The 911SC Defects

[vizail]

Trough the years I've noticed that the 911Sc between,1981 and 1983, get the boot from their owners more frequently. Besides the updates and modifications sugested by the 101 Porjects Book, the car is a great one..,but when it comes to the Fuel Injection System K-Jetronic w/ the Lambda valve and sensors, the Germans really went backwards. So many things can go wrong that the diagnostic's is very hard. The passing of the years trial and error mechanics, and the constant search for information, purchasing of tools (O2 Sensor electric meter) maintaining the wires that cary small voltage etc. etc. will take some time to get used to and will make you an expert.
Once you have it calibrated mixture and Air , correct ignition timing ... Is like music to your ears.

How about some imput from the 1981 to 1983 SC owners..!

Vic

[SpeedracerIndy]

In todays computer controlled car age I think most people expect an instant response as to the cause of their engines malfunction. With the CIS it's like you said, trial and error. That gets frustrating and expensive VERY quickly. I don't mind a the trial and error as long as the Porsche isn't my daily driver. I do mind the expense though, and that causes me to ignore some problems that creep up now and then that don't need immediate attention. Some of those CIS components are expensive! That being said, my car has been and is running pretty well (knock on wood!).

Also there are a few that I have seen who have deleted many of the unnecessary CIS components, such as the decel valve, to make the system more simple and reliable. As long as you don't have to worry about emmision inspections, that sounds like a good idea to me.

Edit: oh yea, I'd hardly call these traits of the SC (and earlier CIS cars) defects! The SC is still one of the best (if not the best) 911's you can get for the money.

[T-Bone911]

My 1981 was a garage queen when I purchased it. After new fuel filter, accumulator, wur, plugs and wires it has run great. Only fault in the last 5 years was the lamda computer, expensive but running great again. Not a high tech system but durable, so far.

[mb911]

I have an 81 engine in my 77 and it works great no problems still the oem lambda..

[Formerly Steve Wilkinson]

I put carburetors (PMOs) on mine. Runs great. Current overall fuel economy is 18 mpg.

Stephan

[Paulporsche]

I agree! For the past 13 yr/65ooomi I've had an 80 engine w/ CIS (no lambda). Prior to that, a 2.7 w/ CIS. Both have been virtually trouble free in the fuel injection department. The only exception was an out of spec WUR last year. Thanks to comments on this board and a few hammer taps to knock the plug, things are back in order. And this is without a fuel pressure gauge!

[IROC]

I've always felt that CIS was one of those things that when it's running good, it's a really good, reliable system and when it's not running good it can be a nightmare.

Luckily, the CIS on my old 2.7 was the former. Other that a pesky WUR, I never had any problems out of it....

Mike

[TerryH]

Knock on wood here too. I've had mine 54 weeks without a hiccup. Starts right up and idles smoothly every time. I've read a few nightmares, but none here to tell.

The down side, if you can call it that, is I'm not learning much about the fuel delivery workings because I've not had to work on the system. But that's probably a good thing, eh?

[sraiken]

I am in the nightmare mode with my '80 CIS. If I set ign. timimg to correct it idles way too high. I have spent hours looking for air leaks, put in new seals, new air bypass. I have richened the mixture which seemed to help which lead me to look for air leaks again. I currently retard the timing to get a reasonable idle level that still will give a good power band. Luckily I have other transportation. I love the car and working on it but I would like to get on to other things.

[JackT]

CIS requires a really good 911 machanic. My car was cutting out over 4000 RPMS. I had the dealership machanic look at it. He replace the injectors, plugs, plug wires, fuel additives, air filter and Oxygen sensor. Car still cut out over 4000. Dealer told me I needed to replace my fuel regulator, (very expensive) I took it to Les at Docs Garage in LExington S.C. He listened to it, drove it, adjusted it, then told me it needed a Warm up Regulator. He told me to order it from Vertex because they had it cheaper than what it would cost him, I didnt know about Pelican Parts at the time. I called Vertx and the fellow taking the order said that it didnt sound like a WUR problem and that my machanic was wrong and that once I used it, it was mine. I told him to send it anyway, Les changed out the WUR and no more CUt outs over 4000RPM's.

[Superman]

CIS systems work beautifully and need nothing. Usually. And when they need something, follow the troubleshooting steps. Failure to do that will cause you to imagine that CIS systems are troublesome, unreliable, mysterious, etc. That's false, of course. Unless you've tried to repair a CIS system without following the steps.

[mede8er]

Took awhile but I finally understand this system....Bluebird is steady and reliable.....

That being said I'm putting PMO's on her ASAP........

[sammyg2]

CIS equiped engine suffer from one thing:
the shotgun mechanic.
In other words, instead of doing it right they guess, replace or adjust something, then try something else or just replace everything they can think of and hope they got it right. Eventually they might get it assuming they don't screw everything else up along the way.

If instead, they get the proper tools these cars are fairly simple to diagnose and fix.

This board is chocked full of owners trying to solve a CIS problem and they have NEVER checked the fuel pressures.

The factory manuals are very straight forward: make sure the ignition is working properly. Make sure you don't have vacuum leaks. Check cold control pressure and system pressure. Check warm control pressure and system pressure. Etc.

CIS is not something you can guess at.

[clevy70911T]

I've driven many VW, Saab, BMW, Porsche with CIS and have always loved it. Most cars were very reliable beaters and always started well in cold temps. Through the early years, I learned how to use a multilmeter and diagnosing problems by going through proper tests rather than guess and replace. It's paid off now I have my SC. Once familar with the various tests on each component, it makes diagnosis alot easier. Not the best FI system, but reliable and simple IMHO.

[Paulporsche]

I think Sam has a good point. In my case I was so familiar w/ my own car after owning it for so long, that I was able to diagnose and solve my problem easily, quickly and cheaply, with the help of the friendly Search button. I had the benefit of observing the car running perfectly and then seeing it go south.

I have since taken up the advice of various board members and have purchased the fuel gauge. At the very least I can use it to confirm my recent fix, and who knows, it might come in handy in the future.

[Hladun]

I too agree with Sam. CIS systems are very reliable and easy to maintain once you understand them. My 78SC will start in -30F temperatures with no problem.

But there are many things that can be adjusted and they're usually adjusted wrong. The solution is then often adjusting something else even more wrong.

[SpeedracerIndy]

If you really understand how the system works it saves a lot of frustration. When I first got my car I didn't take the time to learn how it works and would just blindly post a question on here expecting a quick and easy answer for the fix. When I finally took the time to learn how and why all the components worked, I stopped asking so many dumb questions. It really is an ingeniously simple system.

[sraiken]

OK, I will stop asking questions. Bosch CIS books on order and gauge for control pressure testing.

[Rick Lee]

DrewT, I'm curious how a bad WUR affected your car over 4k rpms. I don't take my car above about 3700 until the oil is at 140 deg. By that time, I thought the WUR is totally out of the loop. Doesn't it only affect things in the first two min. of warm-up? I'm pretty sure my WUR is shot, as my car is pretty much undriveable for the first two min. after cold start-up.

[Paulporsche]

Rick,

Remember the WUR is actually a Control Pressure Regulator. It affects the mixture whenever the engine is running, not only during warmup. The AAR (aux air regulator) only has an effect (raising the idle speed) for a few minutes during warmup.

Drew's problem could have been that his mixture was too lean once warmed up and/or he didn't get the extra enrichment the WUR is supposed to provide @ WOT.