I just cleaned a sticky throttle body due to poor fuel mileage with the truck in my signature, now the engine has developed a surging idle when I get off the freeway. It lasts about twenty seconds. No surging idle when it's cold. It runs normally, maybe the idle is a bit high.

I've gone through most of the "surging idle" posts and realize it could be a number of things, I'm hoping somebody here at Yotatech has experienced these specific symptoms and may help point me in the right direction. I plan to start off by looking for vacuum leaks, plugged lines and bad electrical connections before I start replacing sensors.

I never realized how common this surging idle problem is and the number of things that can cause it makes for some challenging troubleshooting.

 

i assume that the truck has a working egr valve? i would test that system as well.

all you have to do is take off the vacuum feed line, plug it at the source, then put vacuum on the egr valve itself, while the engine is running, and it should nearly cause the engine to die, or at the minimum stumble badly.

 

I'll add that to the things to try. Thanks for the suggestion.

 

As soon as you figure it out, come fix mine. I can't make it stop. Been years n years.

I changed the dashpot and it went away for 3 weeks then came back. The truck just wants to do its own thing...

 

The combination of vacuum leaks and faulty EFI sensors is something every mechanic looks forward to...