mazdaverx7

on my early 85 i'm wondering how to adjst the idle and how to diagnose a high idle. my idle is a constant 1200rpm. its at 1200rpm on first cold start on, never drops or fluctuates. i have checked and have no vacuum leaks. the throttle cable seems fine and does not appear too tight. i have not cleaned the IACV or checked it. how do i adjust the idle and what things can cause a steady non fluctuating high idle?

mazdaverx7

went through the haynes manual and it said that it wasn't adjustable. i don't buy it. time to scrap that thing and pick up and oem Porsche shop manual

John_AZ

You might check a few fixes on Clarks-Garage.

One is the TPS-throttle position switch:
http://www.clarks-garage.com/shop-manual/fuel-06.htm

He has a few other areas to check.

It could also be a bad DME temp sender that is giving a constant "cold" signal to the DME computer. A cold signal increases the fuel to rich until the engine is warmed up.

Clean all the electrical connections on top of the engine as well.

GL
John

mazdaverx7

the engine does run fairly rich..which could be a faulty DME temp sender.. i'll have to look into that, thank you!

jcslocum

It's adjustable, you just need to pop the plug out that is blocking access to the screw. I don't have a pic to show you but if you search, you will find it.

mazdaverx7

i saw the plug on top of the idle adjustment screw.. looks very strange and out of place. but its discoloration matches the discoloration of other components so i think its factory..

Cochezz

If the idle is to high and no one has adjusted anythinkg you may have a small vacuum leak.

Other than that just adjust the screw on the throttle body that controlls where the throttle plate stops.

It wond take much to change the RPM's by 200 or so.

mazdaverx7

i'll tamper with it and see what i can get with minor adjestments. i don't believe i have any vacuum leaks, i hear no hissing and the idle doesn't fluctuate and i still have good throttle response. but i'll double check everything when i'm in there. i'll post a pic of that funny cap bolt that's over the idle adjustment screw.

mazdaverx7

here's a pic of the strange looking idle adjustment screw/bolt or cap:

ZR8ED

Yup. Turn that. Not much. An 1/8 of a turn will be noticeable.

mazdaverx7

turned it and its all the way closed.. idle is still about 1100rpm. i have a dme sensor from a later model 944..but truely believe i have the entire head from a later 944. with that said, since the DME sensor for the early build or pre 85.5 is a one wire and the one i have is a two wire, i am only using one of the two pins. temp gauge works perfectly fine. if i switch the connector to the other pin on the DME sensor, the temp gauge does not work. so i made a nice ground wire and grounded the other pin on the DME sensor thinking that the sensor was not internally grounded. still have a high idle.. anyone have any ideas?

zerMATT951

You may have a vacuum leak at the TB - that can let more air in just like the idle adjust screw does. I recently rebuilt the TB on my 951, it was a little tedious, but not complicated at all. I highly recommend rebuilding it if there is a NA kit available.

pjburges

Posche manuals available at cannell.co.uk
If you have an ohmmeter you can check for proper resistance at the dme plug
At the back of the dme computer eliminating the guess work!

mazdaverx7

idle is still high..about 1200rpm.. doesn't seem like the throttle body has an internal vacuum leak but i guess its possible. does the early 944 have an idle stabilizer valve?

krystar

yes it does. it's underneath yer Jboot/intake manifold.

u sure u don't have a vacuum leak? do this test. start the car, take out the oil dipstick. the idle should change. if it doesn't, then that means u already had a vaccuum leak before.