[Jamie '92 968]

Flash et al.,

My throttle cable is good (actually a bit loose, so I tightened it up).
I adjusted the screw under the arm stop (only about 1/2 turn).

After adjusting, the idle appears unchanged. Maybe I haven't made a big enough adjustment.
I'd give it another turn, but I also notice that the accelerator now tends to stick a bit at zero position (fully released).
My theory is that the screw adjustment allows the valve to close too far so that it is sticking. I'd have to do some disassembly to confirm.

Is it possible that my high idle (950 RPM) is an indicator of something else? A bad temp sensor perhaps?

Maybe I'll get a chance to hit it with the Bosch Hammer this weekend at RSB to try to diagnose...

Jamie

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[kwikt]

Correct me if I'm wrong but the butterfly set screw will not adjust the idle. The idle speed is regulated by the ICV and TPS through the DME. I tried also adjusting the set screw once with no change in rpm. So I backed out the srew til the butterfly was closed then tighted it a 1/2 turn. Otherwise the butterfly would seem to stick at the closed position.

Kevin

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[flash]

sort of

the screw is a stop for the throttle arm - it is supposed to establish the minimum opening of the throttle body at idle, and set the "zero" condition for the sensors

the position of the throttle arm dictates the readings the sensors get - so, adjusting that screw will adjust the idle - it won't go below the lower limit of the sensors though - but if you adjust it so that it starts moving the throttle arm, it will raise the idle

if it is already set too high, backing it off will lower the idle back down

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[968 GUY]

[size="2"][/size] Maybe you could disconnect the batt. and it would re-zero the sensors???

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[RS Barn]

Jamie,
We can check throttle angle with Hammer. Should be close to 0 degrees. We can also check signal from TPS and voltage. Should be .5V or so.
If it's out of range idle can be out of range.
We're getting so blinkin smart...
That doesn't mean we'll fix though
Pete

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[Jamie '92 968]

Pete,

Sounds great. I can't wait for Saturday. Thanks for hosting!

Idling at 950 doesn't seem to be bad, just slightly out of spec. I can't complain for a 17 year old car with over 140K miles. For me it's more of a curiosity thing to understand why it's happening.
Every time I ask a question like this I learn more about the car. I love this forum and the great people who make it so valuable.

I'm thinking that perhaps the high idle could be caused by a vacuum leak if not some sensor error. Looking forward to learning more on Saturday!

Jamie

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[Jamie '92 968]

So it took Max about 10 seconds to diagnose my high idle problem.
Turns out that according to the Bosch Hammer, my idle is a perfect 840 on the nose.
My tachometer must be off.

Thanks again RS Barn. [img]style_emoticons/<#EMO_DIR#>/smile.gif[/img]

Jamie

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[Rogier1975]

[quote name='Johannvb' timestamp='1257620117' post='82904']Jamie, I used a 1/4 inch socket set, with a number 10 socket. But since there is so little room to move down there, I just loosened the nut with the socket and then did the rest by hand. If you take the socket of the ratchet you can use the socket on its own, and this will stop you from dropping the nut down the engine compartment. Good luck! Oh, yes....My muscles are aching today. This job is like playing twister with your car[/quote]



And AMEN!

Just used a rather short 10mm combination wrench to get to this nut. The first one appeared to be gone for a long time, by the way - so I really needed to unscrew and screw this one remaining nut nice and gently. Also getting the ICV with the short hose/pipe back to the inlet manifold was tricky. In the end I first put back the short hose, then the ICV itself - was easier to manoeuvre for my hands at least. Did not have the CRC <acronym title='mass air flow'>MAF</acronym> cleaner yet, so only did the ICV for now (but <acronym title='mass air flow'>MAF</acronym> is far easier to remove & replace). Removing loads of tacky black gum from the ICV seemed to make a difference already: my (cold) idle rpm seemed after a minute or so already more stable than before, ~1050 rpm. Hopefully tomorrow time for a decent test drive to see:

a. If the engine does not stall anymore the first minutes when stopping (engine dropping below minimum rpm and stalling, only restarts with quite some gas applied)

b. The warm idle is also more stable



THANKS for this DIY guide!



EDIT: also replaced spark plugs, cap and rotor today - but that still resulted in a bit 50-100 rpm hunting idle.

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[Cloud9...68]

I've heard that idle stability problems on these cars can be caused by corrosion of the distributor mounts, which are in two halves which are held together by three M6 bolts. My mounts weren't visibly corroded, but the threads were in pretty bad shape, so I inserted heli coils in all three. Much more secure now. I'll see if this improves the quality of my idle once I get the engine back in the car and fired up.

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[surfer51]

compliments of 968 Forums member <b>Johannvb</b>



Idle_Con...ve_DIY_2.pdf

thank you for that info very much

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