Is anyone having an idle irregularity? I have to talked to three or four 240sx owners and all seem to have idle problems, and each has their own theory as to what it is.

John Thomas Capo
[email protected]


Most 240sx's eventually have a problem idling. This is related to the IAA valve which control the air mixture during idle. The two options to fix this are to have a dealer adjust the valve or simply have it replaced.

The symptoms are clear: as you hit the clutch or lay off the gas and the car begins to slow and idle the RPMs may drop (sometimes quite rapidly) to extremely low levels, sometimes actually stalling completely. If this is happening have someone check out your IAA valve and you may wish to clean all the ground wire connections for the car's ignition and injection system.

I hope this helps.

Chris L.
'90 240sx 143k

Another Question

My 1990 240 would shake terribly at idle and would have significantly less power. After 4 days the NISSAN dealer could not find anything. I have no idea what it could be. My accelerator was also sticking. Could that be it?


The accelerator is it. The throttle plate is dirty causing the stick. Go to the local auto parts store and buy some carb cleaner which costs about $0.99. Remove the air duct and open the plate and spray on both sides. Clean with a dry cloth and clean as far in as you can. It might help to clean the plastic air tube also with the cleaner. This worked wonders on my 240SX. It runs like new now. It should solve the idle problem if you have checked everything else. And the power will be where it should be.

Pete Atilano
Email: [email protected]

Another POV

I have a 1991 240SX. I had this idle irregularity problem and took the car to the dealer after I saved some enough money. After several hours of head-scratching, they figured out the IAA valve (which controls the air intake to the fuel injector) was the problem. All they did was to establish an extra grounding wire and also covered the original connecting cable with plastic tape to secure the proper grounding. Now I don't have to fix my eyes to the tachometer each time I press the clutch pedal. It was a really irritating experience and cost about $120, which I think worth it.

Temel Tirkes
[email protected]


And Another

1990 240sx:

Idled like crap for three months, finally fixed it last night.

Not only bad Idle but also ran rich, stalled, bogged down,... every bad habit you can think of. To make matters worse, sucked down fuel like an M1 Battle Tank $ !!!

Over past couple months started with the usual suspects; O2 sensor, plugs, wires, dist cap, rotor, air filter...marginal improvement, but definitely still crappy.

What the hell can it be?

Cleaned AIV.........Bingo!

Purrs like a kitten.

Hope this helps someone someday

edward h lopez - [email protected]



92' 240SX 5 speed
My idle RPM varied from 400 to 1500 day to day. Also the engine would surge slightly at 30 mph in 4th. Tried all the usual items particularly the AAI valve, but found the spade connector to the coolant sensor (there are two, its the one with only one connection) to be corroded. After cleaning the connection car ran fine. This may not be the fix in all cases but is very easy to check.