surging idle

[R&D man]

I wanted to investigate a few things before i sent my car to get a smoke test.

I was playing with the fuel pump relay while the car was running and found that I could create the surging idle problem of reving to 1200 and back to 500 over and over.
I unplugged the relay and the surging started.
would my surging be caused by the fuel pump
it only started doing it as the car got warm
any thoughts
i am beginning to think it is not a vacuum leak

[tonywonder]

is this surging happening during warmup from cold after the car has been sitting? or is it happening while its already warmed up? or after its warmed up? does it stop after its warmed up?

My honda for example when its cold and i start it up. If i drive it before its done warming up and then come to a stop the idle will fluctuate. this stops after it has finished warming up. It has something to do with the engine temp.

This may be something similar in your case but I would also check to see you didnt short something out when you unplugged the relay.

As for the vacuum leak its still very possible this is what it is, one thing you could do is take some brake cleaner and spray it around the hoses to see if the idle changes speed based on that. if it does then u have a vacuum leak.

this may not end your issue because there could be more than one thing happening but atleast you know you have dealt with one issue.

and yes i would assume that by you unplugging the relay and the surging starting at that point, that it could be cause by the fuel pump. Only if this is what made it start to begin with. If it was doing this before you started fidling with the relay its possible it has nothing to do with your fuel pump.

thats my opinion.