The truck is a 98 4x4 supercab with 70k miles.

It had a top end rebuild with new valves. Both exhaust manifolds are new and it has a new muffler on the truck.
The air filter is new, spark plugs are recent.

The truck sat for 8 months before it was bought by me and fixed. I have run 2 tanks of fuel through the truck and I am getting 13.7mpg.
I have been running lucas fuel injector cleaner in the tank to try and work things out but my next attack was going to be to put a new fuel filter on the truck.

My shop suggested to replace the cats as they may be clogged and putting on new ones could fix the lean running.

any thoughts on what could be going on? is there a vacuum line diagram for the 4.6L truck?

 

I just went out to unplug the MAF and run it without using it and it seems to run without pinging !

I will try some interstate driving with it disconnected and see if it does the same thing.

It would be great if this could be fixed by cleaning the MAF

 

If you do end up replacing the MAF, I would recommend skipping the aftermarket, and getting a Motorcraft MAF from RockAuto Auto Parts. I've had problems with aftermarket MAFs.

 

well, when I got up to speed the pinging was still there after driving 40 miles with the MAF unplugged I had 2 codes related to the MAF but none that said the truck was running lean.
I plugged the MAF back in and the normal running lean codes came back. this time I had two that said bank one.

 

Running without the Mass Air meter could make it leaner because the airflow is no longer being measured.
An area that could cause a lean condition is the EGR system.
If there is a leak thru the EGR, the OX sensors detect this and advance the timing 'AND' cut fuel back as part of a normal acton.
When not intended by a fault or commanded by the PCM, it results in abnormal drivability.
There can be your source of pinging and leaness.
The codes tells you the PCM has shifted the fuel tables all the way to the 'rich' end trying to correct for a lean condition.
Code can be missunderstood unless you know what conditions they can be a results of.
The OX sensors being at the end of the whole action is the only way the PCM has of knowing something is wrong and reports it via codes that are the results of tables being shifted out of limits.
Servicing becomes a matter of looking at the big picture.
Always be receptive of more then one problem at the same time if it seems not to make sense.
Good luck.

 

Could clogged EGR ports or bad DPFE cause this?

Judd, you don't by chance have a P0401 code.

 

I will read the code and post back in an hour.

 

P0171 System too lean bank 1

I had that stored in there twice.

I put a tank of 93 in there again. the pinging seems to be to a lesser degree although I still get it at high load / high rpm situations.

 

It was aked if a clogged EGR port would be the cause!
Well no because as discribed, the exhaust flow into the intake (no clog) results in a very lean mixture.
This being the case, the resultant mixture becomes very lean and requires the ignition to be advanced so the same point of max combustion pressure
occurs at the same point after top dead center on the combustion stroke.
Why? because the flame front speed slows down in a lean mix.
In this case, Ford also shuts down the fuel injection amount making the mixture even leaner ( this is a fuel saving intent).
If both these actions (advanced ign and richer fuel) occurr, the combustion pressures are much higher resulting in "ringing" the crankshaft, pistons and block you hear as "pinging or spark knock" if severe enough.
Why? The ignition begins combustion too early on a richer mix such that the max cylinder pressure occurs too near top dead center where the crank , rod and piston are nearly aligned and cannot move in reaction to combustion (only the inertia of the crank rotation) so you hear the pressure waves as ping or knock.
If bad enough or long enough it breaks things and blows head gaskets etc.
Good luck.

 

I'm going to have to disagree with several things here. A leak in the EGR, if it allows outside air in, will cause a lean condition, but you have to understand, that rich or lean is not a ratio of fuel to air, but more specifically fuel to oxygen. If the leak drawns in outside air, which is rich in oxygen, then the mixture will become lean. If the leak draws in exhaust, exhaust is largely depleted of oxygen, so it has little effect on the mixture in terms of rich or lean.

Bluegrass, you stated that a lean mixture burns more slowly, this is false, in fact lean mixtures burn very hot, and very fast. Running rich is a strategy to reduce combustion temperatures and prevent pinging, though the carbon deposits that are formed could contribute to pinging my elevating compression and temperatures over time.

I'm sorry Bluegrass, but your explanation is 100% opposite of reality.

 

The EGR valve was removed and tested to be working. after reinstall I removed the vacuum line on the top and plugged it with a screw. I got the same P0171 error and pinging. The last few times it has just said it was on Bank 1.
I was going to remove the vacuum line that goes on the fuel pressure regulator next and plug it to see it that changes the pinging.

