Cold out in upstate N.Y, idle way off?

robert walsh · 10-19-2008, 03:46 PM

Bought the car, '83 sc stock, in early spring and never had an idle problem, dead on 900 rpm's. Started the car today, mid 30's outside, and idle was at around 2000 rpms, after it warmed up it came dowm to about 1200 but was searching (surgind up/down) to find it's resting spot at 900 but never did. Car has no cat, bursch stright to exhaust with the 02 sensor. Never a problem till today on it's way to storage for the winter, now it's back home till I find the problem. Would outside temp effect the cis settings? All suggestions welcomed. I don't think it want's to be put away for the winter.

robert walsh · 10-20-2008, 05:38 AM

A fellow PCA member noted that my gas tank was down to about 1/8, he thought I may have sucked up some crap from the tank, said to dump some seafoam or similar fuel injector cleaner in with new gas and see if that clears it up.

chrisg252 · 10-20-2008, 07:26 AM

If you really have sucked some of the silt from the bottom of your tank up, you might be better advised to check the fuel filter. have you changes it recently? Fuel injector cleaners dissolve/remove built up varnish from the injector nozzles. A vacuum leak often results in symptoms such as you describe. Check your hoses for leaks and check that the clamps are tight.
Chris

robert walsh · 10-20-2008, 02:24 PM

I apologize, seems way too mant posts on this topic, if I could delte it I would. A quick question though, could a bad WUR be causing such a high idle, it seems everybody has problem with low or no idle.

VFR750 · 10-20-2008, 03:48 PM

Not sure about the WUR.

I did notice my Aux Air Valve is very slow to close when really cold. I tried a replacement AAV, but found the old one closed just fine with 12V. I have hypothesized that really cold air overwhelms the little resistive heater. Only when the block heats the housing, does it really get hot enough to close. Plus any leakage around the little valve enters the inside of the housing and cools the heater.

Long story short: I just ignore it. The high idle will not cause any harm.

If it runs fine when it's warm out, and only acts up when it's cold, then it's cold out.....

robert walsh · 10-20-2008, 04:09 PM

Mike, thanks for the advice, I agree with it, the high idle never came back to normal yesterday, flucuated between 1000 to 1200, seemingly hunting but not finding where it wanted to be, it just sucks putting it away with this on my mind, but your right, I never drive it when it's cold out, hopefully she'll wake up in the spring and be back to normal, thanks

Red Devil · 10-20-2008, 06:38 PM

I believe this is typical what you are experiencing. The temps you are talking about, expecially that cold, is going to definately affect your RPM's. It happens with my 80 everytime it gets cold. Mine loves the warm temps.

porsche930dude · porsche930dude's Garage

The same exact thing happend to me this morning. Coincidently also in upstate ny. On my way to work a 15 minute drive it still wouldnt idle down. On the way home in the afternoon it was fine

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by Red Devil

I believe this is typical what you are experiencing. The temps you are talking about, expecially that cold, is going to definately affect your RPM's. It happens with my 80 everytime it gets cold. Mine loves the warm temps.

Fellow SC owners,

The best time to know that your CIS car is in good condition is when the weather gets too cold!!!! Have we noticed lately that there were so many posts about starting problems the last 2 months? The cold weather really brings out all the hidden flaws of our SC's specially during cold start.

One of my yardstick for a well conditioned SC, is a one-start at dead winter even with frost on the windshield or maybe two attempts of the starter if you have not driven the car for a long time. Maintaining your CIS car to run good from summer thru winter is very simple, know and understand what are the specs you need. Fix or repair defective CIS components as needed and you'll have a very reliable and dependable car. Troubleshooting CIS problem is not that difficult at all.

Tony

robert walsh · 10-21-2008, 03:03 AM

Tony, this only happened sunday when it was coldest of the year so far, started perfect , had a high idle around 2000, thought it would drop when I hit the accelerator but it didn't. Lowered somewhat as engine warmwed but continued hunting never finding it's sweet spot. I agree something is not right, that "some" of these cars don't run correctly in the cold. I know mine was a florida car and was problably set up accordingly, simply meaning I think they were not concerned with anything to do with "cold" temps, from cabin heat to cold starting. I just noticed the big vaccuum control on the right side of the engine has the line to it plugged rather than inserted, I have no idea what that might be. or why they would do it.

Paulporsche · 10-21-2008, 05:33 AM

[QUOTE=boyt911sc;4250823]Fellow SC owners,

Troubleshooting CIS problem is not that difficult at all.

Sometimes it just takes a lot of time! LOL. Don't I know, Tony.

