Strange idle...

[carolinus]

My car has recently started to idle sort of strangely. When it is cold, it idles at 800 to 700, and is a little rough. When I use the gas pedal to bring it up to 900, it smooths out. It also gets a little better when the car warms up.

Should I monkey with the idle screw? Vacuum leak maybe?

What do you guys think?

Note: New spark plugs and wires, and some new vacuum lines in the fuel system.

[SoCal Driver]

Idle bypass/control valve. It's buried under the center of the intake manifold bolted to the block with a bent sheet metal bracket.

This is a blade or "knife" valve that is opened with a bimetallic spring and resistance heater element.

There are two larger diameter vacuum hoses going to and from it.

If you pull the electrical connection on it and check the pins on the valve you should see some resistance from the heating element. If you do then pull the top hose and squirt the heck out of it with carb cleaner followed by a penetrating spray.

If there is no resistance then the heating element has gone kaput and you need to replace it.

Note: The post 85.5 944's use a different designed valve. It is not interchangeable. The 944S's idle valve is different from the rest too!

[carolinus]

How do you recommend getting to it? Can you see it when you take off the intake boot?

[SoCal Driver]

Further back. Between the center two runners from the plenum to the intake ports on the head.

Might have to take off the throttle body to get to it.

[carolinus]

It just stopped doing it. How strange. I will give that a shot if it acts up again.

[todwic]

Originally posted by carolinus
It just stopped doing it. How strange. I will give that a shot if it acts up again.

Prolly had some crap in a line or something. If you want to check you
AAV, Stick it in the freezer for a few hrs. look inside and there should be holage. Heat it Let it warm up and the hole will get smaller. If you get it hot, Hole go bye bye.

[944S Boyeee]

SoCal - where is the S's idle valve and how do you adjust it? I heard the S doesn't have the infamous screw you can adjust on the N/A's.

944S Boyeee

[carolinus]

It is doing it again... Also, next to the AAV but closer to the radiator there is a sensor or something with one wire coming off of it. Engine temp sensor? This sensor and its associated wire and connector is absolutely soaked in oil and stuff. If it is engine temp, that might be part of the problem, yes? (Note: Will clean anyway, but...)

[SoCal Driver]

Originally posted by carolinus
It is doing it again... Also, next to the AAV but closer to the radiator there is a sensor or something with one wire coming off of it. Engine temp sensor? This sensor and its associated wire and connector is absolutely soaked in oil and stuff. If it is engine temp, that might be part of the problem, yes? (Note: Will clean anyway, but...)

The single wire sensor is for the gauge as Wilk's states. There may be sufficient wire to clip it short and re solder it to the clip. Yes use the clip that is on the end of it as while this looks like just another slip-on it's not.

Try to remove the top vacuum hose to the valve and do the carb cleaner and penetrating oil thing. Helps about half the time. However as old as our cars are replacing the valve is the better choice even if removing the intake is necessary.

[SoCal Driver]

Originally posted by 944S Boyeee
SoCal - where is the S's idle valve and how do you adjust it? I heard the S doesn't have the infamous screw you can adjust on the N/A's.

944S Boyeee

You have to jumper across two of the pins on the round test plug in the engine compartment to center the servo controlled idle bypass valve then adjust the idle at the throttle body.

Have to do a search on the subject to find out which of the two pins.

[carolinus]

Loud cursing now ensues! I decided to unplug the o2 sensor and determine if it needs replacement. The waterproof connector there broke right in half the second I tugged on it. I am now looking for the best options to replace it. Somebody said it was coaxial?