I've got a 2000 F150 4.6 with 203,000 miles on it. I've started noticing over the last month or so a rattle coming from the engine. It does not happen during idle, startup, or normal acceleration. It happens when I'm maintaining speed between 30-50 or if accelerate a little harder than normal. If I'm running at highway speeds, say 70 - 75 mph, I don't hear it at all.

Could this just be a valve or something sticking from carbon build up or something like it? Is it recommended to run some sort of cleaner through first before I take her to the dealer?

Thanks for any help.


T

 

Before you do anything, run the fuel down to almost empty and fill it up with the highest octane gas you can buy. If the noise stops, then carbon buildup is a pretty good guess. The best way to take care of it is go get a cleaning with a "MotorVac" or a "BG" machine.

You should also make sure all your spark plugs are tight. These engines have a tendency for the plugs to work loose.

 

Drive to a smooth piece of road. Get your truck up to 65mph and coast down to 30mph without touching the brake or the gas pedal. This will give your PCM a "baseline" to determine missfires from. If you have never done this, the PCM will have a hard time diagnosing missfires. Many people drive for years without establishing a proper baseline.

Have you changed your spark plugs lately? Try re-gappin or replacing your spark plugs if they have a lot of miles on them. If that doesn't work, go thrash on your truck a little, do some WOT runs up to 80 MPH. If that doesn't help, remove the batt cables for a few minutes then replace them. Be sure to do a "non braking" deceleration from 65mph to 30mph to reset the "baseline" again if you do decide to remove the batt cables cause the KAM will forget it.

I can't remember what the "baseline" is called. (it's proper name) But you get the drift.

 

Chester, we aren't looking for misfires here. We are trying to determine if the noise is spark knock or not.

 

Another possibility could be a misplaced wrench, socket etc. in the valley of your engine. I am not suggesting that the lost tool could be making the noise. But I have seen this happen and the loose tool rattles around enough to give a false reading to the knock sensor. This in turn will can allow the PCM to change fuel ratios to compensate for the phantom spark knock and actually generate real spark knock. Just a long shot but it happens. Try what the guys above are suggesting first as it is good advice in regards to spark knock. Good luck.

 

The procedure I detailed would help the PCM diagnose a problem related to a specific cylinder. (worn spark plug, sticking injector etc.) Spark knock or otherwise.

 

Thanks for the suggestions. I filled her up with premium for starters and will see what that does. Good suggestion Dyno, but I know there are no tools down in the valley.

I'll see in a few days when i refuel if the premium helped.

 

with that many miles on it, it could be a LOT of things. I am leaning to worn parts like maybe a collapsed lifter. Low oil pressure could cause that. At a steady speed, over a few miles, the oil could be collecting at the top of the engine, not draining back to the oil pan, causing oil starvation.... you get my point, it could be MANY things. BTW.. premium won't do a thing to clean your engine. It has no more detergents in it than any other fuel if you use a high quality gas. Do the usual. compression test, oil pressure test. look for vacuume leaks.

 

With over 200K I'd run a can two of BG 44 through it. If that doesn't help with the pinging, I'll bet the EGR valve and its passage ways are completely plugged. Those will need to be cleaned, not replaced, just cleaned. Because there are so many things that can cause pinging I'd start with those two and come back here if those things don't work.

 

All my suggestion for premium fuel was to tell if it is in fact spark knock. If it is, premium should stop or reduce it and you need to take the steps needed to fix it - combustion chamber cleaning, EGR reaming, whatever. If not, then you need to look at other things such as collapsed lifters, etc.

 

GLC is just talkin about using the premium fuel's octane rating as a "diagonstic tool". It will eliminate "spark knock" sound and help him diagnose his problem. If it still knocks with premium, then it's probably not spark knock at all, and he needs to start looking for a mechanical failure of some kind.

 

Right - thank you. It's a "tool" that shouldn't cost you much more than 5 bucks. You are going to burn gas anyway.

 

Or you can dump 5 or 7 gallons of e-85 in the tank. It's essentially injector cleaner anyway. Cheap.

 

I wouldn't dump that much E85 in on anything less than 1/2 tank of gas. That's a good suggestion - it will sure raise the octane. If you put too much E85 in without mods, it will trip a CEL.

 

well after running premium in in the tank for four days, I have yet to hear anything coming from the engine. I've tried to reproduce what I was hearing before, but it hasn't come back.

So maybe it is spark knock? But from what i understand of that, it usually happens when accelerating or when the engine is under load. Mine does it when not under much load and not at all when accelerating.

I replaced the EGR valve two years ago when I got the truck. Could it still be the problem?