Engine/Transmission (1998.5 - 2002) engine revs high at start up

[pwr2tow]

When I start my truck the engine revs high (ramps up rpm's) for a split second or maybe a second. I thought it was due to the edge comp box but edge replaced it for me and the problem is back again.



It started doing this last fall and it would do it about once a month. About a month ago edge replaced my comp for free because I thought the rpm surge on start up was due to the box. Well, yesterday my truck done the surge or high rpm's on start up three out of the five times I started it. It will set a check engine code but lucky me I got one of the few trucks that does not display the code so I will have to take it to the dealer to have the code read. I hate to take my truck to the dealer for anything because no one knows how to diagnose anything any more these days and all they want to do is change a bunch of $400. 00 parts before they find the real cause of things costing the customer a bunch of money unnecessarily.



Does anyone know what is wrong with my truck or have had this same problem? I am thinking maybe APPS.



The more I think about this it seems the problem came last fall when it was foggy and with spring thaw coming it has been foggy, I would relate this to a electrical problem but am unsure.



Ron

 

[HoleshotHolset]

If you are reasonably confident it is high-humidity related:



Get your throttle position sensor (or whatever you ISB folks like to call it... . ) and all of its associated wiring all the way back to the ECM soaking wet. Use beer..... heck if you like it even a little then your truck will love it.



Seriously - it sounds like a flaky TPS. Get a scan-tool..... hook it up and monitor TPS voltage on startup (with everything wet... ). Do the same test with everything dry. A 'wiggle-test' of all the wiring under the hood is also in order - you never know what you might come up with.



A somewhat flaky gound might also be the culprit.



Matt



On edit: Without an ISB to test..... I can't verify this experiment. When the truck is not acting up... you could experiment starting the truck with your foot ever so slightly on the throttle. If this replicates the high-humidity testing... then the TPS is telling the ECM to raise the rpm a bit when it's wet out - due to a faulty switch or associated wiring.