I'm with you on the CPS is my starting point. The truck had been running on a long drive down the highway, my son said everything was fine until he came to the off ramp.

However, he had previously told me a couple of weeks ago it was trying to stall when he would shift into reverse. So I hope to find a vacuum leak as well, my reading online shows this could easily be part of the problem as well. Maybe the sensor took a while to go out completely??

I will update Saturday or Sunday depending on when I get home.

Thanks for all the help, this site is the best.

 

It has been a bit since we went over this but here is an update.

I went to my sons apartment and we tried lots of things to no avail.

1. Sprayed for Vacuum leaks
2. Replaced Cam Position Sensor
3. Wound up replacing the entire Throttle body, this included a new Throttle position sensor and IAC valve.

The symptoms are still this:

Start the truck cold, it starts right up and idles smooth. After it warms up it begins to stumble and run rough.
Once this process starts it generally dies. You have to work the throttle pedal to keep it going. If I reset the battery I can repeat this process.


I did buy a code reader and it was not much help, seemed like each time we scanned we got different codes, almost never repeating them.

Gave up on money and time and took it to the Ford dealer...
1. Diagnostics 1, "we can't find anything wrong, need more diagnostics"
2. Further diagnostics say nothing is wrong with wiring, coils, computer, vacuum lines etc.
3. They think there is an internal issue with the engine and want $600 more to figure this out. My son is already out $350 for the first two rounds to these guys.
I told him to go get his truck and get it home. He can drive it a couple of miles before it starts running rough.

I thought the Ford Mechanics would find something...any more ideas on what could cause this? I have done some reading about a Variable cam retention spring or something like that could be the issue...I'm lost. I am up for any ideas for I am stumped and the Ford guys are too...

Thanks.

 

Bump.

Anyone at all? Throw me a bone.

 

To me this means that this can't be an internal engine issue. If it's intermittent like this it really sounds electrical or a control issue. You say the codes were different, exactly what were they?

 

From memory, 1 time it was an O2 sensor, then it was Bank 2 running lean, then it was oil temp sensor out of range. I think there were a couple of others but those for sure.

All of these never showed up until after I replaced the Cam Position sensor, that was the initial fix. Truck ran great at first, we drove it down the street and it died. got it home and you know the rest.

I will ask my son if he remembers all of the codes.
He said he has the papers at home where we wrote the codes down, will get back to you asap.

 

You said you replaced the IAC valve w/ the throttle body, I didn't think the 3v engines had IAC valves?

 

I agree with Tom. If it were a mechanical issue with the engine's components, it would run like dog-poo all the time, not just selectively. I'd be looking for a bad ground, a short to ground on a harness, or a bad connector on the engine harness somewhere. I'd also check the harness at the ECU and make sure it's tight and there are no pigtails backed out anywhere. It *could* be a computer issue seeing as how your getting so many different codes from out of the blue, but I would highly doubt it. Looking at the ECU would be my absolute last resort.

 

Just thinking a bit more on this...

This engine has variable cam timing. What if the PCM was not seeing the cam position that it was commanding on this particular bank? I guess it could be a cam phaser, but I'm not sure of the typcial symptoms other than a diesel-like idling.

I know I overuse this particular smilie but...

 

In that light, here's some research I found. It pertains to the F150, but it's the same basic engine....

5.4L cam phasers.. What goes bad? - Page 5 - Ford F150 Forum - Community of Ford Truck Fans

"I signed up to be a member right after I bought my 2008 FX4. I've never posted anything. My truck had 59,450 miles on it when it started to act up. It was the noisey, chuggy, knocking sounds everyone else has been getting. It also would start acting up when it was warm and truck was slowing down to a stop in forward and reverse on occasion. It would almost die and motor sounded like it was letting go. I would put it in neutral and rev it up and it would go back to normal. I did a lot of research on this forum andf ound out just like everyone else it was the cam phazers. I took it to the dealer last Thursday and got it back today and it sounds like a new truck again. They replaces both cam phazers, vct solonoids and the valve cover gaskets. Here's the best part, Ford paid for it. It was covered under the powertrain warranty. They also replaced one of the exhaust manifolds too. It was starting to make noise when cold, and warranty covered the manifold also. I just want say there must be a warranty god for me. I'm glad it happened when it did, because I was just about out of warranty. I was expecting the worst and to my suprise everything worked out perfect. I also inquired about the noisey lifters right after starting the truck and they told me about the aftermarket oil filters. I had them change the oil and use the motorcraft filter and it fix the lifter problem instantly."

I also found this in my travels. It's a video about how the phasers work and talks about the noises commanly heard due to issues with them.

mms://multimedia.ford.com/seopts/Tech22_250k.wmv

 

Cut the cat off it and see how it runs. I am currently running a pipe straight back to my mufflers and it was bogging down running like ****. Took the cat off and it is night and day different. Mine had 128k on it when it started acting up.

 

I do NOT recommend this. Advocating a federal crime as a troubleshooting step just seems wrong, and if this were the problem the truck would run badly all the time, not just after it warms up.

 

Thank you for the input, I was hoping the cam phasers would not be the problem but it may be that is the case now.

The user from the F150 site, TWThomas1 has the exact same problem as me, of course he hasn't found the solution yet either...

I know there is no IAC, but there is a built in dohicky on the side of the TB, opposite of the TPS. not quite sure of its function.

This is beyond frustrating. I guess I can go over the engine bay, I tried to juggle wires and look at it running in the dark to see if I could spot an arc, no luck though...

 

I had a similar problem with a cam phaser. The truck would run fine until I ran it real hard, then it would feel like the phaser was getting stuck.

 

Just changed the plugs on my 06 f250. They have the same brittle ceramic bodied plugs. Do not attempt to take them out yourself because if one breaks (wich they do) you wont be able to take it anywhere.. make sure your auto shop has the tool to extract these plugs. When my mechanic took them out he broke 7 out of 8 plugs (wich is normal.) but he had the tool to take them out once they are broke. It can cost anywhere from a few hundred to over a thousand depending on how many plugs break...

 

I have this problem and when I read my post explaining what I think is causing it I realized two things:
1. It was so long it constituted a post hijack.
2. It was speculative enough that I need to see how my repair turns out before I advocate it.

For now I will just say that I think timing chain tensioner seal failure is contributing to my 5.4 3V stalling.

MOJoWales