all sorts of not right idle

gearhead290 · 08-31-2003, 08:44 PM

What is causing it? It idles at a bunch of different places. Sometimes it's 1200, sometimes it's 1300, soemtimes it's 1400 and so on. It doesn't ever idles much over 1500. On occasion it'll get stuck at 2000 (usually after getting off the highway). Any ideas?

Scott R · Scott R's Garage

Vacuum leak, somewhere..... How is your "J-boot" any cracks? How is the movement of the AFM barn door? Mine would run fine on the highway then it would be stuck at high ilde when I got off the freeway. It was a bad AFM spring.

gearhead290 · 08-31-2003, 10:09 PM

J-boot is fine (I replaced all bad lines and what not when I put the engine in). How do I check the AFM spring??? Just take the intake off or what?

Scott R · Scott R's Garage

Yea, just remove the boot and check the action on the "barn door" it should be smoothe.

If you have done all of the hoses and such, you may want to start checking sensors like the DME temp and throttle switch.

Porsche944 · 09-01-2003, 04:01 PM

Perhaps the throttle plate mechanical stop, or the Throttle Position Switch are not adjusted properly?

To check this you need to remove the throttle body, loosen the TPS screws, loosen the lock nut on the mechanical stop screw, and then back the stop screw out until it does not touch the stop arm.

At this point the throttle plate should be fully closed. HINT: This is a very good opportunity to give the TB a good cleaning.

Check the return spring to make sure the throttle plate will go fully closed. Once you have verified this, turn the stop screw in until it just touches the stop arm. Turn the stop screw in an additional 1/2 turn and then tighten the lock nut. The mechanical stop is now set.

To set the TPS, hold the throttle plate closed and turn the TPS until you hear it click. Tighten ONE of the screws and test the TPS several times, verifying that the switch clicks just as the throttle plate comes off of the seat. Once this is verified, tighten the other screw and reinstall the TB.

Now you need to set the mechanical idle. To do this put a jumper wire between pins B and C at the diagnostic plug on the driver side fender, and connect a dwell/tach to the primary (green) wire on the coil. Start the engine, let it warm up, and adjust the idle by-pass screw for an idle of 840 +- 50 RPM. Remove the jumper from the diagnostic plug.

Have a cold one.