rbuswell

Car: '82SC (Built 09/1981 so it just had it's 25th birthday)
Problem: Stumbles and dies at idle when car is warm and only when ambient temperature is over 80 degrees. Haven't noticed much trouble when cooler weather outside.
Already done: Looked into gas tank and it is very clean. Replaced noisy fuel pump, fuel filter, O2 sensor and accumulator because it seemed like the best path to solving the issue of hot stalling given age of car and it was suggested on several other posts.
Other symptoms: Car starts and runs well when cold accept for slightly rough idle as noted below. Will restart right away after it dies. Can keep it running by pressing brake and accel. pedals when coming to a stop.
Sidebar: Car runs much more smoothly at speed with noticeable power improvement since repairs. Somewhat less smooth idle when cold.
Why all the egg: I suggested on another Rennlist post with a similar issue that my problems were solved and that he should think about taking the same path

How about: 1) Cleaning ICV. Seemed to help a couple others with similar problem. I've seen many posts that say it is an easy DIY but no procedure on how to actually remove and clean the ICV. Not mentioned in Bentley or Haynes. Is it called something else in those books? 2) WUR testing and (gulp!) replacement. High or low on the list for this issue? 3) Other suggestions that could be high on your checklist 4) Simply adjusting the CIS or having it done. Idle RPM right at 950 most of the time and I'm not displeased with the performance otherwise although I think the car burns too much gas. I don't push it real hard.

Comments and ideas really appreciated.

Brett San Diego

If it were me, I would start with checking the fuel pressures: primary pressure, cold control pressure, and warm control pressure.

Brett

rbuswell

Anyone know the actual procedure for removing the ICV to clean? No suggestions so far.

Dan Cobb

I wish I had even the slightest help for this one, but I have never owned an SC, thus I have no experience with the injection or electronics.

I will give it a bump though.
+++

Peter Zimmermann

Pardon me for being dumb - what's an ICV?

You problem is a tough one with the car on the hoist - over the Internet even more so. You don't mention having done the most basic setting of all, setting the CO%. What is it set at, and does the car still have its catalytic converter?

What elevation is your town?

Pete

911 Rod

I know you are just pulling our legs on this one Pete.
ICV (Idle control valve) did not come out until the 3.2, so you shouldn't have one.
You will find it in the Carrera Bentley.

Peter Zimmermann

Hi Rod! Yep, you got me this time. I kept going back to check if the SC somehow turned into a Carrera...
Pete

rbuswell

Got the newbie again. Ain't it fun?

Maybe Rennlist should separate the amatuers like me who bought the car to work on and enjoy from the professionals who know it all (kind of like separating general aviation airports from the where the airliners land) so we don't waste your time or get in your way. It would be safer for everyone.

I used a search, I read a post, it talked about the gummed up ICV and it provided some relief to the problem for another user. As I said, it didn't show up in the Bentley or Haynes so I thought it could be called something different. I saw no mention of it as not a part of CIS systems.

Thanks for the help and encouragement guys.

Peter Zimmermann

rbuswell: Don't you dare leave! OK, now let's get back to your problem. My earlier post asked what your CO% is set at, if your car still has a catalytic converter, and what elevation you live at (all three of these can provide info toward finding a cure for your problem).
Pete

rbuswell

I don't have the test results readily at hand but the car passed the Colorado dyno test fairly handily in March for CO but pretty close to not passing on hydrocarbons. The Colorado test is pretty stringent (not as tough as California, I would guess). It does still have what appears to be the original cat and we live at about 6,200 feet but it has acted up as low as about 5,000 feet above SL. My car is still required to comply with emissions laws due to age but can be exempted if I register it next time as a classic car. I have considered getting a cat bypass for performance reasons.

I don't own any other test equipment to determine pressures or CO yet but if needed I would sure consider getting it.

