High Idle at start

[JINKATIN]

Hello, everyone
I recently replaced the cylinder head temp. sensor on my 86 Carrera. Everytime I start it, it idles at 1100-1200 and stays that high for about 5+ minutes. I wanted to know if this has this happened to anyone and if so how was it resolved. I am wondering if I did not install it properly. Can anyone please help?

Thank you,

jinkatin
86 911 Carrera

[DRACO A5OG]

Hey JinKatin,

Check the Idle Control Valve (ICV) buy tapping on it with a screw driver while she idles at 11-1200 RPMs. If she settles down, your ICV needs cleaning. ALso check the OHMs with a DVM should be 20 at center and a outer terminal. 40 on outers.

Jim

[JINKATIN]

I will do that, thank you Draco I really do appreciate your help


jinkatin
86 911 Carrera

[DRACO A5OG]

No Problem Brother, if you need any help let me know I'm in L.A.

RSD,

Jim

[dshepp806]

Why was the CHT changed to begin with? Was anything symptomatic?

Best,

Doyle

[JINKATIN]

My car was having Idling problems, loss of power issues, black soot being left on my rear bumper from exhaust. After I replaced the CHT, no more black soot, no loss of power issues, but now the Idling problem is worse. I tried what Draco advised me to do, tapping to ICV while it is idling at 1100-1200 RPMS. The car was still idling at 1100, but do not have a DVM so I did not check it.

Thank you,

Jinkatin
86 911 Carrera

[JINKATIN]

Im sorry for this stupid question but,
How do you clean an ICV and what do you use to clean it with?


Thanks,

Jinkatin
86 911 Carrera

[DRACO A5OG]

A search will give you a more detailed steps but here it is in a nut shell:

Remove ICV, twist shake the ICV for non-binding movement and then clean internals with carb cleaner until fluid comes out clear. Finish with some spray lube (not WD40).

Check the OHM's and replace

[JINKATIN]

Draco, Once again thank you


Jinkatin
86 911 Carrera

[glennspiegler]

There is also an idle control switch behind the throttle linkage at the throttle body. With 1mm of linkage movement you should hear a click, off the throttle and click again. Can also disconnect it at the plug to the right of the throttle body, above the full throttle switch and check it with an ohm meter when the linkage moves the 1st mm. Bentley describes it well.

[JINKATIN]

thanks, glenn I will do that.


Jinkatin
86 911 Carrera

[sig_a]

Idle 1100/1200 rpm range when first started is normal. Then slowly slips down to about 850 rpm. Colder the engine, longer it takes to idle down.

[DRACO A5OG]

Originally Posted by sig_a

Idle 1100/1200 rpm range when first started is normal. Then slowly slips down to about 850 rpm. Colder the engine, longer it takes to idle down.

True, but he is in SoCal and it should drop after 45 seconds

[DRACO A5OG]

I just red the Bentley Manual, you may want to check the "IDLE POSITION SWITCH" located on top of the Full Throttle Switch. It is a two terminal connection.

Run the engine, and pull the plug and your RPMs should jump 500 RPMs, if not it may be defective.

[JINKATIN]

Draco, you are awesome. I will do that.

Thank you,

Jinkatin
86 911 Carrera

[glennspiegler]

That's the switch I was referencing. Idle is the 2 prong plug and the full throttle switch is the 3 prong. Put your ohm meter on the two prong idle switch and while moving the throttle manually, you should see the meter go from continuity to no continuity after the first millimeter of travel which is when the switch will "click". Then it should click again when you release the throttle and the ohms go to continuity again. Good luck. I just did this in prep for my Steve Wong chip which is in the mail. It was Steve's idea for me to check this switch. My full throttle switch was not working and I never new it. I opened it, cleaned contacts and 20hp return as per Steve. Tricky to open, but thats another post.

[dshepp806]

after the cleaning/lube,..you may want to revisit your idle adjustment for the ICV,..get you CO measurements....make sure the AFM's doing it's job . I took mine apart and cleaned the contact trace areas, resulting in a noted improvement at specific spots. Starting with the ICV cleaning is step one (as indicated by others...).

As to the switch,..Draco's dead on with "measuring" the switching event ,..forget "listening" for the click....measure it....


you'll get it.

Best,

Doyle

[JINKATIN]

Thanks, I truelly do appreciate all the help you guys have given me.


Thank you,

Jinkatin
86 911 Carrera

[BRP83SC]

Originally Posted by dshepp806

Why was the CHT changed to begin with? Was anything symptomatic?

Best,

Doyle

Don't mean to dumb down the post but what does CHT stand for?

[JINKATIN]

No worries, I do the same thing.
CHT stands for: Cylinder Head Temperature Sensor


Jinkatin
86 911 Carrera