Throttle position sensor issues

[TMutziger]

I'm trying to help a buddy figure out a problem he's been having with his truck. It's an 04. 5 325hp, 48re with an edge juice and has about 120,000 miles. He said about a year ago it started doing what he described as a "weird surging" while driving at hwy speeds with the cruise set. After several trips to the local dealership, they finally determined it to be a faulty throttle position sensor. He said they replaced it and the truck ran great till now. He said it is doing it again and has been getting worse. He says that with the cruise control set, it acts like it can't decide what speed it should maintain. It will surge back and forth and he said the throttle pedal jumps up and down erratically. Also boost is erratic with the speed surging. No codes have shown up yet. I know this might be kind of a vague description of symptoms, but I haven't had a chance to drive it myself. Any ideas? He thinks it's the tps again. If so, is there some reason why it keeps going bad?

 

[rscurtis]

With the throttle pedal moving, I would look for a mechanical problem with the cruise control servo and associated cables. You could also have a problem with the vacuum pump.



How does the truck run without the CC engaged?

 

[TMutziger]

Where is the vacuum pump and what does it look like? I'm not familiar with that on these. My friend says that when he drives without the cruise, he can control it if he concentrates on it, but it's still not how it should be. It's worse or more noticeable at steady highway speeds. I really need to drive the pickup and see firsthand what's going on but it is 300 miles away for the weekend. I won't be able to get my hands on it till next week sometime.

 

[rscurtis]

It's right behind the passenger side battery, looks like a miniature air compressor.

 

[TMutziger]

Still haven't had a chance to drive the truck myself to see what's going on. Just wondering if anyone out there has had similar symptoms or ideas on what might fix it. Thanks

 

[TMutziger]

No one else has any helpful thoughts?

 

[JJPage]

He could try re-calibrating the sensor. Disconnect the batteries for 20 minutes, after re-connecting them, turn on the key but do not start, slowly depress the accelerator pedal all the way to the floor, then slowly let it back up to idle position, do this 3 times. Turn the key off, now start the truck and test drive.

 

[TMutziger]

Thanks. I will have him try that.

 

[blacksheepdiesel]

An 04. 5 could have vacuum cruise or electronic cruise.

The vacuum APPS will be mounted on the front of the cylinder head.

The electronic APPS is under the driver side battery.

Does he have gauges including fuel psi and/or rail psi? If so, what are the readings during cruise when it acts up?

If the APPS is on the cylinder head and is determined to be faulty then buy an aftermarket replacement from timbo here on TDR. Much less expensive and possibly higher quality.

The symptoms do sound like what happens on my '01 and a new APPS always fixed the problem. The factory ones are really cheaply made.

Godspeed,
Trent

 

[TMutziger]

It has the vacuum APPS on the cylinder head. No fuel pressure guages. A good friend of his is a mechanic at a large dealership and has a scanner that will read rail pressure. He checked it once and said everything was in spec. I will have him check it again while it is acting up. Thanks very much for the info. I'll look into a replacement from timbo also.

 

[TMutziger]

I was just on timbo's site and it looks like the sensors he carries won't work with the cylinder head mounted APPS. Are there any other suppliers you would recommend?

 

[befrazier]

I had a similiar problem with my truck. Some of the responses that I got from TDR members are on this post already. One other was to change the fuel filter. I bought a new and it was doing the same thing. I ended up unplugging the tps, under the battery and cleaning with some electrical cleaner and adding dielectric grease to it. Put it back together and no problems since.

 

[JJPage]

I was just on timbo's site and it looks like the sensors he carries won't work with the cylinder head mounted APPS. Are there any other suppliers you would recommend?

Yes it will work on the engine mounted APPS, here are two links:Installing a Timbo APPS sensor ,



Timbo APPS , Jess

 

[blacksheepdiesel]

Send a pm to timbo, he will help you. It should be the same one that fits an '01/'02.

Godspeed,
Trent

 

[TMutziger]

I see that it will work. I just read it wrong, was in a hurry. It looks like thats the ticket. After gettin ahold of one and installing it, i'll let you know if it fixed the issues. Thanks to all for your help.

 

[befrazier]

I talked to timmbo apps guy and he made me a new pigtail plug that plugs into the apps sensor under the battery box. I had a guy take the old plug off and install the new plug. He noticed on the old plug that there were two pins loose inside of it. The truck runs great now. Any of the trucks that have the apps under the battery and is having the reoccurring codes may need to check this out. I have had this issue for several years and have bought two sensors with the same problem coming back. I had the guy check out the older apps sensors and they both worked fine. Hopefully this long process, trial and error, determination and the help from TDR and timmbo apps my problems are gone.

 

[befrazier]

The APPS problem came back a couple of months after the pigtail replacement. Although I needed to replace the pigtail anyhow. I unplugged the two big electric plugs attached to the firewall on the drivers side, cleaned with electronic cleaner and put dielectric grease on every small pin hole and plugged back in. I was reluctant to post for quite some time after I did this because of the past failures. I have not had any problems for approximately 9 to 10 months now. Hope this may help someone.