I was wondering if anyone else is having this problem or has a solution. When I step on the clutch for more than just shifting(breaking) the RPMs naturally drop down to idle and keep going to below the 550 or so to like 200-300. Once it even stalled(never happened before). Then it goes back up to normal, 550-575. The car idles fine then. It is very smooth, no vibrations. I was wondering if I have a sensor that is on the blink or something manual like the throttle cable is too tight and drops the RPMs too fast.??? Everything has been serviced within the last month or two; K&N air filter, Mobil 1, OEM Oil filter, Redline MT-90, Bosch Platinum +4s (no fuel filter yet, too cold) and I put 93 Octane in it. Anyone have any suggestions?

'98 SE 5-Speed Sterling Mist

 

You may have a sticking or broken IACV-AAC.
Here is a paragraph 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)

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!

 

All right I'll give that a try. Won't leave the a/c on too long though. It's supposed to be 20 degrees when I get out of work.

 

Do the test only after the engine (and you) are at normal operating temperature. It takes only two seconds. The idle speed will either
(1) dip and recover, or
(2) dip and fail to recover
in one or two seconds.

 

You can try boosting the amount of air your car gets at idle. There is a plastic screw on the throttle body. Try turning this counterclockwise some and see if that has an effect. It worked for me.

 

There are two considerations here: idle speed and idle stability. Turning the screw on the throttle body is the way to adjust idle speed. However, it will not address the problem of idle stability. That is handled by the IACV-AAC valve. I read TomJ's posting as an idle stability complaint.

 

You know, I had the same trouble about a week ago and
I cleaned the throttle body with fuel Injector cleaner.
After doing so, the idle never dropped below the normal
idle RPM when coming to a stop. Also, I notioced that
the idle remained higher (1K RPM) while approaching a
stop and once I came to a complete stop, it then dropped
down to the idle range.

While cleaning the throttle body, could this have cleaned
out the valve you were referring to? Let me know.

Pete M.

 

Possibly, but not likely. The IACV-AAC valve is fastened to the upper intake manifold about two inches downstream of the throttle body.

 

I tried the a/c test last night and it worked correctly. The RPMs dropped 50 for a split second, then went up 200 and then settled at 100 more than normal. So I guess the whatever valve is working correctly. Thanks for the advice though. I'll try the injector cleaner next. The car has 43K on it now so it could probably use some. I have heard it is not good to use it all the time(eats away at things) so I do not use it, but I'll try it here. My Mickey Mouse remedy was to keep the defroster on(keeps the RPMs at 900+/-).