I have been trying to diagnose this problem for a while, and while I haven't found the cause, I have been able to get much more detail.

I have 42,000 miles on my 03 F150 (5.4), and it has been pinging under load since about 18,000 miles. The dealership always told me that it was normal, and that having a rough idle was normal (you can put a glass of water in the cup holder, and you can see it shake like the puddles in Jurassic Park when the T-Rex was coming).

Anyhow, warranty is up, and I wouldn't take my truck back to this particular dealer to save my life. The computer still shows no problems (which is why they wouldn't do anything, I'm sure).

It pings and has rough idle even when the weather is cold. Recently I have done a lot of experimenting with octane levels of my fuel. I have noticed the following:

• If I switch from 87 to 91 octane, the pinging and rough idle go away immediately (assuming an empty tank). This continues for for a number of miles, at least 30.
• After this time period, the pinging comes back just the same, and identical rough idle.
• If I now switch back down to 87, the engine pings/knocks very badly, for about the same 30+ miles, then it settles back down.

I am thinking that there must be a sensor that is faulty, but just reporting bad values, just not out of range. Because the engine is obviously adjusting for something, just doing it badly.

It doesn't ALWAYS have a rough idle, but I haven't been able to come up for the rhyme/reason behind when it does it or when it doesn't. It almost always does the pinging under load on the highway, though. Like if I am accelerating to pass someone, especially pulling a load.

Any ideas?

Mark

 

Check, clean or replace the Plugs, plugwires, coil pack, egr, vacume hoses, pcv, iac, throttle body, o2 sensors, fuel filter....

Also check for the computer codes, I've heard that sometimes a the CEL wont light up but there could be some trouble codes. I had a 97 that would "stutter" when trying to overtake someone on the high way, and it was that the plugs weren't gapped correctly.

 

The change you see is the PCM changing it's tables in response to the octane change. The final result is always the same for ignition timing. When you change back, the tables are shifted for the 91 gas but is now to far shifted for 87 so the timing is farther advanced making the ping very pronouned.
What you have is a marginal operation that can be due to a stackup of tolerences with the sensors but they never go out of tolerence so far that the diagnostic program would detect a fault. At this point you could never know what sensor or combination might be the source.
This most likley will never change for you.
I would suggest you talk to Mike Troyer about the problem. Visit the Superchip forum.
I bet he knows how to solve it.
I have my thoughts on how to solve it but I am not in the biz of programing.
Basicly some program changes are in order that could have been made by the dealer with a reflash but getting them to do it is another matter.
I don't think you made a big enough stink about it to the dealer. I would have at least tried several dealers and gotten the area rep involved as a last effort.
Good luck.

 

Well, its been a while since this post, my truck now has 82,000 miles on it, but the problem still exists. In the meantime, I have:

• Had the throttle body professionally cleaned
• Cleaned the throttle body myself several times
• Replaced fuel filters several times
• Replaced the upstream O2 sensors
• Had the EGR valve(s) cleaned at a shop. They said that they looked just fine, and weren't the problem
• Changed air filter types several times
• Changed exhaust (not related to this problem, just happened to come into a good deal for a Magnaflow system)
• Changed the plugs

Gas mileage has continued to drop, down to around 10 mpg on the 5.4. Neither the dealer, nor a separate shop can figure it out, so I get to play with it on my own now.

So, looks like Bluegrass was dead on. Need to start looking into a programmer. I was stubborn and insisted to myself that it must be a sensor I can find and replace.

Not throwing any more parts or work at it until I can get a readout of what's actually going on with the danged sensors.

 

I hooked up an OBD-II USB adapter to my laptop and drove it down the highway about 100 miles.

What is interesting is this:

I noticed my ignition advance is ALL over the map, even at the same vehicle speed & rpm. Sometimes its 35 degrees, sometimes its 17 degrees, and sometimes its 12 degrees, and anywhere in between. If I am at like 70 mph, hit the gas, and it starts pinging, I see the timing drop down to 3-4 degrees.

I have never looked at the timing before on a vehicle, but I know on my 74 Nova, the theory is that at higher RPMs, with the vacuum advance, I have it set to around 34 degrees total advance. Its at around 16 degrees initial. What I see on my truck seems very out of whack.

I have readings from the O2 sensors as well, but don't really know how to interpret that data.

