Keaton944

My newly acquired 87 944 has low idle. I did some research and decided i would adjust the idle nut to see if that would help. I did the correct procedure, engine running, at temp, jumper on diagnostic port to disable stabilizer. I did about one full CCW turn and it barely made a difference. Although it did help, it raised it maybe another 100rpm, but im still about 150-200rpm too low of where i want to be. From past threads it seemed like 1 turn would be plenty. The guide on clarks just said to adjust until you reached the point you wanted. I stopped after my 1 full turn to come and ask for you guys opinion.

BTW, i went to look at my other 86 944NA, to see about where the idle screw was to compare, since it idles perfect and i love it. and to my surprise, there is no idle nut at all there, some yellow plastic thing with what looks like vent holes. So with nothing to compare to. what do y'all think? I guess my only fear is backing it out too much? is that a possibility?

Obviously i know there are other things that can cause the low idle such as TPS and ISV and i will check those when i have time but i was mostly puzzled as why a full turn on the idle nut barely made a difference in idle rpm.

Here is a pic of the yellow plastic thing on my silver 944 that has great idle. Any ideas what that is? What's "funny" about this whole thing is the red car with bad idle runs much stronger and smoother when racing through the gears than the silver car with great idle that sometimes has hesitation when racing through the gears.

Thanks,
Keaton

krystar

yea mine's about same. ~100rpm per full turn. just keep on turning till u get it where it needs to be. but u should probably question why it was that off to begin with.

Keaton944

it was a 944S converted to 944 NA 8 valve engine. then it sat for a while and the ECU, DME, fuel pressure regulator, along with some other stuff, was replaced to get it running again. I've inquired to the PO about if the low rpm was always a symptom is had since he got it or did it show up after replacing the DME and such recently to get it running. I haven't heard back from him yet but hes been great about answering all the questions i have had about the car. This will shed some light if it was something that wasnt addressed during the engine swap or if it is something to do with the DME or other component that was recently replaced.

when not at idle, she runs great. based on this i was certain the idle just needed adjustment, maybe i just need to adjust it some more.

anyone know what the yellow plastic vented thing is on my other car?

jcslocum

I think they yelloe thing is just a cap over the idle adjustment nut from the factory.Pop it off and you should see the nut/screw.

If I recall correctly, the idle adjustment is actually an air bypass so if it's capped to keep you from fooling with hit, it needs to be vented.

Keaton944

well i got the idle set adjusted up some more, much better although it took like another 2 turns or so which seemed kinda excessive, i was expecting a much sensitive response to turning the nut.

So i got a good idle now, even when going from in gear high rpm and dropping into neutral and idle it idles good and doesnt dip down and almost die. However, when i turn on the AC (not the air it doesnt bother it, but the AC) it drops the idle down a lot, where as on the silver car turning on the AC makes it dip a tiny bit but it comes back up in a second. On the red one when i turn on the AC i lose 400rpm or so. Is this an electrical drain problem, maybe with connections or the alternator? or is this a symptom of a idle stabilizer control gone bad?

other loads don't seem to bother it, headlights and etc, just the AC compressor.

Keaton944

just a bump to see if anyone has any ideas on why turning on the AC is still killing the idle RPMs.

Also, anyone know what size the nut is for the wire terminals on the oil pressure sending unit, the little tiny ones, is it 7mm? I tried to get it off with needle nose pliers but i cant get a good grip where its positioned.

Thanks,
Keaton

jcslocum

I think you are looking at the ISV replacement. I have been having trouble with cold start issues and it seems like this valve is involved with the cold start and the drop in RPM from the AC or other heavy electrical loads.

Check out this info. Read the info at the top of the page that discusses what the valve does.

Keaton944

that is what im suspecting. When i was doing the idle adjustments, and i did the jumper wire to disable the ISV, it was like nothing happened, i was kinda expecting the idle to drop more, but it seems to act the same with or without the jumper in place. so im guessing my ISV is dead, or bad connection.

is there a way to test the ISV like by checking with a multimeter at some connection at the DME computer? Similar to checking the TPS? Id like to prevent having to remove the fuel rail and intake manifold unless im sure that sucker needs replaced. but based on my symptoms it sounds like it does need replaced.

F18Rep

Do the easy stuff first... Here's what I would do... turn the idle adjustment (air valve) clockwise, counting the turns til it bottoms out. Keep that number in your head. remove the air valve completely and pull off the oring. Clean up the air valve, which is really just a brass screw with a wire wheel or whatever (i expect it will be coated with carbon or baked on oil sludge). Blow out the throtle body passages with compressed air. Put it back together (with the oring) and with an initial setting of two tiurns (or whatever) up from the bottomed out position. Now, adjust your idle per the book.

PS you can make the ISV open close with a 9v transistor battery - difficult to "see" it when installed but you may be able to hear it....Bruce

Grandpa#3

Hi Keaton, Go to the link below on how to test the ICV.

http://www.texasblake.com/porsche/tech/icv.html

Cheers,
Larry

Keaton944

thanks for all the advice guys, i love working on these cars and i couldn't do it without the help of this awesome community. now i just can't wait to get home and get to tinkering =)

jcslocum

Sorry for not putting in the link earlier

http://www.clarks-garage.com/shop-manual/fuel-21.htm