I was having a problem with my 1998 civic ex overheating it has 163,000 miles on it. I took it into a shop and they replace the head gasket the head was not warpped or cracked. The problem now is the car is not idled properly when I go down a hill near my house my rpm normally stays constant I noticed today the rpm was jumping the entire time down the hill. Also the engine sounds like it is racing when you cut it on. So I must ask what is the proper idle for 1998 civic ex because I'm taking it back to the repair shop. Also something else the mechanic stated that he had to adjust the timing on the car after the head gasket change so also I would like to know how can you tell if a car is out of time?

 

....car is out of time?
I dunno if you're talking about the timing belt or something, as a nub myself.
idling problem...does the rpm jump still when staionary on a ground?

 

Yes I'm talking about the timing belt yes I've seen it jump while being stationary

 

Please describe the idle surge more in depth. Be as descriptive as possible.