Alright, so this is an ongoing saga with my 99 civic. I thought I had a bad TPS, so I checked, it seemed to have a blip right in the middle was the TB was closing and opening. I replaced that, tightened the throttle cable and that seemed to have helped with the shuddering. However, still having a side issue, that presents like a bad IACV. The engine rpms surge up and down, only about 3 or 4 times, and only when starting it after its warmed up, that I have noticed so far. It doesn't do it if its cold. I have recently replaced the IACV with a new OEM and it seemed to move normally when I checked it while replacing my TPS. Any other thoughts what could cause the idle to go up and down?

 

The D16Y8 engine in a 99 Civic EX has a unique fuel injector air intake system. Have you checked for a leak in the hose that runs to the IM?

 

Didnt know that, I'll check it out.

 

Don't tighten the throttle cable too much. It has to be slack so the throttle plate fully closes when no one is pressing the gas pedal.

Did you calibrate the new TPS?

 

Yeah I had to back off the throttle cable, although I think its still a little too loose.

I did calibrate the new TPS.

 

 

Had to replace the rear brake lines, front to back recently. While hooking up the new lines I noticed some loose vacuum hose. I could not find where it went, but when I lowered the car I noticed it attached to the IM, near the bottom. I plugged it in and so far ok, although after messing with my gauges it was surging again but hadn't before that, so I think that's the problem. Thanks for the help, we'll see how it holds.

 

Well idle issue is back, but sporadically. Thanks for the diagram. I didn't check that line specifically but I will now.

 

I believe a bad fia will trigger a check engine light

Make sure you properly burped the cooling system when you installed the idle air control valve, there could be an air bubble right in the idle air control valve messing up its temperature and air calibrations

 

I might try that again, although I bled it for 45 minutes.

Yeah, I wasn't sure how to check if the FIA valve was bad, will have to google it.

Ok, found a way to test it, according to FSM, I am assuming if it fails the vacuum test it needs to be replaced?