Joined: Oct 2015

Posts: 186

Likes: 5

From: Fairfield County Connecticut

Hi everyone, I apologize for the novel...

I posted a couple years ago that my idle was surging up and down after a radiator flush and fill. You guys said that it probably just needs to be bled and that did the trick. Smooth as silk after that.

I have since done another fluid flush and fill and bled the system and all was good. That was back in October I think. But about a week ago I cleaned out my throttle body because my gas pedal was sticking. That fixed my issue but I may have used too much throttle body cleaner or gotten gunk in a sensor or vacuum line or something because now my idle fluctuates repeatedly after it warms up. Only a little, like from 1000 rpm to the next hash mark...like 1250 rpm and down and up and down... If I hit the gas a bit the rpms are smooth.

Weird thing is, only when I'm idling and I hold my foot on the brake it does this. If I let go of the brake the rpms climb to about 1500 and stay there steady. BUT, if I hit the brake, have my headlights on and the heater blower on full it stays steady at 1000 rpm. I made a little video when I was waiting for my train so you can see some of the weirdness.

Any suggestions? I only brought up my coolant story because it kind of had a similar issue but my level is good. May not have anything to do with it. I assume it's the throttle body because it happened right after I cleaned it. I used throttle body cleaner that said it was safe for sensors. It did say use sparingly and I may have gone heavy handed with it.

https://youtu.be/CioSTuJSzJU

Thanks for the help!

Joined: Oct 2015

Posts: 186

Likes: 5

From: Fairfield County Connecticut

So I found a thread that was posted by Hugh Man I think the name was with the same issue. It was just the idle that needed to be brought down. These trucks apparently cut the fuel when the brake is applied over 1,100rpm. So the truck had a higher idle and when I hit the brakes it would lower down below 1,100 and then resumed giving fuel and the idle raised again only to be cut off again. This cycle repeated itself.

I checked for vacuum leaks with the same throttle body cleaner all around the intake duct, throttle body and vacuum lines just to be sure I wouldn't be masking an issue and found nothing. Lowered the idle to around 750 - 850rpm (stock is 750rpm).

All good! I love this site!

Joined: Jan 2018

Posts: 167

Likes: 11

From: Rapid City, SD