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toolapcfan · Mar 28th, 2003, 07:03 PM

I didn't think removing the AAC was all that bad, I took mine out, cleaned it up, tested the solenoids (there's two, one is the AAC and one is the FICD) and put it back in. Didn't solve shit. Thought my IACV-Air Regulator might be it so I checked it out and it's ok. I'm back to thinking it's my AAC since since unlplugging it has no effect on the car. Although the solenoid works if it isn't being told what to do, it can't do it. Here's some diagnostic processes you can try. I needed to type it up for use in the garage so you might as well have it as well.

Unstable Idle

1. Check EGR valve for sticking.
2. Perform Power Balance Test
When disconnecting each injector harness connector one at a time, is there any cylinder which does not produce a momentary engine speed drop? If not got to step 6.
3. Check Injector
Does each injector make an operating sound at idle? IF N.G. check injectors and circuits.
4. Check ignition spark
If N.G. check coil, power transistor and circuits EF&EC 84.
5. Check spark plugs
6. Check fuel pressure (after filter depicted)
a. Release fuel pressure to zero (refer to EF&EC 191) To do this, merely take out the fuel pump fuse, and start the car and let it run until it dies. Then crank the engine a few times to release the pressure. Put the fuse back in, connect the fuel pressure gauge. Pressure should be 36 psi at idle. If N.G> check pump and circuit.
7. Check O2.
a.Set "Heated oxygen sensor monitor" in Diagnostic Test Mode II. (EF&EC 50) Turn ignition switch to on. Turn ECU test mode selector fully right, wait at least 2 seconds, turn selector fully left, start engine and let engine warm up until coolant temp is in the middle of the gauge. Run engine at 2K for 2 minutes.
b. Maintain 2K rpm and check to see if red ECU led or malfunction indicator lamp goes on and off more than 5 times during 10 seconds.
8. Check for intake air leak.
Pinch PCV hose, does engine speed rise? If so there is a leak.
9. Check IAC screw for clogging. Disconnect TPS and try to set idle to 750 +/- 50 RPM. If N.G. check for IAS clogging or throttle valve clogging.
10. Check compression pressure.
Standard 178 psi, minimum 149psi with a amx of 14 psi difference between each cylinder.
11. Check ECU harness.
11a. Check ECU power supply and ground circuit (EF&EC 73).
12. Try a known good ECU.

Engine Stalls after Decelerating

1. Check IACV-AAC valve.
When disconnecting IACV-AAC valve harness connector, does the engine speed drop? If N.G. check IACV-AAC valve and circuit (EF&EC 121).
2. Check IAC screw for clogging. Disconnect TPS and try to set idle to 750 +/- 50 RPM. If N.G. check for IAS clogging or throttle valve clogging.
3. Start at step 2 in the Unstable Idle diagnostics.

Lack of Power and Stumble.

Follow steps 6 and 8 in the Unstable Idle diagnostics.