Pretty sure it's my IAC, what do you think?

[magnux]

Recently, my car has been a little "quirky" at idle. I've noticed it's more common on colder days (in Miami, "cold" is between 50-60* FYI). When I start the car in the morning, the RPM's are generally just under 2k, and they'll sit there for a while. Occasionally, they'll slowly go down about 200rpm, then back up. Once I'm moving, it seems fine.

The most irritating effects are when I either let off the throttle and coast or come to a stop. Sometimes, the engine will cut off if I let off the gas and start to slow down. It will chug a couple times, then just completely die. It restarts fine. What's more common, is when I come to a stop the car will bounce the idle to just barely stalling. It'll drop, jump up, drop jump up. I need to keep my foot slightly on the gas to get it to stablize -- which is annoying to do at every stoplight.

The problem is random, and can sometimes be fixed by turning the car off, and restarting it. That can occasionally keep it at bay for an hour or so.

I've checked for vacuum leaks, and none were found. I've replaced the following parts:

Spark plugs
Fuel injectors
Fuel pump
Fuel filter
Engine mounts
Transmission mounts
* Had a NASTY exhaust leak fixed at header, also.

(Note, these weren't replaced in hopes of fixing the above problem -- they were replaced due to just needing to be )

My fuel system is peachy, so I'm sure that's not the problem. I'm torn between it being my IAC, or possibly, my BOV. As I understand, venting to atmosphere can cause idle problems. I've removed my manual boost controller, and connected all the stock gear and I'm about to remove the BOV and IC and return it to stock as well -- to see if it helps or not.

So.. what do you think?

[BAC5.2]

Sounds like my IAC problems. My car would idle at 2000 RPM's and stall when I would put it into neutral and slow down.

It would chug and chug, wanting to stall all the time, and I'd get fuel cut if I would slam the throttle open.

I replaced the IAC and the problems were still occuring, and fixed the wiring and everything was solved. The car runs better with the new IAC, though, than it EVER did before with the stock gear. It idles smoother, even though I have all grp-n mounts and a lightweight flywheel, than it did when the car was stock as a rock.

[Brat4by4]

First, it sounds like you need to reset the ECU. Do that. You need to make sure you get a true reset. Then when you restart the car for the first time with a fresh base map. Turn on multiple loads so it will learn to idle with that stuff on (A/C, HVAC fans, headlights).

Do all of this before screwing with the IAC valve. Most people touch that thing without really needing to, and end up with their pockets a couple hundred dollars lighter.

[vrg3]

Definitely go back to a recirculating BOV setup. It's very easy to imagine how an atmospheric BOV could cause trouble like this. Even if the valve is normally closed at idle, it does still cause bad air/fuel ratios during shifts. And when the engine is coasting, the extremely strong manifold vacuum could still be making the valve open even if it shuts at idle.

Recently, subyluvr2212 had problems kind of a little like this, and found that they were correlated to unsteady system voltage due to a bad alternator voltage regulator. You might want to get a voltmeter and watch the system voltage to look for any weirdness.

[magnux]

I did forget to mention, I did install a new alternator, too. That fixed a few problems. Namely, the battery light would pop on at night occasionally when I had the headlights on.

[vrg3]

You still might want to check it out. subyluvr2212's alternator was pretty new too. But I guess if the problem existed before and after the alternator swap that's probably not it.

[BAC5.2]

Just for reference, I'm running an atmospheric BOV, and don't suffer and of those issues.

[azn2nr]

as long as your bov is shut durring idle that should be fine. my idle is rrough and i dont know why but nothing else is problematic so im leavin it alone.

[hijack] id kill for a low of 60 degree temprature. scraping my windows in the morning isnt my idea of fun. espcialy when there seems to be 2 layers of ice one only thicker than the last [/hijack]