Robert,

Your FL comment may be on the money. That vacuum unit you mention is going to be either the AAR or AAV. The AAR raises the idle @ cold start and warmup and then gradually lowers it as the engine warms up. The AAV gives the engine more air to raise the sensor plate to aid starting. If you search Pelican mystery train, he has a great writeup on AAR repair.

robert walsh · 10-21-2008, 06:30 AM

Paul, in response to your comment, perhaps I should unplug the line and insert it back into the vacuum control and see what happens. I know it had an engine out service 4k ago in Florida, including tensioners, tune up, cat bypass w/o2, fuel accumulator and valve adjustments as well as compression and leak down tests, it is my feeling that at this major service it was set up, for some reason, to run without this AAR valve. Perhaps in the warmer climates they don't require the AAR? I don't know that any setting would deviate as to wether or not the AAR valve is being used or hose plugged. Not sure if it's the AAR or AAV, i believe it to be the AAR valve, about 4" round vacuum valve ,right side froward on engine.

robert walsh · 10-21-2008, 06:58 AM

Upon further inspection, the plugged line goes to the decelleration valve I believe. That appears to be the only diaphram type control the has 2 big hoses going into it and 1 vacuum line on the opposite side, that is the plugged line, don't know if that add's into the equation or not.

boyt911sc · boyt911sc's Garage

Quote:

Originally Posted by robert walsh

Paul, in response to your comment, perhaps I should unplug the line and insert it back into the vacuum control and see what happens. I know it had an engine out service 4k ago in Florida, including tensioners, tune up, cat bypass w/o2, fuel accumulator and valve adjustments as well as compression and leak down tests, it is my feeling that at this major service it was set up, for some reason, to run without this AAR valve. Perhaps in the warmer climates they don't require the AAR? I don't know that any setting would deviate as to wether or not the AAR valve is being used or hose plugged. Not sure if it's the AAR or AAV, i believe it to be the AAR valve, about 4" round vacuum valve ,right side froward on engine.

Robert,

The 4" round vacuum valve you're referring is not the auxiliary air regulator (AAR). If you have a Bentley manual, browse it and get familiar with CIS components in your car. Or look at the ad section for AAR for sale with picture. Getting to know the name and understand how they work in conjunction with CIS takes some effort and time. Most of us here started from knowing very little about our car and become informed over a long period of time. The sharing of experience and knowledge by the members of this forum is amazing.

Tony

Paulporsche · 07:28 AM

Why not try that and see.

Other causes of high idle can be a leaky Decel Valve, which you can try plugging the line to and see, a sticking sensor plate in the Mixture Control Unit, and an out of spec mixture (usually too lean).

A hunting idle is funny. Usually it means a too rich mix, although sometimes it can mean too lean.

The thick disk like thing on the passenger side is the AAV. The AAR is below and towards the back of the car. The DV looks like the AAV and is on the driver's side.

The Bentley Manual has info on this.

robert walsh · 10-21-2008, 10:15 AM

Paul, thanks for what I believe to be final clarification, it is the AAV which has vacuum line plugged off, it is , as you mentioned the diaphram disc shaped object on the right side of engine bay. I again apologize for my ignorance here, I have waddled (?) thru many mechanical issues this summer, no major ones yet. I frankly didn't realize how wide spread these issues are, relating to cold ambient temps and poor starting combined with idle problems. If I had, I would have done my home work prior to posting. Can you imagine, I thought the problem was unique to my car?? Sorry and thanks for the help.

kodioneill · kodioneill's Garage

Quote:

Originally Posted by robert walsh

Paul, thanks for what I believe to be final clarification, it is the AAV which has vacuum line plugged off, it is , as you mentioned the diaphram disc shaped object on the right side of engine bay. I again apologize for my ignorance here, I have waddled (?) thru many mechanical issues this summer, no major ones yet. I frankly didn't realize how wide spread these issues are, relating to cold ambient temps and poor starting combined with idle problems. If I had, I would have done my home work prior to posting. Can you imagine, I thought the problem was unique to my car?? Sorry and thanks for the help.

if you need a hand i have a small shop and work on 911's at my house in greenwich just down the road from you. if you want my # just reply with your email address and i contact you. 30years porsche, bmw master mechanic.

Paulporsche · 10-21-2008, 01:59 PM

Good luck and let us know what you are trying and what does or doesn't work.

As I'm sure you've noticed vacuum leaks contribute to a lot of problems w/ these things.

So do revised settings that are done to mask problems. You may find that something seemingly simple as a too high idle speed setting masking something incorrect in the mixture could result in an idle speed that stays high.

robert walsh · 10-21-2008, 02:14 PM

I'll take you up on the offer, email rfjwalsh@gmail.com

1982911SCTarga · 10-21-2008, 02:18 PM

Since you've got an '83, is your oxygen sensor plugged in and the lambda system (and oxygen sensor relay) working correctly? A sudden hunting idle possibly might be related to your lambda system running in open loop mode, where the frequency valve is unable to act to smooth out the idle when the car is warm.

Just a thought.

Brian