My engine is not going straight to idle anymore. I will wander around, jumping up and down between 650 rpm and 1000 rpm. Also on startup, it will rev up more than it should (I think).

'02 4.7L 150,000 miles

Any help please?
Thanks
David

 

replace the TPS, you will probably get the surging at a steady cruise speed too (especially with the cruise control on)

this is the most likely issue

 

First off clean the throttle body and the Idie Air Control valve.

Then replace these parts in this order as they play a roll in the idle quality,

PVC Valve
IAC
TPS, where if you have a problem here you will probably have problems at speed too.

I have the same problem as you. I don't have any problems running at speed, cruise or not. I replaced the plugs and PCV, cleaned the TB and IAC. My next step is to replace the IAC, then if that doesn't solve the problem then the TPS.

P.S.
I had a 96 S10 that had a similar problem, GM did all kind of PCM flashing and whatnot and it turned out to be the O2's.
Food for thought.

 

Clean the TB, move to the IAC the finish with a TPS if needed. Remember to reset the PCM each time you each thing:

To reset your engine codes:
Remove the negative terminal of your battery (10mm wrench).
Turn your ignition key to START and hold it there for about 15 seconds.
Turn your ignition key to OFF and remove it.
Connect the negative terminal of your battery.
Start but do not hit the throttle. Idle for about 10/15 seconds then turn off.
Restart the truck and drive as usual. It will take at least 12 starts and 48 miles to fully retune the computer. Hard Codes leave a shaddow for 40 full cold starts.

 

McStealth, replace your TPS sensor like shrpshtr suggested.

It's a $35.00 part at AZ and it fixed my surgeing problem.

 

Question please:
First clean the IAC and TB, re-install, then test. If the problem still exists, then replace the IAC first? Not the TPS? Any way of knowing before hand which of the parts is actually in need of replacing before buying both?

Thanks for replying.
David

 

Clean the TB, move to the IAC the finish with a TPS if needed. Remember to reset the PCM each time you each thing:


HS, I am a very literal kind of guy so I need to ask. Clean the TB, then clean the IAC? Not quite following what you stated? Sorry.

David

 

in some cases you can get away with just cleaning the IAC in order to solve the problem, but idk of any tests for the sensors off the top of my head . . .

 

Okay. I now need to ask where the IAC is located...

Thanks
David

 

Well here is the instructions for the 5.9L and 5.2L but not the 4.7L that you have, but maybe that can help you. https://dodgeforum.com/forum/1st-gen...ttle-body.html