The engine is completely stock as far as I know.

The fuel pressure test was about 10-15 minutes in duration. I ran the engine hard for a good portion so it was quite warm by the end. Cold or warm, the fuel pressure was consistently 40 psi when I was on the throttle, from slight throttle to full throttle. The only time the fuel pressure dropped to 30 psi was when the throttle was closed.

I had higher octane fuel in the tank when I ran the fuel pressure test. There was some very slight pinging during the test like I normally experience when running higher octane fuel.

The fuel pressure when the pinging occurs under load is at 40 psi. For me, this eliminates fuel pressure as the likely cause of pinging. However, a longer duration test may indicate some other problem with fuel pressure.

 

Sea foam ? I would try that. Its works for me. Pour some in the fuel tank too.

 

I have the identical symptoms on my high mileage '99 V10 (see this post https://www.ford-trucks.com/forums/5...-in-a-v10.html)


Eric, why don't you go ahead and change your knock sensor so I know if I should change mine? ;-)

Seriously though, the knock sensor does make sense. I was suspecting increased compression from carbon build-up, but even if that is the case, presumably the knock sensor would kick back the timing reducing power and eliminating the pinging...

No way to get to the sensor without removing the intake manifold??

 

Since the knock sensor is a lot of work to replace what I am going to do next is unplug the sensor and see how much difference it makes. Presumably if the sensor is bad the ping won't change much with it disconnected.

Before I do that test, I am going to wait until the fuel runs low and put in regular that way I get a much stronger ping making it easier to tell a difference.

 

I found that removing the knock sensor is fairly simple if you first remove the alternator.

After unbolting the knock sensor, I left the knock sensor electrically connected and secured the knock sensor with zip ties to prevent it from touching any part of the engine. There was no difference in pinging with the knock sensor on or off the engine block. This suggests a defective knock sensor.

My next step is to replace the knock sensor.

 

Way to go after it Eric Keep us posted.

 

Eric! That's cool to know about the knock sensor!

And your fuel pressure test sounds exactly like what it should be doing.

Let us know what happens.

 

Thanks for the update Eric. Please do keep us posted. I'm having some problems with pinging as well.

 

I have been battling a ping issue. All winter it was pretty bad. My current tank of gas, the ping is gone. Did I get my first tank of summer blend fuel?

 

I wonder.

Used to be here on Long Island, the pumps had the sticker saying "this gasoline contains MTBE between the dates of XX and XX". I thought it was during the summer that they put MTBE in it to combat the smog/ozone.

Since the switch to Ethanol (MTBE was banned in NYS), the sticker just says "contains 10% Ethanol" ... I think they do it year round here (Metro NY) now.

 

I replaced the knock sensor with the identical Genuine Ford part made by Bosch. Much to my disappointment, it still consistently pings the same as before.

This suggests to me that 1) the replacement knock sensor may be defective, or 2) the knock sensor may not adequately detect the ping or 3) the signal is not processed properly by the PCM.

It appears that the next step is to find a good Ford service tech that can analyze the knock sensor signal under load. The challenge is to find a good Ford service tech.

 

Do you think you need to disconnect the battery and reset the PCM? I wonder if the computer has 'learned' various timing and fuel curves based on a bad sensor. Just a though.

Doug

 

Yeah, definitely reset the PCM... didn't even think of that ...

 

Yes the pcm should be reset.
After so many drive cylces it will also relearn. Also
Eric
Did you run with the KS disconnected also to se if a code or chk engine light would come on??
This would chk the ks sensor circuit to the pcm .
Without the need for a tech.

you may be back to square one here and need a reflash of the pcm as was stated awhile ago .there were quite a few bad programs out there .

What brand fuel are you running?
What elevation is the truck driven at most of the time?
Had you cleaned the maf ?
Also do you have access to a scanner ?
If so one with a capture mode in it ,A look at the long term fuel trims might be able to shed some light here!

My recommendations
reset pcm drive it for a couple days see what happens.
if no change ,disconnect the ks sensor see if you get a chk eng light.
This will test the circuit to the pcm.
If you can get a scanner and capture fuel trims when ping is happening, see what they are It may point to a pcm flash code not proper for your elevation or load .

What were your plugs looking like also ?

Rich

 

After all this work shows the ping is not related to the knock sensor, I would have said it won't have an effect.
Knock is knock and NOT ping.
My guess is you have a leaky EGR or uncommanded EGR operation.
Here is the basis for the possibility.
If you put a monitor on the DLC port and watch the ignition timing, then use a hand pump to open the EGR, you will see the ignition timing go 'very' advanced as a reaction of the OX sensors to the exhaust contamination and signals back to the PCM to make that change.
Normally during regular EGR routine operation the fuel is cut back and the timing is advanced. This causes no problem in that normal routine.
If you have an exhaust leak when it's not EGR time, ping can be the result with to much timing and the fuel to rich at that time.
The reason fuel is cut back during EGR call is the exhaust gas will not burn the second time from it's effects in the stream so ignition can be advanced without ill effect. The combination of these two increases fuel mileage for that period of operation as well as cools combustion temps, reducing nit/oxides emissions. That's why it there.

Put a tee in the line to the EGR and do a test drive to see if it's a vacuum driven fault or the EGR is leaking exhaust gas by it's seat or both.
What you should normally see is about 3 to 5 inches of vacuum when your in normal cruise conditions. At idle none and heavey throttle,none.
The adjusting of octane by fuel changes, naturally changes combustion flame speed and affects to rate of ping but it's not the basic problem.