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Discussion Starter #1 (Edited)
Ok guys, I have an issue that 2 local diesel shops and 3 local auto shops have not been able to solve.

Randomly when driving my truck (usually after stopping at a stop light) I press the accelerator pedal and the tuck doesn't move an inch. The check engine light will light up and the Overdrive light will begin to flash.

If I continue to hold the gas down without letting up the issue will last FOREVER. The lights will stay on and the truck will not accelerate an inch. However, when I let go of the accelerator the issue goes away after about 3 seconds.

However, the shifting is now VERY rough and the RPM's drop steeply after each shift. (limp home mode?) I can fix this issue by pulling over and turning off/on the tuck.

This problem is honestly going to kill me one of these days when I pull out making a left turn and then cannot accelerate!

One of the shops decided it was the "Acceleration Switch Assembly" and replaced that for a staggering $242. The issue was obviously not fixed.

‪1997 Powerstroke Check Engine Light Problem.MOV‬‏ - YouTube

I have attached a youtube video that I made trying to show the issue first hand. At the first of the video I hold the pedal down for a while and show that the issue never goes away. Then after I release the pedal, it is reset after 3 seconds but then shifts are all out of whack.

I Appreciate Any Suggestions! I Am Now To The Point Of Replacing Anything It Could Be, But Have No Clue As To Where To Start.

THANKS!!
Scott

1997 240,000 Miles
 

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So through the first part of the video, you were pressing the go-pedal? And not only was the truck staying still, but the engine was not revving up? Correct?

If the engine doesn't speed up when you press the pedal, it's most likely related to the pedal position sensor. Remember, the truck is "drive by wire", the pedal is just a big electric "volume control" that sends a variable resistance to the PCM. In fact, that's what they probably replaced, and given it's probably $200 dealer part, that's not too bad a price. But since that didn't fix it, either they didn't do something right, or it's possibly the wiring between the pedal and the PCM, or a connector or something.

Just to help isolate the problem, next time this happens, shift to Neutral or Park, and hit the pedal. If the engine now responds to the pedal, then that's a little more complicated; it's as if the PCM doesn't respond to the pedal only when it's in gear. If the engine still doesn't rev up, then that pretty-much isolates it as a pedal/sensor/wiring issue, unrelated to the tranny.

The assembly also has a switch that senses when you've completely let go of the pedal; it's the "idle validation switch". It could be that it's incorrectly sensing either that you're always pressing the pedal, or never pressing it.
 

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very strange. Subscribing
 

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Discussion Starter #4
So through the first part of the video, you were pressing the go-pedal? And not only was the truck staying still, but the engine was not revving up? Correct?

If the engine doesn't speed up when you press the pedal, it's most likely related to the pedal position sensor. Remember, the truck is "drive by wire", the pedal is just a big electric "volume control" that sends a variable resistance to the PCM. In fact, that's what they probably replaced, and given it's probably $200 dealer part, that's not too bad a price. But since that didn't fix it, either they didn't do something right, or it's possibly the wiring between the pedal and the PCM, or a connector or something.

Just to help isolate the problem, next time this happens, shift to Neutral or Park, and hit the pedal. If the engine now responds to the pedal, then that's a little more complicated; it's as if the PCM doesn't respond to the pedal only when it's in gear. If the engine still doesn't rev up, then that pretty-much isolates it as a pedal/sensor/wiring issue, unrelated to the tranny.

The assembly also has a switch that senses when you've completely let go of the pedal; it's the "idle validation switch". It could be that it's incorrectly sensing either that you're always pressing the pedal, or never pressing it.

Thank you so much for your reply. Yes I was pressing the Go pedal for the first part of the video. It was all the way to the floor and not a dang thing was happening.

So you are suggesting that next time it happens, keep the gas pedal floored and shift to park/neutral? Remember if I let go of the pedal even for a second, the issue goes away, but I'm left with very strange shifting until the truck is turned off/on.

Maybe I should insist the shop replace the part again? And this time check out the wiring?
 

