OP
chrisdvorak
Gold Member
okay guys got it scanned with a good scanner today, not autozone and got one code while the OD light was flashing P0720 output shaft speed sensor circuit
f350 5.4l stalling problem
- Thread starter chrisdvorak
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Diamondpilot
Super Star Member
- Joined
- Jan 18, 2007
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- Daleville, IN
- Tractor
- Jinma 254/284 Ford 861 Powermaster at work
There you go. Get the sensor and swap it out, clear the code, and give it a try.
Chris
OP
chrisdvorak
Gold Member
well after waiting 3 days for the sensor and installing it and clearing the code I still have the same problem, and same code comes back. however when I cleared the code the first time the whine from the TC quickly went away until I shifted to D and it came back. so I think its electrical I just don't know were to look.
HHR
Platinum Member
How did the connections and wiring look going to the sensor?
I found a post showing someone with a similar problem and it turned out the alternator was causing voltage interference. 2001 F350 O/D Light Flashing Code P0720 - Ford Truck Enthusiasts Forums
Scott65
Silver Member
Ok, I went on my shop program to pull up some wiring diagrams for you. I ran across a tip from another mechanic, a trans guy, that posted nearly identical symptoms on a customer's truck. A little less intermittent. He stated his scanner would lose communication, then the truck would die. And it would start misfiring right before all of this, every time. He speculated the computer was either shutting itself down or shorting out due to the misfire so he investigated that part first. Found 2 cylinders misfiring, the coils were somehow shorting out internally, backfeeding back to the pcm causing the problem. And apparently preventing it from setting a light for misfires.
So, you stated that the coils were new. Did this possibly start at or shortly after that? Where did you get them? I don't want to bash any certain brands. All I'll say is from bad past experience, my shop will never purchase parts, especially electronics, from the orange big box. Also, somewhere on your intake is probably a water pipe pressed into it. I don't know if it would be in the same place on a superduty. Most of the stuff I do in my shop are diesels these days. Check the back passenger corner. They had a habit of leaking water down onto that coil/wire.
If you can link this to the replacement of the coils, what you will have to do is hook it to a scanner with more than code reading capabilities. I don't know if said orange big box store will do it or not. What your looking for is "mode 6" tests. You need test ID 53, which will pull up cylinder specific misfires. You need to do this after the truck has been running with these misfires, same key cycle. So drive it to a store or shop and don't shut it off. Go through the list and hopefully you will find the cylinder that is misfiring, thus your problem.
Obviously I can't vouch for this personally. I don't recall having one do this. I've replaced hundreds, if not thousands, of these coils though. And this tip system is usually pretty reliable. These guys post these tips and questions on here knowing that one day they will need help too, so they don't typically make it up. Seems certainly worth looking into in my opinion. Your fairly close, swing by my shop and I'll hook the scanner up, haha. I've always wanted to go to rhode island
Edit: HHR and I were posting at the same time. I didn't read the link you posted, but I would guess they found that it was leaking AC voltage? Same theory as the coil issue. Good call. GM issued a TSB for several years/makes/models for that exact problem. Easy to check too, unplug it
OP
chrisdvorak
Gold Member
the coils are standard motor T series from rock auto I installed them about a month ago and they took care of my high RPM skip but I still have one at idle (been like this since I bought the truck 5 years ago) unfortunately I don't have access to a scanner that will check the coils (other than dealer) I will try unplugging the ALT. the plug to the sensor was clean and I added some electrical grease to make sure it had a good connection.
Is the truck shifting fine now, just running bad?
OP
chrisdvorak
Gold Member
it has actually always shifted fine the only hard shift is from park to drive (or reverse) when cold. other than that and the stalling it shifts normal
OP
chrisdvorak
Gold Member
well today I replaced the neg bat cable as it was rusty, and cleaned all grounds that I could find (4) I also checked the wiring at the shift lever and all was good there, checked fuses none were blown. I disconnected the alternator and started the truck on just the battery. it seemed to run a little better and the OD light did not come on as usual also the first shift from P to D was not as hard as before however the truck still stalled soon after. I am out of things to try other than take it to the dealer to put it on a scope.
