View Full Version : Idle problem resolved

04-11-2002, 12:02 AM
I didn't post anything on the forum about it, but with some searches, it looked to be a common enough problem to justify posting my recent experience..

Monday, on the way to work, about 5 minutes into the commute, the idle, obviously, started to falter. Dropping from 650-700rpm down to the 450rpm range, rebounding back up to 550-600 every so often. The choking sound of the exhaust (with a hole in it ;) ) added to the situation. Sounded as if I had "lumpy-*** racing cams", frankly. :cool: Hardly..

On goes the A/C, which kept the engine just under 1000rpm and therefore a 'tolerable' idle.

Needless to say, this would not do. It was too cold! ;)

Once I was able to search around the forums, 240sx.org, and google (at work, muahaha). I settled on the IAA unit being at fault (Idle Air Adjusting Unit) and/or the AAC valve (Auxiliary Air Control Valve) (FSM: page EF&EC-12).

Initial physical troubleshooting consisted of cutting battery power, hence resetting the ECU. With the car idling in the drive way, everything was fine for several minutes upon end. Long enough for me to turn off the engine with satisfaction.. Taking the car out for a short test drive, however, in no more than 100ft <25mph, the problem was back. The sequence was entirely reproducible.

I removed the IAA [4 easy bolts, #10 wrench/socket accessible] and opened it up. It was pretty dirty.. far from 'clean'. There where small deposits of fuel/fine dirt on the inside walls and who-knows-what on the inside. With some engine degreaser [didn't have anything decent to soak/submerge it in] sprayed in/on the appropriate surfaces and a few minutes of waiting, some water from the hose to rinse it out, and it was looking better. I let it dry/drain for as long as I could [overnight] and then put it right back in place.

The car started up, I took it out for ~10 miles of city driving and everything was normal. Later that evening again, took it out for ~40 miles of 'spirited' driving. High revving in general, up to 110mph in one area if that matters

The car ['89, KA24E, 130k miles] is performance-wise completely stock. Only thing different might be that the air filter is being held up with fishing line, therefore, no 'air box' [and no genuine 'cold-air-intake']. The check engine light, regarding leaking injectors [ECU 45], was/has been on for some time, ~1500miles if I had to guess. Granted, I could see/smell the injectors leaking long before.

If anything was to be suspect, it would be the condition of my old paper air filter... which I'm sure is long overdue. The air box has been off for maybe ~2000 miles.

[Hm.. First time I actually had to 'debug' my post.. UBB spewed errors when I had over a certain amount of parenthesis in some places]

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04-12-2002, 01:11 AM
so was it the IAA valve??? post is unclear and not finished it seems

04-12-2002, 08:10 AM
yup thats what it was!!!

04-12-2002, 10:25 AM
Best bet for cleaning idle air control valves of various flavors is to use some carb cleaner. Spray the guts of the valve out with the carb cleaner, and maybe spray some WD-40 in there to lubricate it. You can also, optionally, hook 12v and ground up to the motor and click the valve back and forth a few times to free it up. Don't keep the juice on the valve for a long time, just tap it on and off a few times.

You can quickly do this, reinstall the valve, and be back in business - carb cleaner and WD-40 are combustion friendly, and don't mind being in there http://www.freshalloy.com/ .