cityjack

Evening all,

After the car warms up, it runs great. Idles at about 750 to 800 and does not stall at all at stops. Car is solid after warm up and from then on.
At start-up when cold the idle bounces from ~1300 to ~1100/1000. Again the bouncing idle goes away after it gets up to temp. I have checked for vacuum leaks. None. I have checked for proper level of antifreeze and air bubbles. Good and none. I have removed the IACV and went to clean it but it was perfectly clean. I put it back on. I opened up the FITV plate and screwed the plunger in until seated and then backed it out a half turn. Closed the plate on the FITV and still the idle bounces at the same rpm range.
Following the Helms, today I removed the air pipe inlet to the throttle body. I wanted to check the upper and lower air ports in the throttle body. At cold startup I covered the lower FITV port. It was definitely sucking in air good, but when covered with my finger, the idle still bounced. I then covered the upper IACV port and it stalled the engine. I started it back up and then let it idle and got the car up to temp. I then covered the lower FITV port again and now it was not sucking air. The FITV was working by opening and then closing once the wax plug swelled from hot water. By now as the car was up to temp, the Helms says by covering the lower port if the idle drops the FITV is leaking. The idle stayed steady. I then covered the upper port and it dropped the idle and would have stalled the car if I didn't take my finger off. I then while still at temp removed the IACV 2 pin plug. The Helms says the idle should drop. Mine stays the same at 800 rpm and steady.

I have no codes nor do I have a check engine light. I am stumped. The Helms says by the idle NOt changing whern I removed the 2 pon plug to the IACV I need to replace the IACV. What is the story here do you all think?

I am trying to look at this diagram of the throttle body and understand what the FITV and IACV do differently from eachother. I guess the FITV is totally mechanical and the IACV is electro-mechanical taking input from the ECm as well. But what is actually happening by the idle bouncing at cold start-up?

One more piece of maybe relevant history. I just got the car and the PO had fantastic service records that I now have. Good or bad, everything was done at the dealership, including oil changes. the PO complained of the same problem that I am now having with the stalling and the cold startup idle issues. The dealership found a bad IACV and recommended the IACV to be replaced. The PO declined it says on the paperwork from the dealership so the tech decided to adjust the idle it says. Whatever the heck that means. Who knows what he did instead of replacing the IACV like the tech wanted to.

Lastly, on a previous 3rd gen B20 lude I had, when I had this bouncing idle issue, i would open up the FITV and screw it back down all the way to seated and close it up. I would not back it out a half turn or anything. The car would run great. I have seen where people say to back the FITV out anywhere from a half turn to a turn and a half. Any ideas here?

Thanks and have a nice night.

Sid

thirsk66

iTrader: (2)

The answer is right in front of you. Replace the IACV especially if you have done the tests per helms manual and it failed. And a huge compelling item is the paperwork where the past owner denied to replace the iacv at the dealership. The only way that tech could have adjusted the idle is the idle adjustment screw on the throttle body, its the little gold flat head screw right below the map sensor. I would just replace the iacv and solve your issue. If you have the cash buy a new iacv but if not then a used one is just as good.