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So does this happen in all forward gears & reverse? When you depress the go pedal in the video you get nothing out of the engine?? No RPM's at all?? If it happens in all gears and there are no RPM's then i would agree that it is a PCM, sensor, or wiring issue. Your E4OD is completely controlled by the PCM so the fact that the PCM has it in limp mode after this occurs would say that the PCM is functioning correctly. The hard shifting in "limp mode" means that your PCM over riding the shift and pressure solenoids and applying full pressure to the VB.
 

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Discussion Starter #6
So does this happen in all forward gears & reverse? When you depress the go pedal in the video you get nothing out of the engine?? No RPM's at all?? If it happens in all gears and there are no RPM's then i would agree that it is a PCM, sensor, or wiring issue. Your E4OD is completely controlled by the PCM so the fact that the PCM has it in limp mode after this occurs would say that the PCM is functioning correctly. The hard shifting in "limp mode" means that your PCM over riding the shift and pressure solenoids and applying full pressure to the VB.
Yes, I was pulling into my neighborhood, pressed the gas and got nothing. Having had this happen numerous times I kept the gas floored and pulled out my video camera to get it in action. NO RPMS at all. It happens say 1 out of 50 times I press the gas pedal.

It has never happened to me in reverse, though it could just be by chance. (1 in 50) I'm not in reverse that much! Always seems to happen when i'm coming off a complete stop in traffic.

I'm starting to enjoy all the angry drivers behind me that start to honk and wonder why the heck i'm not driving when it's green.

When you say PCM, I'm wondering if that's what they replaced. My bill says this:

"Acceleration Switch Assembly" $103.36 for the part and $118.36 for the labor. I'm betting it was a 30 second replace.
 

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118.36 labor? It is literally a 5 minute job. That is RIDICULOUS. My vote is also on the TPS sensor.
 

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Remember if I let go of the pedal even for a second, the issue goes away,
Oh, I missed that part. What I'm guessing is happening there is that, when you let go of the pedal, the idle switch I mentioned above kicks in (it's either closed when you let go of the pedal and open when you press it, or vice-versa; I always forget), which "resets" whatever is going on.

The PCM is NOT the part they replaced. PCM is Powertrain Control Module. It controls the running of the engine and transmission. It's the counterpart to the ECM or ECU in other vehicles. The part they replaced sounds like the go-pedal assembly; the pedal, the position sensor (the "volume control") and the idle switch are all in one part. It took more than 30 seconds to replace, but not $118 worth of time. Probably 5-10 minutes. To confirm that this is indeed what they replaced, get the old part from them. In pretty-much every state, if it's not a part that has to be returned for core, and there are no hazardous materials involved, they're required by law to allow you to keep the old part. I wouldn't have them replace it again, because the problem is more likely a connector or the wiring; IOW, your original part may well have been okay.

It's acting like the idle switch is malfunctioning, like it still thinks the pedal is all the way up. A good diagnostician won't just keep throwing new parts at it, s/he'll TEST - put an ohmmeter or continuity tester on the switch itself, on the connector where the switch and sensor connect to the wiring harness, and on the corresponding pins on the terminal going into the PCM, and operate the pedal and watch what happens when.

Edit - waitaminit - the CE light came on? So, for the $118, did they at least scan the truck and give you the code(s)? They should have.
 

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Discussion Starter #9
Ok so you are saying if they replaced all that stuff I should have a new gas pedal? It has been a few months so they wouldn't have the part anymore, but I know I have my original gas pedal. They claimed that they needed to Borrow a fancy code reader because theirs wasn't finding any codes. They did not however give me the code.

Ill go back tomorrow and ask them to read it again. He is a friend of mine and is happy to do it free. The ford dealership wanted $70 to read the codes for me today. I passed on that steal of a deal.
 

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Discussion Starter #10
I'm just throwing a dart at the board here but I replaced the glow plug relay with an aftermarket one from eBay a month or so before this started. Surely that doesn't have an effect?
 

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Discussion Starter #11
Well as you can see we got nowhere again :( I traded the truck in yesterday for a 2002 7.3. I just couldn't deal with this problem any longer. It was going to kill me pulling into an intersection and then not being able to go! Hopefully if someone finds this thread in the future they can resolve the issue. Farewell 97....
 
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