Hey all, I have a 2001 accord sedan with the 4cyl sulev and automatic transmission. Car has sat for awhile and now has an idle surge issue.

- Car will fire up, idle fine for a minute or two, then begin to idle surge... rising and falling.
- Only behaves this way when the transmission is in park or neutral, when in gear it idles and revs normally.
- I have removed and cleaned the throttle body with intake cleaner.
- No visible vacuum leaks or missing hoses/wires

Wondering what the steps might be to diagnose the issue. I have been reading and watching videos... multiple causes for this common issue seem to be discussed, most of the time leading on a goose chase with not fix found. I am wondering what my order should be to isolate the issue?

My suspicion is the cold air idle valve... should i attack this first?

Whats the next cheapest/easiest things to try to fix this issue? Have you had this problem? If so, what fixed it for you?

 

Check and bleed the coolant.

 

Problem solved!

I removed the intake, removed the throttle body, removed the IAC Valve on the back of the intake. Valve was gummed up, I had to purchase a 5 point star bit to remove sensor. This valve is unique to the ULEV and SULEV models I think? I cleaned the valve with intake cleaner and moved it, wiggled it free, it was totally stuck and after cleaning it would click and rotate back and forth, opening and closing the valve easily. Re-installed and idle surge gone! Woot!