 

Khan, I appreciate you position.
I think you are missunderstanding the peticular system operation which is what I am addressing.
There are indeed other senarios that fit your position, but not to this application.
Here is the FORD design parameter.
1. As soon as the EGR is called to operate, the ignition timing advances for a reason.
2. At the same time the fuel injection is reduced again for a reason.
..That reason is that extra fuel under these conditions has not enough air to support any extra/more combustion and would indeed be very rich.
..The results of this action of reducing fuel (when it is not needed is a means to improve fuel mileage) and contamination of the air/fuel that does exists causes leaness as high as 20 to 1 plus.
..Since the exhaust gas in the chamber cannot burn a second time it causes a slowed ignition and flame speed (in this peticular intended application).
..Why is due to the space the exhust gas takes up within the mixture and does not support flame travel but impedes it thus slowing combustion.
..This condition needs to have the ignition advanced to have the resulting combustion cycle be concluded at near the same piston position after top dead center so there is no driveability reaction sensed by the driver.
..Reference Ford operation doc on this system in depth and you will find the same overall explanation.
..To prove ignition advance, hook up a timing light to cylinder 1 and look at some reference point at the front of the crank for a change in position.
..Most motors actually have a timing mark at the crank but is not normally used for trouble shooting except for removing the link plug to the PCM to check to see the PCM recognizes the plug and ability of timing to be controlled.
..Use a hand pump to open the EGR just enough to let the engine react and you will see the timing advance.
..Another way if one has a monitor is to look at the ignition timing as you drive. At the point the EGR opens you can see the timing advance.
..If you apply more throttle the timing will retard. Now that is on these FORD , motors and is not always applicable to other control systems unless they do there EGR in the same manner then all the same actions 'can' apply.
..Further, this EGR action lowers combustion temperatures that is the main goal of the system as a means of reducing nitrogen oxide emmissions as mandated by federal EPA rules.
Ford system of diagnostics is very tight to within about 2% and makes Ford parts use almost manditory to work within the narrow limits that other after market part often are not made to do well enough.
.
..Back to your position; you are correct as long as it is air/oxy that is the leak.
..This changes the whole reaction to A/F ratio and the way it is handled.
..By all means a lean (excess of air) in a motor will speed combustion and have need of reduced ignition timing (retard). A condition as this overheats the cylinder and if taken to far or to long burns holes in pistons and can do all sort of damage from an ever progressing chain of events once it starts.
..I have had that experience with a race engine running straight Meth Alky and running lean for just a few second at high rpm. Holes in expensive race grade pistons.
..Last note on the Ford systems is the coils on a COP motor must have spare spark voltage available to fire the lean mix when EGR is called to operate or you get the often feel of missfire at road speeds above 45 mph with light throttle in OD. A sure sign of a bad coil on one or more cylinders that most often does not set a code because as soon as throttle conditions change to force EGR closing the miss goes away because it is not considered a 'HARD" fault by the PCM.
..So the EGR operation can show up a fault in the ignition system that many do not relate it to..
Look at this as a whole intended operation and not just in part or misunderstanding can creep in.
Good luck.

 

What you were addressing then is incorrect terminology.

I think it is safe to say, that the EGR is not part of this guys problem. You need access to a scan tool to look at live data. Codes are only a small part of the story, and pinging is still most often caused by a lean condition.

What is your fuel pressure, including under operation when the pinging is happening. Have you changed all the filters? A weak fuel pump or plugged filter can cause pinging under load.

Run some Seafoam through your intake. Carbon deposits can form, resulting in an increased compression ratio, and carbon is an insulator and can trap heat. This is known to cause issues on some engines. Some of the OHV 4.0Ls had a Ford TSB on the subject because it was common on that engine, but any engine can develop carbon deposits. The 4.0L had an octane plug, which was often removed in an attempt to cure pinging problems due to carbon deposits (the fix was temporary of course.)

Is it pinging on all cylinders, or just some? A single partially plugged injector can cause one cylinder to ping. If the same injector is dumping fuel, the computer may lean out the entire bank, resulting in one rich cylinder and three lean, which would cause three to ping.

 

I do need to measure the fuel pressure. I have not changed the fuel filter yet but I plan on doing it.
I can get a scan tool to look at live data. I own the Actron that only does engine off data at this point.
The head was removed on the drivers side with new valves and gaskets installed. that side has no carbon build up for sure.

I have been getting Bank 1 running lean for the last week and have not seen a bank 2 error but once 1.5 weeks ago.

it feels like I have very low power when accelerating.

I ran lucas fuel injector cleaner through the truck but it was pinging extra bad when I was using it.

 

Fuel pressure is in spec.
Running with a live scan tool in the truck on the way to work I got 16 misfires on each of three cylinders. (5,6&8)

The misfires came right away and I had no more even when I drove on the interstate with the engine pinging like crazy.

When I reached the parking lot and slowed to idle I started getting some more.
Cylinder #5 has some issues as the counts jumped to 144 for misfires.
Cylinder #6 had 32 misfires
Cylinder #8 had 80 misfires.

I have run this twice and I have never seen an issue on cylinder #7. If it was a clogged cat I would think it would show up on that entire bank. (the code I was getting was P0171 Bank 1 too lean) is 5-8 bank 1?