Do you have meter so you can check the voltage and ohms at the OSS connector?
OP
chrisdvorak
Gold Member
sorry for the late response, as weather has been bad and haven't been able to work on the truck. anyway today I replaced the wiring to the OSS sensor (figured I would rule it out) but as luck would have it I still have the same problem. I was driving it today and it still shifts great into all gears. if I clear the code I can drive it no problem until I get stopped at a long light and it will stall with the same code po720, it has also started stalling in park? I am out of things to try and this is driving me crazy!
HHR
Platinum Member
I have a gut feeling that you are getting some kind of RF interference with the signals going to the PCM from the sensor. I would try wrapping the harness from the sensor all the way to the PCM with reflective aluminum foil to rule this out. Heck, cover the engine with the stuff. Maybe the new coils are somehow causing this.
OP
chrisdvorak
Gold Member
here is an update, I finally got a new code to come up for the throttle position sensor I replaced the sensor and it has not stalled yet! however I have noticed that with the new sensor the idle is about 100RPM less (just over 500rpm), like I said truck hasn't stalled yet but it has been on my mind.
OP
chrisdvorak
Gold Member
yes I did, and it did not raise the idle. I thought that the TPS sensor would have some sort of adjustment but I cant seem to find anything?
sld
Veteran Member
The only thing I can think of that would cause a low idle is the TPS sensor or the IAC bypass valve. The IAC is cleanable. I would take it off and blast it with carb cleaner and compressed air. Keep the cleaner out of the electrical connector. After cleaning (or replacing) reset computer.
The only other thing would be if someone messed with the set screw for the throttle plate. Despite the warnings it is adjustable. As a last resort I would do this:
1. run the screw in a couple of turns
2. disconnect the IAC connector
3. start the truck and adjust screw to correct idle (make sure it's at operating temp and might be idling as high as 2k depending on how far you turned the screw)
4. shut truck off and disconnect battery
5. plug IAC connector back in
6. after 10 minutes or so, reconnect battery and restart truck
I have never done this to the 5.4 but the same process works on many Fords that I have done. The IAC's sole purpose is to handle idle speed deviations (put in drive, compressor on, alternator load, etc..). The throttle blade always let some air in.
The only other thing would be if someone messed with the set screw for the throttle plate. Despite the warnings it is adjustable. As a last resort I would do this:
1. run the screw in a couple of turns
2. disconnect the IAC connector
3. start the truck and adjust screw to correct idle (make sure it's at operating temp and might be idling as high as 2k depending on how far you turned the screw)
4. shut truck off and disconnect battery
5. plug IAC connector back in
6. after 10 minutes or so, reconnect battery and restart truck
I have never done this to the 5.4 but the same process works on many Fords that I have done. The IAC's sole purpose is to handle idle speed deviations (put in drive, compressor on, alternator load, etc..). The throttle blade always let some air in.
Had a quick read, didn't see this mentioned, so wanted to ask....
When was the last transmission and rear-diff service done ?
If it's a 4R100, the service intervals aren't super-long, and old diff fluid can cause funky OSS readings if the contamination level is high enough.
Rgds, D.
When was the last transmission and rear-diff service done ?
If it's a 4R100, the service intervals aren't super-long, and old diff fluid can cause funky OSS readings if the contamination level is high enough.
Rgds, D.
OP
chrisdvorak
Gold Member
well today had the truck stall on me again while backing up a slight hill, I have removed and cleaned the IAC. trans and diff was serviced 30k ago and fluid is clean. I guess the TPS was not the problem just masked it a bit. this seems to happen now only when the truck is cold or more often anyway. and for that reason its making me think fuel injectors?
OP
chrisdvorak
Gold Member
there is 116k on the truck fuel filter was changed about 10k ago the fuel pump is original as far as I know, but I don't think its a fuel supply issue as you can put the pedal to the floor and it will take off at 3k rpm with no problem. this is the first i've heard of the coolant temp sensor could you elaborate?
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