Maybe this is a dumb question but as I roll up to a stop my RPMs are at 900-1000, so when I brake its like trying to stop while on the accelerator at the same time. Make any sense? With my girlfriends truck, you let off the gas and the RPMs drop and you coast up to your stop. I feel like I will be burning through brakes. Could this be related to my bad plenum?

 

Try cleaning the IAC and bore in which it installs to , on the back of the TB.

 

might be a faulty IAC, might be TPS or could be a sticky throttle cable or butterfly plate.

warm idle with throttle closed should be about 600.

 

I had a bad pre cat 02 sensor that simulated the exact same problem. Changed out 02 and its stopped doing it. But just for the sake of general maintenance pop off your throttle body and all its sensors. Grab a can of carbon cleaner and make that thing sparkle give a wipe to the antler on the tps as well.

 

When did the tps grow antlers?? lol mine must be a 12 point then. lol could be a vaccum leak

 

Brand new IAC and I have recently checked all the other sensors on the TB with a multi meter and they are all good. Once I come to a complete stop the idle goes back to 600 like it normally does. But its almost at 1000 until I completly stop. I always heard a bad plenum is like a giant vaccuum leak, and I am thinking my o2 sensor is bad. Thanks for the ideas guys

 

When you tested the TPS, what were the readings?

O2 sensor may be the cause.

 

honestly I cant remember but it was within normal paramiters of what the Haynes manual said.

 

Disconnect the hose to the brake vacuum booster at the manifold. Plug the hole. Take the truck for a drive. (the brakes will be MUCH harder to apply, keep that in mind....) If the symptoms are gone, I would suggest a possible leak in the vacuum booster.

 

hmmm good idea. Might be the cause, when it is in park after a drive i get a "crackling/grinding" noise I can hear and feel through the steering wheel that I was told awile ago could be caused to a bad booster.