giddyupp

Symptoms - When cold, car starts right up every time, though it does turn over once or twice more than I might expect. Idle (in Park) goes straight to around 1200, drops down to around 700 and then immediately goes back up to around 1100 and pretty much stays there. Drops to around 850 when in Drive. Idle is rock solid and does not waver at all after the initial start up.

Items checked and completed so far
Just completed top end refresh, including new TPS, all new rubber and vacuum lines, (Witchhunter) cleaned and checked injectors - Symptom did not change -same before and after
Checked and double checked for vacuum leaks - found nothing
TPS definitely has audible click on and off
ISV was not replaced as it looked like it was pretty new. It was way cleaner than anything else in there.

Thoughts -
MAF - the car seems to run really well - though if I really punch the accelerator there is second or two of hesitation before it kicks down (not sure if this is transmission or engine issue). Can the MAF course high idle. It does look like it has been taken apart before but it was pretty dirty (like everything else in there) and did not look like something recent.

Fuel Pump - Could a weak fuel pump be causing the additional turn on start up and have anything to do with the high idle.

Idle Stop Screw - What are the chances it could be the screw. It does have the yellow paint but it is not all there. On first look I felt it had not been touched but as I am running out of ideas Im looking for any possibility. I have attached a photo.

Computer
Looks like it was rebuilt in 2012 - it has a rebuild date sticker on the side. Im assuming this is ok

I have spent hours here searching and it seems that most threads point to vacuum leaks - but as I have said I have checked and re checked. I know safulop has a similar thread and wasn't sure if I should start a new one or jump onto his. Can someone let me know if I should re post onto that thread.

Question
Am I missing/forgetting something and where do I go from here ?

Was really hoping to get to Sharktoberfest this weekend but don't really want to drive the car all that way with this issue.

Thanks as always in advance for any advice and info.

John Speake

Have you set up idle CO and speed as per the WSM ?

See Vol. 1 A pages 24-204 to 207

giddyupp

My car is the 32V - does this still apply? It was my understanding that there was not idle adjustment in the WSM for this.

John Speake

Yes, those pages refer specifically to the 85/86 US 32v cars.

Speedtoys

Its fine..bring it to Sfest,a nd we'll all brain on it there.

zekgb

Yes, there will be lots of S3's there to swap known good parts into yours to get it diagnosed. As per my other thread I also want to go through the idle CO adjustment process and we can do it down there as a tech session.

Mrmerlin

the ISV is a wear item.

for your car to run perfectly all of the pieces should be replaced this includes,
CPS ,TPS, ICV , O2, Temp 2, MAF and readjusted, new ignition wires and caps and rotors, fuel lines, spark plugs, the short TPS harness and the temp 2 connector, any rubber parts that touch the intake

giddyupp

So I checked the WSM and it seems to me that if the MAF is working correctly there should be no need to make any adjustment to the CO setting. Is my assumption correct? Unfortunately I also do not have a CO testing tool.

Mrmerlin

NO, with a fresh MAF its starting point is set at 380 ohms,
with it installed you fine the mixture,
an old O2 sensor will change the readings always use factory parts

giddyupp

Stan - can you tell me which of the above would be the most likely culprit for the fast idle. The Temp 2 tested just fine and I do have a new TPS. I did replace all the rubber including several of the Bosch electrical connectors.

Im leaning toward taking the plunge and driving down to SFest. Would love you guys to take a look. Seems like high idle is a somewhat common problem and doing a tech session on hunting it down might be useful to more than a few.

Mrmerlin

I would take it to SF and let them have a look

byrdman454

Did you guys figure this out at SFest?

giddyupp

didn't make it - that whole work life balance thing didn't really work out -

and of course because I was working I didn't have a chance to look into it any further. Though after more reading and research I am definitely leaning toward a bad MAF. The hesitation at kick down is the main pointer - I think !

giddyupp

I pulled the MAF last night and am going to send it out for a checkup.

Also did some more re checking of connections and hoses. I pulled all the vacuum lines of the fuel dampers/regulators to see if they held vacuum. They all do, but this piece, see the attached photo (not sure what it is) does not hold vacuum. Can anyone explain what exactly this does and would this have any effect on idle speed.

zekgb

That's one of the two valves for the charcoal cannister, according to Greg Brown he doesn't think this one is necessary for the purge function to work correctly which is good thing since it's currently priced at $770 from Porsche. Cap the vacuum line and retest. On my engine the rearward plastic valve was blown and replacing it (thank god just $37)raised the measured vacuum from 15 to 17hg at the EZF.