Brett San Diego

rbuswell: If you want to be able to do DIY work on your CIS system you should get the proper tools. First and foremost is a fuel pressure test gauge, around $100 from various sellers (go on Froogle). Actually, probably the most important tool is a book or two on the Bosch CIS K-jetronic system. Find them on pelicanparts.com, but try amazon to buy them (usually cheaper). There is a lot to learn. You can also get a CO analyzer (or air/fuel meter), but they can get expensive. To me, the cheap one (Gunson brand) is suspect on accuracy. I've decided that I'll let a professional shop do my CO measurements and fuel mixture adjustments. It was only $90, and you don't have to do it often, but it can make a world of difference.

If your car is new to you and you don't know when the mixture was last set properly, my advice is to take it to the professionals for a timing and mixture adjustment. Invest a little now. See the recent post from "der mond."

If you're not inclined to take it to a professional, you need to specifically answer everyone's questions in order to get proper assistance.

For the CO measurement that Pete is asking for, the exhaust gasses have to be sampled before the catalytic converter. There is a plug in the exhaust just before the cat that must be removed so that the sampling probe can be inserted. In order to properly adjust the mixture, you have to know exactly what the engine is exhausting. The catalytic converter carries on a combustion process after the engine, and so it modifies the ratios of exhaust gasses. Routine tailpipe emissions tests sample the exhaust gasses after the cat, so these test numbers are irrelevant for tuning the fuel system.

good luck,
Brett

rbuswell

I retreived the Colorado emissions test. It read 33.6822 GPM with 45.0 as passing for CO but 3.6256 GPM with 4.0 passing on HC. I understand that this is post-cat and may not be of much help to Pete.

Here's my dilemma:

I've been trying to follow a logical path to fix this problem based on research in Rennlist and Pelican. I don't feel that the time and money I spent on the pump, O2 sensor, filter and accumulator was a waste of $ since a car that old likely needed those done anyway and the car seems to run much better. I bought a CIS troubleshooting book for $40 that didn't seem to offer much assistance for my problem (may have been the wrong book) and the Bentley, and even the Haynes seem to have some pretty good info.

The car seems to run really well except for this hot weather stalling problem and fuel consumption. I'm not opposed to finding a Porsche wrench to do the CIS adjustments (although I want to do as much on my own as I can since working on the car was as much my reason for buying it as driving it). My dilemma is that I'm not comfortable that it will help. This set of symptoms and the way the car runs, generally, leads me to think it is some obscure problem, not basic, general adjustment. If the car is way out of whack, it should run poorly most of the time. But I don't know the cars like you guys so that's why I'm asking.

If anyone has a recommendation for a Porsche shop who knows CIS well in Denver, let me know. The Porsche-only shops I've spoken with have underwhelmed me with specialized knowledge and overwhelmed me with projected costs ... and no, I'm not naming names.

Brett San Diego

Really sounds like it could be related to the mixture setting, which is why Pete wanted your % CO numbers. If you have never had the mixture set properly, this is a must do before anything else, IMHO. You can replace all the parts in the world and none of them will bring your mixture into line.

Since it runs fine otherwise, I would just take it to a shop and ask them to do a timing and mixture check and adjustment, nothing else. Call for a quote on just that, rather than an open ended "what will it cost to fix my car." My car ran "fine," too, but both the mixture and timing were off a bit, and it was so much better afterward. Again, it was only $90 (probably a 1 hr labor charge).

Brett

Peter Zimmermann

rbuswell: Yep, Brett has the whole thing right on the money. Now your problem, on the other hand, is that I suspect it's running rich. This might have been done intentionally to mask another problem (CIS system pressure, cold control pressure, OXS/frequency valve malfunction, altitude compensation problem, etc.) and if that's the case the CO reading is the first place to go. As Brett stated, the CO reading out the pipe, on a car with a cat, is useless - the tune setting must be made pre-cat, and then you can go from there. If the TV doesn't work you check if it's plugged in, if CIS doesn't work you check the CO as a starting point.
Pete