So, something is causing the timing to retard heavily. The million dollar question is what, though. Is it retarding to stop knock? Or is it retarding for some (retarded) reason and being SO far retarded is causing the pinging.

This is definitely the best time of the year to test it though, as the 5.4 seems to ping the most around 50-65 degrees F.

Mark.

 

I’ve been searching the web and have actually had a similar problem with my 03 5.4 4x4 with about 74,000 miles. This as been going on for about 14,000 miles. When I start up the truck with the engine cold, I get a pinging/clacking noise coming from under the hood. Usually when the engine has warmed up and driven a few miles this noise goes away. Again no trouble lights and usually when the engine is still at normal operational temperature, the truck starts with no noise at all (most of the time). I’ve tried several things and have searched dozens of treads on here as well as other forums. I use the recommended 5-20w motorcraft oil and filter. I also read that it could be a broken exhaust manifold bolt or something along that line, Im not sure with that. I also don’t understand why it goes away after the engine is warm. Its definitely not normal, it never made this noise when I bought it (go figure). I really have no clue where to start and I don’t think there has been a significant drop in MPG. Any help would be greatly appreciated. Could it be that the engine is having trouble delivering oil to the cylinders? HELP NEEDED

 

It could be the type of gas that you are using... see what happens if you put in 91 or 93 octane... but don't use it regularly because it will just mask the problem.

 

I'm not sure that the two are driectly related. For the rough idle, I would check vacuum hoses for cracks/leaks, replace the IAC,PCV.....

You say you changed the plugs but never the coil packs?? I'd replace all 8 and see what that does for you, if nothing else Troyer might be able to help you with a decent tune, but I'm guessing there is something mechanical as well that needs to be taken care of.

 

Don't these engines use forged pistons? One of the properties of forged pistons is that they expand more than others when heated. This means you have to build in greater tolerances, and when the engine is cold, you get piston slap. This is normal, as long as it goes away after the engine is warm. It is another reason not to go nuts on the throttle till it warms up as well.

Mark

 

IAC, PCV has been replaced multiple times since this issue began at 15k miles, it is now at 100k miles. So have fuel filters, had throttle body, EGR valves cleaned by hand.

I have not been looking forward to replacing the coil packs due to their cost. I am right now going through the process of checking their resistance on the primary and secondary sides, and so far 3 of them have checked out. I understand they can be bad, and not fail this test, but I have thrown so much money at this issue already that I'm afraid to throw another $600 or so to replace all 8 packs. Unless I should replace them at 100k anyways?

Mark

 

Yes you should replace them, and no you shouldn't pay $600. Check out global automotive on EBay. $96 for a new set to your door. Just got mine, haven't put them in yet, but it is on my list of things to do very soon. There are quite a few members on here using them and have no issues. You've also checked the vacuum lines?

 

Ordered a set of coils, as I'm not scared of them being a wasted purchase at that price. Will probably go back to the Motorcraft plugs at this time. Hopefully the coils get here promptly.

 

Mine took all of 4-5 days and that was over a weekend. You should get a tracking number so you can see where they are at. I've also read that Motocraft are really the only plugs you should use, they seem to work the best.

 

Im going to try the higher octane gas on the next trip to the pump (which shouldnt be long )



Im not a huge gear head but what you said makes sense. I definitely dont go nuts on the gas period. I usually let the truck warm up for 40 seconds depending on how long it takes to idle down and then take it easy till its up to temp, but I will take your advice and not sweat it to much.

Thanks everyone for the help, even though I kind of interupted the thead Thanks

 

Going hard on a cold motor is one of the worst things you can possibly do. Espically in sub-freezing weather when oil takes a little longer to get flowing all the way up to the valve covers.

It's kinda surprising cars don't have a method to protect against this like, limiting throttle for the first minute or something. My 4 stroke Yamaha sled limits the rev's to about 5,000(I love a 12,000RPM redline in a 4-stroke) until the thermostat opens, usually between 30-60 seconds depending on how cold it is. Then again, that motor takes 0w oil

As for the TC I'd bet a tune is the only way you'll get the pinging to stop. A reflash on the ECU could do it too, but a dealer has to do that, and they typically won't unless they deem it necessary (code for corrupted data pops up).

Tuners and the tunes to go with them aren't cheap, but they can clear up a lot of persistent problems, as well as get some pretty good performance gains.