Idle hunting?

[scottb]

I had the identical problem. I replaced the ICV, the O-2 sensor, and the head temp sensor. Nothing helped. Then it was suggested that I have the mixture adjusted. I took the car to my friends at TRE and, voila, no more surging. Sometimes the simplest solutions are the best.

[Nine9six]

Scottb,
I followed kqw's procedure for setting the idle. If you read my previous post, you will see that attempting to adjust the idle speed, resulted in nothing. When I jumped per the instructions, the idle smoothed out but increased to about 1100 rpm.

[scottb]

Are mixture adjustment and idle adjustment the same thing? I was under the impression they were different. My bad.

[kqw]

It's a good sign that it's working...

With engine off, gGently lift up on the throttle and listen for a "click".
There is a micro switch under the throttle lever.

What I would do next is: remove the ICV, and clean it with carb spray etc.. the reinstall it.

With the engine running, test for vac. leaks on the manifold by spraying a little carb cleaner around the manifold intake. (where the manifold bolts to the top of your engine) There should be NO rise in engine speed or idle fluctuation.

If there is, re-torque those bolts to 18 ft/lbs. They are 8mm allen.

Check all the hose connections attached to the throttle body and throttle boot.

Quick check of the Cylinder Head Temp. Sensor by:

Just below the cruise control diaphram in the engine compartment, there is a bracket with 3 sensor connections.

The Top connection is for the CHT. With the engine running, disconnect that sensor and your engine should begin to race.

Did you mention when the last time you had the O2 sensor replaced. It is recommended at 30K mile intervals.

More to follow....

[Nine9six]

I dont believe so...Not your bad :-) More like your good.

[kqw]

The Idle and Air fuel mixture adjustments ARE different. Nine, which one are you adjusting?

[scottb]

My understanding is that the idle adjustment is mechanical, and that the mixture adjustment involves an analysis of exhaust gases.

[Nine9six]

kqw,
I have a photo that I took from a posting from Steve Wong, I hope to hell I'm messing with the idle adjustment per the photo from Steve.
Is it the idle adjustment that takes a 7mm socket, and has a little tit extending out from the center?

[rcaradimos]

I read a post that said there is an o ring on the idle screw that can go bad, and can create problems trying to ajust idle speed.

1. which way should increase idle, clock wise or counter?
2. can the screw be backed out counter clock wise to check o ring?
3. is there a rule of thumb, being turn clock wise till finger tight and turn counter clock wise so many full or half turns to be in the ball park?

Thanks
Bob

[kqw]

Nine...

yes, that the one in front of the throttle body....Whew....

Bob, Clock wise should close or drop the idle, counter should open up or increase idle.

With the jumper in place, set your idle to approx. 820 by looking at your tach.

Note: response to turns on the idle adjustment screw may be a few seconds delayed from you seeing a difference in idle.

Make sure car is at operating temps.

[kqw]

Sent you guys a PM..

[rcaradimos]

Fixed, took out idle screw, cleaned black crud off end of screw and out of inside throttle body, cleaned ISV put back together and tried to make idle ajustment, still no luck.
Noticed sound of air coming from idle screw while making ajustment, and if I put some pressure on screw from side to side it would change.
Removed idle screw inspected o-ring again an figured I would get a new one as it seems it was not sealing well, picked one up for .15 cents and noticed that it appears that there should be two on the idle screw, added the new one, and it looked right both side by side at top of screw, not together but in its own groove, installed.
Then I was able to ajust idle to 800/850 and its rock solid.
Need some good weather up here before I can get it out for a good run.
Has anyone else had such an easy fix?

[Nine9six]

Congratulations rcaradimos! Sounds like a good job of troubleshooting.

[rcaradimos]

Nine,
The missing o-ring was the problem, it might have just desinigrated over time? I know the pipe line that goes from back of throttle boot (metal with rubber conection at other end was dry rot with a good size crack on back side, front of rubber look like new was from age) was drawing in air creating vaccume leak. Good luck and check the o-ring on that screw.

[a911]

Could official porsche dealer find reason off idle hunting just by conecting it on computer? Or is it same checking as is on Haynes manual ( icv, vacum leak, airflow meter....)

[rcaradimos]

I think if you can rule out as many items as possible before bringing to a dealership you could save some dollars.

[rcaradimos]

What I understand is leave the air flow meter and co mix to the experts, the other items you should rule out.

[a911]

Here is the problem: "88" ROW carrera
If i rev engine to few thousand revs and release pedal quick, it picks up idle fine.
If i coming to a slow stop with engine breaking and slowly engaging clutch it starts hunting and sometimes even stall.
Its not heat related.
When ignition on icv is buzing.
I checked this with my very limited skill:
- checked mainfold bolts
- checked for vacum leakes
- Cleaned ICV and electricaly checked ( not sure bout electric part )
- cleaned and electrical check AFM
- checked idle switch

It hunts from 300 to 1300rpm. It even stalls sometime. If i help with a blip on throtle i can find steady idle.

[Nine9six]

a911,
When was the last time your o2 sensor was replaced? Oh BTW, you are welcome to piggyback your questions on any of my posts. I feel it keeps the post alive and generates more information. Some dont like it when others post their questions, in someone else's post, but as long as its related to the original question, please feel free.

[a911]

ROW carrera is without o2 sensor!

HUH you have a 996r?!!?!? gr8 bike!