Hi I have a 1995 Chevy Sub with 205k on the engine. I have had a surging idle problem and it seems to be a disappearing problem. It will happen once in a while then run good for a while. I really need help on this one I have no idea what is wrong. I have replaced some things. All of this was replaced after the problem started.

Coil pickup on distributor
Spark plugs
Spark plug wires
Cap
Rotor
Throttle position sensor
Idle air controller
The last two were replaced twice. Once with used parts off a spare engine then again new. After initial replacement each being 3 weeks apart it worked fine then started acting up again.

The rpms at idle or in gear at any speed will drop suddenly low it tries to stall then they surge back up. When this happens I obviously loose power and have gotten myself close to an accident a time or two. I was supposed to take this on a trip recently and wasn't able. The way it is it's costing me a lot of money. I need help please ASAP. Thanks a lot for any help

 

did you check the fuel pressure and map sensor?check the connection and voltage at the coolant temp sensor and the resistance hot and cold

 

With that many miles, the first thing I would have done is a Sea Foam treatment...maybe two of them!

 

my 95 hoe was surging it ended up being the egr valve caked up with carbon replaced that now she runs fine with 325,000