Idling at 2000 rpms

[s13conv]

I have an 89 240sx that was sitting for about 2 years. I put a manual tranny and ECU in it, replaced the fuel filter, air filter, PCV valve, plugs, and wires.

It was running great (for abour 3 months). Now it wants to idle at 2000rpms. And when driving at a steady RPM, it seems like it cuts out or surges.

When it's cold, it starts up to about 1800rpms, then goes down to 1100rpms and then as soon as it warms up (coolant needle around half), it goes right to 2000rpms and stays there. :-/

I checked the ecu and it gave a code of 55 no malfunction.

I've also cleaned the AIV, and put some carb cleaner through the 1/2" hose that leads to the air valve and IAA.

Is there a "more often than not" cause or solution? The car has 95k miles on it.

[s13conv]

This morning it was idling around 2400rpms!

[s13conv]

I cleaned the IAA valve and the piece it attaches to. I'm also going to reset the ECU.

[krakadil]

I had the same problem on my '90. I'm not sure if the cause of the problem would be the same, but mine had major vacuum leaks. I couldn't find any myself, so I had to take it to a shop to fix it. It took them the whole day to find them too. Take a look at the hose that connects your throttle chamber to the rest of the intake piping, that is usually cracked on the older cars. Also check the charcoal canister for leaks, especially if your car was in an accident like mine was.

Then again, it could be something completely different. I guess you can start checking out the vacuum leaks first.

[krakadil]

Oh yeah, mine was sitting for about two years before I bought it too. I don't know if that has anything to do with it or not.

[s13conv]

Thanks.
I'm beginning to think a vacuum leak too. I put a new Bosch O2 sensor on and replace the distributor cap and rotor (because I hadn't). It still idles around 2000rpms.

There are quite a few vacuum lines too.

[Mr. Spool]

did you find out what it was if so what was it.

[idlafie]

Sounds like your idle is WAYYY to high...when was the last time you had a tune up performed on your car??

Have you tried checking your timing with a timing light to see if it's at 15 degrees?? 89-90's should be at 15 degrees

Readjust your idle down to 700 (+/- 50 rpm) - this is done by disconnecting the throttle position sensor harness located directly above & to the front of the throttle body intake. It's a three wire harness...black/white/green wires. Once the throttle position sensor harness is disconnected, then you should be able to set the idle with the idle speed adjusting screw located on the passenger side of the engine towards the rear of the intake manifold. Look for a phillips head screw by the AAIV valve.

Try cleaning and re-greasing (with dielectric grease) the following two connectors/harnesses. a). Engine Coolant Temperature Sensor & b). Mass Air Flow Sensor. A faulty signal from these two wiring harness/sensors will cause your idle to fluctuate.

Hopefully that will solve your problems...Good luck
ID

[s13conv]

When I unplug the AAC valve it idles perfectly. For the last few days, I've just left it unplugged. The only catch is that when the engine is cold it doesn't idle high to warm it up.