2005 Ford Excursion
6.0
252,000 Miles (65% highway)
EGR deleted 2 years ago

Always Maintained (scheduled or repaired immediately when necessary)



When driving the engine goes to idle. If I lift foot off fuel and re-apply engine works normal. The problem keeps repeating. No problems starting or rough running. I have the truck at the shop and the gremlin causing this issue is elusive. Everything reads normal when hooked up in the shop. When the problem occurs on a road test the scanner screen blacks out. When you get off the fuel and re-apply scanner comes back on. Of course there are no codes because scanner blacked out and scanner reads normal after foot off fuel and re-applying .

Five years ago the windshield was replaced. About a year ago I started noticing Intermittently after a rain I would see a small amount of water on the drivers floormat. The tech pulled the fuse box and found substantial corrosion including several connectors. These were replaced, no help. Also last April I was caught Ft Lauderdale during the (freshwater) flood. Truck was operated at times in water slightly above wheel hubs.

The tech has been in touch with other Ford diesel techs one with over 40 years of experience. One recalled encountering this problem once. After numerous attempts to fix his customer called it quits and sold the truck.

I might be at the stage of starting to throw parts at it. I really don’t want to but I absolutely don’t want to ever sell the best vehicle I have ever owned.
I’m thinking of starting with the ECM or TPS. Any suggestions would be helpful.

Thanks

P.S. As prevented maintenance fuel pump was replaced in February 2023

 

Post a video of this issue as it's happening if you can, sounds like electrical system is buggerd.

 

Do you still have your dash gauges working when this happens? I'm thinking you're completely losing power and you see the idol RPM just because the engine still has that momentum. Maybe check all your grounds? I had this happen when one of my battery cables was loose

 

Are you sure it is actually going to idle, or just indication? I had a bad instrument cluster and would get all kinds of erroneous indications. Everything from rpms that I knew weren't what was actual and speed indication of way faster or slower than what I was doing. Temp, pressure, boost simply had a mind of their own... I ended up monitoring EVERYTHING that was on the cluster with Torque Pro for a couple of days because I needed the truck on the road. When the truck "goes to idle" do the windows and power door locks still work? How about the radio?

 

I doubt the technician is able to provide a video. The head scratcher is his computer screen freezes on a test drive when the event occurs and whatever is causing it is not displayed. Let off the fuel and reapply and computer diagnostics work fine. The diagnostic computer has been checked and there are no issues. It only happens on my vehicle.

 

IP has been removed and checked out. No issues noted. All grounds have been replaced. I will ask technician to test drive and try shifting to neutral when issue occurs to confirm engine is at idle. Thanks for the suggestion.

 

IP has been removed and checked out. No issues noted. All grounds have been replaced. I will ask technician to test drive and try shifting to neutral when issue occurs to confirm engine is at idle. Thanks for the suggestion.

 

When several Accelerator Pedal sensors have faults, the engine can default to idle.

I can't imagine that there aren't any codes though.

 

There have only been two codes. One was a slight cylinder imbalance which would not cause this problem and the other was a fan clutch code. Clutch has been replaced. We're confident that the problem of no code being set when event happens is because diagnostic computer freezes up at time of event.

 

It sounds like it is doing it regular. Which, while annoying, should make it a little quicker to diagnose. Is it every time the engine rpms build? Heavy throttle when the engine torques over some? Cheapest place to start is with power and grounds starting with the batteries. It sounds like you have a mechanic looking at it so hopefully the basics are covered but IDK. Running in deep water would be a good reason to really check out grounds (Did he really do all of them?) and maybe connectors that might have been submerged. Engine harnesses need to be wiggled to try to get it to act up. Monitor supply voltages to PCM with a meter.

 

Thanks for input. Replaced both batteries with Odyssey AGM's. All ground straps were replaced after flood and have been checked as a possible problem. Issue occurs during all phases of operation, highway or around town on surface streets. I'm going to ask the technician if he can reach out to his diagnostic company (not sure of the name, starts with an F) to see if they can suggest what components on the vehicle could cause his software to freeze up and not collect / display all parameters of the vehicle systems. I'm wondering how many sensors if any are in conjunction with the TPS.

 

The TPS (accelerator pedal) has 3 independent sensors (3 independent signals to the PCM). A failure of one will allow normal operation to continue. As I posted earlier - failure of any two will force operation at idle only.

If i were me, I would get ForScan (full version on a Windows laptop, or even the Lite version on a smartphone) ASAP and do my own checking for codes.

 

This thread may help a bit.
https://www.powerstroke.org/threads/...#post-16524097

 

Thanks for the input. My technician has his own shop and works on Ford only. In business over 10 years and with ford for 7 prior to that. He has the full ForScan. In the USAF I was a crew chief on H-53 helicopters and have an Automotive technology degree. Unfortunately my degree was for gas engines and was in the 80's. At 70 years old my training on aircraft and automotive education allow me to comprehend most of our conversations. He is good, thankfully, at speaking geezer on things I'm not clear on. I think I'm going to suggest replacement of the 3 mentioned sensors before I throw a PCM at it. He's extremely dedicated and it has become a personal challenge. He has the I won't be beat mentality. He has a lot of time on it he refuses bill me for. A very rare thing nowadays.

 

The three sensors are all in a single part

8C3Z-9725-A - w/o adjustable pedal
5C3Z-9F836-AA - adjustable pedal

I would check for wire harness chafing at the pedal and where it passes through the fire wall.