Theory: Meth Kit fouling up the Idle Air Control?

[SirThomas88]

Lately my car has been idling at low RPMs, and sometimes almost stalling when I come to a complete stop. Usually this occurs after boosting (my meth injection kit is activated at 1psi boost).

I cleaned out my Idle Air Control assembly as best I could, and the problem didn't reoccur for a few days (even after boosting). Then last night I did some hard boosting and came to a complete stop about 20 seconds later, and sure enough my car almost stalled.

My Theory:
I'm wondering if since my meth is injected immediately before the throttle body, if it is blowing down into the hole in the throttle body and the liquid is fouling up the Idle Air Control valve. I'm considering getting a TB spacer and drilling a hole in the side of it and relocating my boost cooler nozzle there.

What do you think?

P.S. Also, when this low RPM idling is occurring, often my Air Fuel Ratio gets very very lean (above 18:1). Not sure if this is typical with a faulty IAC valve or if it means something else is wrong.

Thanks to GregTRD for walking me through how to remove and clean the IAC valve.

[Akfahad]

have you replaced the IAC lately? I know when my car hit a little over 100k, my IAC had to be replaced. I've got two nozzles, one before and one after the TB and don't have the problems you are experiencing.

[ToyoSolV6]

i experience that problem as well and i dont have meth it just happens to me after im boosting too much.

[SirThomas88]

have you replaced the IAC lately? I know when my car hit a little over 100k, my IAC had to be replaced. I've got two nozzles, one before and one after the TB and don't have the problems you are experiencing.

Well I got the car at around 140k miles, so I don't know if it was replaced before then. However my car just reached 170k, and in that time I certainly haven't replaced it. I only cleaned it out recently but that clearly didn't fix it.

Do you know what goes wrong that it needs replacing? I'm assuming it has something to do with the moving parts, as it includes spring(s) and a magnet. On RockAuto.com it seems the IAC sells for around $140, which sucks but if I can be sure that that's the source of the problem I'll do it.

i experience that problem as well and i dont have meth it just happens to me after im boosting too much.

I'm glad I'm not the only one who has this happen after boosting, but I guess it's not the meth. Do you have a wideband AFR gauge? And if you do, does it sometimes show a very lean condition while this occurs?


Thanks for the post you guys. Trying to learn as much as I can about the issue so I know how much I should be worried about this and what to do about it.

[ToyoSolV6]

Dont have an AFR gauge so i wouldnt know if i start to run lean, but im pretty sure it could just be our IAC since you mentioned you havent changed it. and i havent either, and its never been cleaned.

[SirThomas88]

That's reassuring. I wonder if perhaps it happens more often after boosting due to increased vacuum pressure going through the IAC valve, forcing it to stick more frequently.

If anyone else has had an issue with this please do tell!

Thanks for posting. I think I may just go ahead and buy a new IAC valve. Or maybe I'll just ignore it lol. But an air-fuel ratio of above 18:1 is concerning.

[ToyoSolV6]

yeah that really is something to watch out for, i would recomend getting a new iac, and seeing how it runs from there.

[hskrsolara]

damn, I have the same problem. after running really hard, boosting, when I come to a stop my idle drops down around 450-500 and I have to pop the throttle to bring it out of the "funk" and it is real damn annoying. Maybe I need a new IAC as well. Good tip!

I still haven't put on my meth kit, but plan on doing so soon with my 6 psi pulley. It'll be nice to get this out of the way before I hit the dyno.

[SirThomas88]

great that we're getting all this info. interesting to hear it's more widespread than i thought. Gabe said he remembers having this happen to his red Camry too back in the day.

It's great that we're learning something from this. Hskrsolara, you don't happen to have a wide band AFR gauge do you? I notice my AFR tends to get very very lean when this happens. Something to keep in in mind.

[ToyoSolV6]

damn, I have the same problem. after running really hard, boosting, when I come to a stop my idle drops down around 450-500 and I have to pop the throttle to bring it out of the "funk" and it is real damn annoying. Maybe I need a new IAC as well. Good tip!

