The car seems to ONLY surge when its at operating temperature.

It usually start's when im 2 min into driving, not much when its just sitting there idling. Itll Throw a CEL after driving it for like 15-20min with this idling issue.

Ive owned the car for 2 years without ANY issue at all as far as idle surge or a dirty IACV.

The car just started doing this 3 days ago after screwing with the idle (trying to raise it a bit since its been sat for 2 months straight sounded a bit low).

After it sat for 2 months and i got it running it didn't have that issue. The next day i tried raising the idle by the "throttle body stop screw" and this issue started.

Do i just need to mess with the idle speed screw on the Throttle body? Or do i need to clean the IACV?

Car is a 1999 civic dx

 

I have the same issue when I start the car up. Just started 2 weeks ago. Jumps between 1500-2500 for 3 minutes before settling at 2K rpm, then settling down to 750-1K idle. When I drive for a few minutes and come to a complete stop, it starts again. This time between 1K-2K rpm, but the surges aren't as powerful as the warm up. Then, it completely stops.

Going in for an oil change tomorrow and they are looking at it. I'll report back tomorrow. Can't be much, as the car operates flawlessly otherwise...

 

I believe you are supposed to start up the car with the service connector jumped, and then adjust the idle. the exact procedure is in the service manual, i would write it out but i dont have it in front of me right now.

 

Same here. It's just the most annoying thing ever, and im in the process of selling the car so i want it to be in tip top shape so i can show it. Id really appreciate it if you posted back how you fixed your issue.

I dont think the scs has anything to do with my idle issue...

 

For some reason i was thinking of setting the timing, see attached. If it still has issues, then cleaning the IACV and FITV might be in order

 

Check your tps sensor. clean your iacv, fitv, and throttle body

 

The diagram does not apply to a 99 Civic.

The throttle stop screw is set at the factory and should never be tampered with. It may be difficult or impossible to get it back to normal.

 

Yeah just assumed it was a 92-95, here is the 96-00 pages

 

The relevant diagram is the second from the top (D16Y7 engine).

 

To the OP, very sorry for the delay in responding. Fell sick shortly after posting, and rescheduled my car appointment for today.

To reset the stage my car has been experiencing fluctuating idle at warm-up, varying from 2K-3K RPM and dropping to 1K-2K when warm. Occasionally the car will settle at 1500 RPM before I start driving. But once I drive for a few minutes and come to a stop sign, the fluctuation returns.

The Honda dealership ran a battery of tests, including checking for the FITV, and tested my IACV, sensors, checked for vacuum leaks, full coolant flush/test. All checked out fine. Except the ECU. A new one was installed for testing; bingo. It's kinda puzzling, since I would have expected the IACV to have been the culprit. But, I'll be picking up a P28 ECU for replacement next week and see how things go!