NA 944/1 Idle dip and slightly fumbling acceleration

[PDX-944]

So im hoping these are related, and that i can solve them!
First off, at cold start, it vibrates quite a bit at idle. idles about 8-900 (same cold or hot). is it supposed to idle higher when cold? why isnt it if so?

any time i push the clutch in, the idle dips a little then settles. its not that bad, but it shouldnt.

the fumbling i only notice when i really step on it, say WOT or less. i suppose i might notice it at constant speed, but its hard to tell if its little bumps i feel or slight bouncing in speed. its most noticeable when i really get on it though.

i unplugged my o2 sensor and it didnt change anything. ive checked for vac leaks and found an intake runner gasket leaking, so i did the intake mani gasket. ive retracked the AFM as well.

what next? ive read possible FPR issue?

TIA!

[John_AZ]

Related? Usually "kissing cousins".

The O2 sensor is not used during warmup---ignored by the DME.

The sensor involved is the DME engine temp sensor towards the front of the block on top.

Now to the vibration. Is it constant even after warm up between 8-900 and 1100rpm?
If it stays constant it is usually a sign of bad motor mounts MMs.

You can see the OEM idle spec ---it is pasted to the inside wheel well passenger side. +- 900 rpm?

My idle does not increase during cold warm up---it stays at ~950.

Your early '84 944 has the early auxillary air regulator works like the late ICV idle control valve. Some get sticky--oil slime and do not work well. You could try to clean it???? If you look inside-it has a big disc that moves.

Pelican Parts - Automotive Parts and Accessories - Porsche & BMW

Now the boring stuff.
Clean all grounds. Clean the battery cable ends--No corrosion.
Porsche says to clean all electrical contacts on top of the engine.

GL
J_AZ

[Gawernator]

Idle not changing is pretty normal, mine stays the same whether warm or cold. ~900-950

[PDX-944]

Originally Posted by John_AZ

Related? Usually "kissing cousins".

The O2 sensor is not used during warmup---ignored by the DME.

The sensor involved is the DME engine temp sensor towards the front of the block on top.

Now to the vibration. Is it constant even after warm up between 8-900 and 1100rpm?
If it stays constant it is usually a sign of bad motor mounts MMs.

You can see the OEM idle spec ---it is pasted to the inside wheel well passenger side. +- 900 rpm?

My idle does not increase during cold warm up---it stays at ~950.

Your early '84 944 has the early auxillary air regulator works like the late ICV idle control valve. Some get sticky--oil slime and do not work well. You could try to clean it???? If you look inside-it has a big disc that moves.

Pelican Parts - Automotive Parts and Accessories - Porsche & BMW

Now the boring stuff.
Clean all grounds. Clean the battery cable ends--No corrosion.
Porsche says to clean all electrical contacts on top of the engine.

GL
J_AZ

it vibrates pretty bad when cold, but after warm up it stops vibrating. same RPMs as when cold though.

i was going to clean the ASV/AAR/hundred other names when i did the intake mani gaskets, but i was running out of time so i couldnt. hate to have to do them all again. cant i plug it and see if it makes a difference? i thought i read that somewhere... hmm.

[Gawernator]

Could be a bad DME temperature sensor. I got the Bosch one for like $20 and it helped my cold starts. Try unplugging the sensor and see if that helps. It should default to "cold operation".

[VirginiaF1]

Originally Posted by PDX-944

.. at cold start, it vibrates quite a bit at idle. idles about 8-900 (same cold or hot). is it supposed to idle higher when cold? why isnt it if so?

any time i push the clutch in, the idle dips a little then settles. its not that bad, but it shouldnt.

what next? ive read possible FPR issue?

Howdy..
Same symptoms last year when I took ownership, so far I have yet to replace the FPR and Damper which are from 1999. Original Motor mounts..

But so I have replaced the DME engine temp sensor, O2 sensor, sparks, Ignition Coil, Distributor & Wires, Fuel Filter, Air Filter and DME Relay.. Also, raised idle a few hundred to 1100...

Bingo! Now idles like an airplane.. Summer or Winter. Clutch In, Clutch Out.
Just Lovely.
Best Wishes..

[PDX-944]

do you know which of those resolved it?

i unplugged the temp sensor, the car doesnt start without it

[Gawernator]

...wtf? Mine started unplugged....

[Gawernator]

Originally Posted by PDX-944

do you know which of those resolved it?

i unplugged the temp sensor, the car doesnt start without it

It was probably a combination of all. Everything I replaced added up to a progressively smoother idle and better running engine.

[Ederd]

buy a multi meter and a notebook. consult clarks, haynes, and

http://www.eucc.dk/

. spend hours upon hours being confused and bewildered. eventually things will begin to make sense. trial and error my friend...trial and error.

[PDX-944]

Well I AM a mechanic. Lol
I spent a good 10 hours with a multimeter today chasing an electrical drain on an Audi a6. Not fun!

At any rate, I'm new to Porsche and am just looking for a starting point. Every issue has been had by someone at some point, but I'm not into the "throw parts at it and guess" deal. It's most probably a fuel issue or a vac issue I think.

Am I incorrect that to test the asv I can pinch off the line and it should do _____?

The fpr seems logical too for inconsistent acceleration, and perhaps an idle dip as well.
It appears I actually idle at 750 cold and 900 warm

[Gawernator]

That's a good sized change in idle speed... I'd guess some part would correlate to that symptom

[VirginiaF1]

Originally Posted by PDX-944

do you know which of those resolved

Yup... Each of them.
Consider that except for the sparx, everything replaced was 25 years old.
There is no Substitute.

[Gawernator]

I have replaced everything you replaced, minus the ignition coil and the DME relay. Why the relay? Also, I was under the impression coils either work or they just don't fire. That they don't "weaken" so to speak.