Engine/Transmission (1998.5 - 2002) high idle

[PTuszynski]

Iam having an inconsistant high idle. it is sometimes as high as 1000rpm but most often its around 900rpm or so, it doesn't follow any pattern as far as outside temp. or driving condition. apps was replaced around 50,000 miles when dealer was diagnosing vp44 failure. My truck has 94,000 miles. I have limited resources to repair it myself so if I have some info to take to the repair shop would be great. Thanks!

 

[JLandry]

Without knowing how the dealer arrived at the VP44 being the culprit, it's hard to refute their diagnosis. There could be a dozen different causes.



Presumably they've gone through a series of tests and checks using a DRBIII Scan Tool and everything but the VP44 checks out normal?



You might ask if they've checked Camshaft Position Sensor. This is how the ECM knows what the engine speed is. If it has a signal present but is faulty, there might not be any diagnostic trouble codes yet the ECM would be "lied to" about the engine speed. Might be worth asking.



Good luck,



John L.

 

[PTuszynski]

I had the usual no power issue when I took it to the dealer for the pump at 50,000 miles. There were no codes or check engine light. I knew what was happening but they tried the replacing the apps before finally replacing the injector pump and the transfer pump to tank conversion. All has been fine until a month or so but the cam pos. senser does make sense. I'll check for any codes before taking it in. Thanks John

 

[JLandry]

Sorry... I misunderstood and thought the truck was at the dealer right now and they were recommending a VP44 replacement.



What year is your truck? I wonder if there's a Technical Service Bulletin which may cover this?



In the mean time, the first thing I would do (if you haven't done so already) is verify proper fuel pressure at the fuel inlet to the VP44. When's the last time the fuel filter was replaced?



Has it been for more than one tank of fuel and does it do it with fuel from different suppliers? Conceivably this could just be bad fuel.



When the engine idle is too high, is it stable (consistent), or does it vary (surge)? Does the engine idle smoothly?



Does tapping the accelerator pedal (briefly revving up the engine) change the high idle rpm problem?



When the high idle problem occurs, have you checked to make sure the APPS bell crank is closed against its idle stop? To do this you would need to take the black plastic cover off the side of the APPS bracket to expose the bell crank. I'm wondering if the accelerator pedal cable and / or the cruise control cable could be binding?



It's also not out of the realm of possibility that the APPS is going bad again. If this is the case, there's a cheaper alternative to replacing the expensive OEM APPS. The APPS can easily be tested with a DRBIII Scan Tool or a little more effort with a multimeter.



Regards,



John L.

 

[PTuszynski]

My truck is a 02, 3500,HO. When it idles high its consistant and doesnt surge. it idles smooth at start up. I drive approx. 20 miles to work, all freeway driving and when i get off the exit ramp it idles high. Its not consistant,yesterday it was 1000rpm,highest I've seen, at other times it is around 900 rpm. Tapping the pedal doesn't change it. But it also happens driving around town. The bad fuel could be an issue. I usually get fuel at the same station all the time but was only putting 40 bucks or so at a time. This weekend I filled up and the problem is back after being gone for a couple of weeks.

 

[JLandry]

I wonder if there's a Technical Service Bulletin which may cover this?

I checked but couldn't find anything.



John L.

 

[PTuszynski]

thanks for the help John, I'll post if I get it in and they find something.