it

Daryl