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Discussion Starter #1 (Edited)
Hey everyone. This Monday I bought a very clean '01 MR2 - fully loaded with black leather and 95k miles. Despite a week of gray, rainy weather here in Houston, I've loved every second behind the wheel. It looks great, handles phenomenally and seems to be getting incredible gas mileage (126 miles with the gauge on 3/4 tank so far). The oil is clean and the level is fine (I read about the 1ZZ-FED horror stories).

I noticed one minor issue during the first day. The idle hunts a bit and becomes a little rough for a few seconds, then subsides. This happens with the AC compressor on or off. The RPMs fluctuate randomly between 650 and 750 rpm at slow intervals - never below that, never seems like it will stall out. No CEL. Is this likely a dirty MAF? Anything else I should check?

Above idle there is no hesitation and the engine revs very smoothly.
 

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Is the weather network correct? Houston is in the 70's right now? So it's not for lack of warm weather. I've noticed my idle bounce a little, usually when the engine's cold... never been an issue. Welcome to the forum. :)
 

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Discussion Starter #4
Is the weather network correct? Houston is in the 70's right now? So it's not for lack of warm weather. I've noticed my idle bounce a little, usually when the engine's cold... never been an issue. Welcome to the forum. :)
Thanks! Yeah it's been warm and wet all week. Pretty nasty. I bought a can of MAF cleaner this evening - I'll give it a shot tomorrow and see what it does. It will be sitting at stop light, idling smoothly and then suddenly start shuddering. It's a bit unsettling coming from a Maxima with a silky VQ30DE.
 

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Discussion Starter #6
Thanks for all the help, guys.

Today I disconnected the (+) battery terminal, removed the MAF sensor and gave it a liberal spray with CRC MAF cleaner. Put it back in, reconnected the battery, reset the clock/radio/etc.

It didn't seem to change much. The car idles at an indicated 750 RPM (slightly higher with the AC compressor on) but still has moments where it becomes rougher with no visible RPM drop. Perhaps I'm being too sensitive - it is a four cylinder, after all.

Here is an audio recording taken with my iPhone of the engine with the cover propped up. Does everything sound alright?

20120204 150908.m4a - 0.06MB
 

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I couldn't see/hear your clip but once warmed up my car's idle often seems to come dangerously close to stalling at stops but it never does. I think it's just part of how the car was designed to keep emissions as low as possible.

a quick tip - next time you need to reset the ECU for any reason, no need to unhook the battery. Just open the fuse box (in the engine compartment, driver's side towards the back behind the battery) and pull and replace the 15A fuse for EFI1. Legend is inside the fuse box lid. That way no need to reset the clock, radio, etc.
 

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Discussion Starter #8
Keep in mind, this car has been sitting on a dealer lot for a month. I think the next step would be cleaning the throttle body. Any guides on here covering the procedure?
 

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Discussion Starter #9
Hey guys, I'm pretty sure I have a gunked-up IAC. I started the car on a cold day this weekend and the RPMs immediately fell to about 500, nearly stalling. I gave it some gas and it was fine afterwards. Today I started it and the RPMs drifted from 1200 to 1700 with no real rhyme or reason. When warmed up, RPMs will drift between 900 and 600 and the engine will sound really rough and nasty when the revs drop... like an old diesel. Yuck.

Any advice on cleaning it? Would carb cleaner do the trick? Can I use any of my MAF cleaner?
 

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I'd look at the PCV or a vacuum leak. The recycle goes through the IAC. Any loss of pressure from the vac system would effect the idle.

If you do end up needing to get to the IAC, its pretty easy to get to from underneath the car, its on the bottom of the throttlebody. If you remove it you're gonna need a new gasket for it.
 

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Discussion Starter #11
I'd look at the PCV or a vacuum leak. The recycle goes through the IAC. Any loss of pressure from the vac system would effect the idle.

If you do end up needing to get to the IAC, its pretty easy to get to from underneath the car, its on the bottom of the throttlebody. If you remove it you're gonna need a new gasket for it.
I'll check for this. Any harm in disconnecting the IAC to see if my idle stabilizes? Should I disconnect it with the engine running or off?
 

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Discussion Starter #12
Quick update:

Took it to Sterling McCall Toyota - they couldn't find anything wrong during their inspection besides a slightly low battery voltage. Odd, considering I've driven the car 40 miles per day for the past month. No CEL -> No codes -> No idea without taking everything apart, so the tech said.

The tech recommended running a bottle of Techron through the next tank. After reading the numerous positive reviews of this stuff, it may be just the ticket for my intermittent idle shudders. Still have 300 miles left on this tank before I can test this stuff though. I've been getting 33-34 mpg so far - very impressed.
 
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