blasphemy101

I can't watch your videos at work, but your description sounds identical to what I'm experiencing, but more severe (since mine has never stalled, or even gotten that close). I'm going to look through the service manual tonight to see if I can find a reference to testing the IACV. If covering the holes in the throttle body turns out to be a factory method for testing the IACV, I'll probably pull mine apart and clean it thoroughly over the weekend.

BlackFox

Cleaning mine didn't do anything. And since the entire intake (including the IACV) came from my old engine (which died to a cracked retainer dropping a valve) I highly doubt the IACV is the culprit. It worked perfectly on my old engine, so I would find it hard to imagine it got faulty due to a couple of months of non usage?

blasphemy101

My mistake, I read through your post too quickly, it looks like we're experiencing different (but maybe related?) problems. I just have a rough idle regardless of temperature - no hesitation or CEL.

I doubt your IACV would fail from just sitting around... Did you disassemble it and clean it thoroughly per Billman's writeup?

BlackFox

Yup

Maybe I just have a more advanced stage of your problem?

blasphemy101

I just got a chance to watch your videos. From what I could tell, your sputtering is much more constant than mine. Mine is way more uneven and "popping." If I get the chance I'm going to try and post a video tonight.

I heard it as I was driving slowly through a parking lot today, so I have my doubts about it being the IACV. I'm considering re-checking my valves - the exhaust valves on cylinder 1 were pretty tight, but I could still fit the smallest feeler gauge in the range.

I'm at such a loss...

BlackFox

I know how you feel...

BlackFox

Can anyone tell me how the engine should behave with the IACV disconnected?

When I pull the plug, the idle goes bananas bouncing around 1500rpm. Applying the throttle makes it even worse.
I thought it would settle with a base map at 500rpm or something like that? Or is this a normal reaction?

blasphemy101

Mine does the same - I would this is expected to happen. While doing this, I revved up the engine a bit and noticed the RPMs continue to rapidly bounce by a few hundred rpm as you sweep through the rev-range up until about 2500-3000 RPM. To me, this indicates the ECU expects the IACV to be functioning during this RPM range of ~850 - 3000 RPM. So the IACV might still be my problem, since I experience my problem in that range.

I checked up on the "plugging the two throttle body holes" method. The factory service manual indicates this check should be performed in a HIGH idle situation. It only gives two choices: if the car dies, replace IACV; if the car keeps running, check for vacuum leaks. I believe this check is for detecting if the engine is pulling in air from somewhere other than the IACV (vacuum leak). This DOES NOT look like an appropriate method of checking the function of the IACV in a low idle situation. However, if you think you have vacuum leaks, this might be an easy way to test for some big ones.

For low idles, the manual says to try cleaning the ports on the throttle body. However, they look rather large, so I can imagine they have enough crud in them to stop the IACV from functioning correctly. I'm going to pull the IACV apart this weekend and clean it very well.


I also tried these and didn't get any changes:

- Spraying carb cleaner down the MAP sensor channel in the throttle body
- injector cleaner (snake oil IMO)

BlackFox

Cleaning the throttle body didn't do anything for me either. But that's probably because me whole intake manifold and everything on it, isn't that old or gunked up.

I'm running my second tank of injector cleaner now (although the injectors were tested ok) and it does seem to be helping a little. Could still be my imagination, time will tell.
It doesn't only clean the injectors, but the entire fuel system (or so they say). And since my car has been standing outside all winter with the fuel lines disconnected and half a tank of fuel... it might actually do some good.

HvRRZ

I seem to have only recently started experiencing same symptoms described in this thread.

Idle sits perfect, but you can hear the poping in the exhaust and the vibration under the car(can feel it in the seat). Hesitation or loss of power at low rpm, very slight mid range sometimes but up top it's perfect. Engine revs smooth and sounds great.

Sparks plugs changed, valve adjustment done, fuel system cleaner ran once, new intake, compression check was flawless, coils checked by replacing with a good running cars coils, valve clearanced double checked and good.... at a loss really!

Going to unbolt and check the CAT. I feel like there is a chance if it bad and the comb is loose or melted then that could be causing all this.