I still haven't put on my meth kit, but plan on doing so soon with my 6 psi pulley. It'll be nice to get this out of the way before I hit the dyno.

lol looks like we are not the only one's, but yeah im planning on throwing on meth with 6psi as well. But i would really like to get this fixed before i actaully do it because i really dont want this happening when i get excited and decided to floor it lol

[hskrsolara]

great that we're getting all this info. interesting to hear it's more widespread than i thought. Gabe said he remembers having this happen to his red Camry too back in the day.

It's great that we're learning something from this. Hskrsolara, you don't happen to have a wide band AFR gauge do you? I notice my AFR tends to get very very lean when this happens. Something to keep in in mind.

yep, I do have an aem wideband. when this happens, my a/f jumps off the charts (red). LEAN. I'm getting an IAC asap!

[02slera]

anyone who replaces the iac,
please post up and let others know if it fixed the problem.

[hskrsolara]

now...where can we find one (IAC) for the best deal? any hookups or good sites?

[SirThomas88]

lol looks like we are not the only one's, but yeah im planning on throwing on meth with 6psi as well. But i would really like to get this fixed before i actaully do it because i really dont want this happening when i get excited and decided to floor it lol

Yeah, I'm not sure what flooring it while this low idle and lean condition is occurring will do to your vehicle. Will it stay lean and wreck your engine? Or not? I have heard that applying a little pedal should fix it when the IAC is sticking, though that one time it was so bad my car almost stalled, gassing it didn't do a thing.

Hskrsolara, you don't happen to have a wide band AFR gauge do you? I notice my AFR tends to get very very lean when this happens. Something to keep in in mind.

yep, I do have an aem wideband. when this happens, my a/f jumps off the charts (red). LEAN. I'm getting an IAC asap!

Ah, well then indeed you do have the exact same issue as me. Does this happen frequently for you? And have you tried cleaning it out with Throttle Body Cleaner or MAF Cleaner?

[SirThomas88]

If you guys want to try cleaning your IAC, here I'll try to describe how to do it.

You need Throttle Body cleaner or MAF Cleaner. There are two ways of going about this, the easy way (might not clean it fully) or the hard way (preferred method, you can do a better job).

Easy way: Take off your intake to expose your TB and spray TB or MAF Cleaner down into that little hole in front of your butterfly valve.

Hard way: This involves removing the IAC from your TB. The IAC is the metal box screwed onto the bottom of your TB. It is attached via four phillips head screws. Three hoses run off of it. The middle is a vacuum line, the other two are coolant lines.The IAC also has a small plastic black box attached to it with two screws and has a wire plug running from it. The two screws on this black box are VERY EASY TO STRIP.

It might be possible to remove the IAC without taking off the Throttle Body. Disconnect the three vacuum lines and see if you can fit locking pliers around each of the four screws securing it to the TB. I suggest using locking pliers since you can get much better grip on the head of the screws without worrying about stripping them. If you can't get to those four screws with the TB still attached to your intake manifold, then remove the TB enough so you can twist it upside down.

Be very careful when removing the two screws that hold the black plastic box. I'd suggest ordering two replacement screws for it from your dealer if you're not confident you can get them off without stripping. For me, I barely got one off, and the other one stripped. I had to order two new screws and also purchase a screw remover kit. Those kits are great. They have reverse thread. They are essentially a drill bit with reversed thread that you screw into the stripped head of your screw. Worked great and did the trick for removing the remaining screw.

Once you've got the IAC off the car and the black box removed, you'll see the IAC is comprised of a moving part that turns about 60 degrees back and forth. There's a magnet on the end of it, and a spring that is inside the thing somewhere. Try rotating the magnet and see if it feels like it's sticking. Very liberally apply TB/MAF cleaner and wipe any dirt or corrosion off from the moving parts. Let it air dry and reassemble.


I'd be curious to see if this fixes the problem for you guys. So give it a shot! And let us know how it turns out. Better than spending $140 on a new IAC.