Van

There may be too many causes for this problem to get a simple answer on, but I'll try it anyway. My car suddenly started dying on me this morning. It was fine yesterday. I did replace my intake 2 months ago and messed up my MAF sensor, but I went back to the original intake and repaired the MAF sensor. Everything has been fine for 2 months now. Now it's idling very low and keeps dying at intersections. I know how to increase idle, but I imagine there is an underlying cause to the problem and it's just the symptom of a sensor that's gone out, or a vacuum leak or something. Can anyone comment on this, or are there too many variables to answer without seeing the car?

Thanks,
Van

Daniel B. Martin

Here is some text copied from the factory service manual.

"Idle Air Control Valve (IACV) -- Auxiliary Air Control (AAC) Valve

This system automatically controls engine idle speed to a specified level.
Idle speed is controlled through fine adjustment of the amount of air which
by-passes the throttle valve via the IACV-AAC valve. The IACV-AAC valve
changes the opening of the air by-pass passage to control the amount of
auxiliary air. ... "

You may make a quick test of your IACV-AAC in the following way. With the
motor at normal operating temperature, and at idle, switch the A/C from
"off" to "maximum". Keep your eye on the tachometer as you do this. The
idle speed should dip momentarily and then recover. If it does this, the
IACV-AAC is working. If the idle drops and does not recover, the engine
may stumble, falter, and stall. The IACV-AAC may require cleaning,
adjustment, or replacement.

The correct idle speed is...
- 700 +/- 50 (automatic transmission, in Neutral)
- 625 +/- 50 (5-speed)

Here's the factory service manual component inspection procedure for the IACV-AAC.

1) Make this test with the ignition key OFF. Disconnect the IACV-AAC valve harness connector.

2) Looking into the valve connector with the latch at the top, you will see two rows with three terminal positions in each. They are numbered 1-3 (top row, right to left) and 4-6 (bottom row, right to left). Check resistance between the following terminals.
2 and 1.
2 and 3.
5 and 4.
5 and 6.
At a temperature of 68 F, the reading for all measurements should be approximately 30 ohms.

3) Reconnect the IACV-AAC valve harness connector.

4) Remove the idle air adjusting unit assembly (IACV-AAC valve is built-in) from engine. The IACV-AAC valve harness connector should remain connected.

5) Turn ignition switch ON and OFF, and verify that the IACV-AAC valve shaft smoothly moves forward and backward. If NG, replace the IACV-AAC valve.


There are other engine parts which play a role in maintaining the right idle
speed, but the IACV-AAC is the first thing to look at. Good luck!

Van

Daniel,

Thanks very much for your response. I just went out and checked the car. When I turn on the A/C, the idle dips, and then returns to around 800 rpm. Right now it seems to be fine. I then turned on the A/C, turned on the headlights on bright, turned on the wipers and radio on, put the car in Drive and held the brake down, and the idle was at 600rpm. I think that's about normal from past experience. It seems to be an intermittent problem, but from all indications, the IACV-AAC valve is functioning properly, unless it has an intermittent problem. I'll just have to keep an eye on it. Thanks again for your response.

Van