Have a problem with the idle speed of my PS 7900. . I find it will not always stop when the ignition is switched to off. Any ideas on what the problem might be?

First, increase the idle speed. Easy/cheap to do
You should idle above 1000 rpm

Some makers used Vacuum releases for their emergency brakes which had a Vacuum switch connected to the shift assembly. This would account for a stumble if Vacuum vented out through this switch.

More common for shifting stumble to occur from Park to Drive, engaging a load on the engine, not to stumble to a freewheeling Park position. Sounds like idle speed control is sluggish to stabilize the motor.

You also have idle speed control problem with A/C, kind of shows that A/C was what kept the engine running because when you turned the A/C off, the car died.

I am going to give you some Websites for wiring diagrams. Alldatadiy.com amd Autozone.com with free wiring info upon registering your vehicle.

It seems that the base Idle speed control is not working and the A/C idle speed control is.

Also check for Vacuum leaks on the intake manifold by spraying water from a pumpbottle on the seams of the gaskets.

Check ignition Relay or ignition switch for random cutouts. The fusebox layout is on the Autozone site.

I hope my solution helps.

Some causes about rought idle could be:
- Valve adjustment
- Incorrect ignition timing,
- Vacuum leaks
- Bad ignition wires (Test w/ ohmmeter)
- Incorrect idle speed
- Cold Start Injector always "ON" (Revised injector time switch avail.)

A source of rough idle in EFI engines is air leaks or vacum leaks these leaks will upset the fuel mixture without triggering any codes. A bad oxigen sensor will also cause a rough idle, but you should see a code for it ( I think is number 5, but check it).

A good place to start would be an inspection of the spark plugs, plug wires, ignition timing, and idle speed. Next would be valve adjustment. Don't overlook the simple things.

Hope this helps, keep us updated and just keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa.

The engine fan is controlled by a relay and a radiator temperature switch.
Unplug the switch at the radiator, and if the fan still runs, the relay is stuck on.
If you unplug the relay, it should stop. If not, you did not pull correct relay.

Engine oil gauge is for pressure, not level. And pressure should always drop at idle speeds. As long as it is over 40 psi when at higher speeds, then oil should be ok. Normally at idle, the pressure will drop as low as 7 psi.

Sorry, not a solution but I think we have the same problem with photos only. When I tried it in movie mode, the movie was OK. Anyone have any ideas?

you need to replace the fuel sock in the tank and the fuel filte and do a tuneup wires plugs and cap.

almost sounds like a binding on the ignition switch.
if you have to lift up the gear lever to start then its not aligned right. The switch you need to replace it not where the key goes in but its located under the dash just above the drivers knee area, on the top of the steering column. A metal bar attaches from the key area to the center of this switch and my bet is the switch is worn out.

could be difficult this one as i dont have car in front of me,try changing the crank sensor.also look at wires on back of ignition switch for a loose connection in the first multiplug,did have a similar problem with old alberts one of these a diesel and it was the actual electrical contacts in the ignition switch.if removed and pushed down it worked .fitted a new recoditioned one from a scrap yard

this is usually due to a dirty throttle body. just beware if you do try to clean it you will need to preform the idle relearn procedure. this does work, ive done it personally.

A. Accelerator Pedal Release Position Learning Procedure.
1. Make sure that the accelerator pedal is fully released.
2. Turn ignition switch “ON” and wait at least 2 seconds.
3. Turn ignition switch “OFF” wait at least 10 seconds.
4. Turn ignition switch “ON” and wait at least 2 seconds.
5. Turn ignition switch “OFF” wait at least 10 seconds (how would you know if you get it right?)


B. Throttle Valve Closed Position Learning
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch is “ON”.
3. Turn ignition switch is “OFF” wait at least 10 seconds.
Make sure that the throttle valve moves during above 10 seconds by confirming the operating sound (i never get this right because i never heard anything)

C. Idle Air Volume Learning (Throttle Position Learning)
It's best to time with a watch/clock.
1. Perform “Accelerator Pedal Released Position Learning”.
2. Perform “Throttle Valve Closed Position Learning”.
3. Start engine and warm it up to normal operating temperature.
4. Turn ignition switch “OFF” and wait at least 10 seconds.
5. Conform that accelerator pedal is fully released, turn ignition switch “ON” and wait 3 seconds.
6. Repeat the following (steps 7a, 7b) procedures quickly five times within 5 seconds.
7a. Fully depress the accelerator pedal (HARD)
7b. Fully release the accelerator pedal.
8. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 20 seconds until the Check Engine Light (CEL) stops
blinking and turned ON.
9. Fully release the accelerator pedal within 3 seconds after the CEL is ON.
10. Start engine and let it idle.
11 Wait 20 seconds
12Rev up the engine two or three times and make sure the idle speed and ignition timing are within the specifications. (this is fine because SES light lets you know if you did it right the way it blinks)

GM Bypass Ignition System Operation part 1