81 911SC - Interesting Expensive Learning Activity

[Navi]

Hi All

First let me start off by saying I am a newbie to the land of 911, and so far I am having a blast, I am starting to learn some stuff, but I don't really have a shop any more, and work keeps me overly busy... so the process is slow... but hear the story begins.

I found a nice 81 911SC, it had a cold start problem... 8 or 9 attempted starts until it started to run, after that it was good for the day... some quick internet searches indicated that it could be a "WUR" which is a the cold start pressure regulator?

Anyways I decided that since I really just wanted to drive the car, I would take it to a shop and pay the experts to make it sing.

The nice folks told me that I needed a new air box (yes it a pop off valve installed in the old one), I said OK.... much cash later I got the car back and "same thing"

The nice folks messed with it for a couple of weeks and installed a "WUR" bosche pressure regular ( they installed a MB unit, they said much less cash and almost same output)....much cash later I got the car back and yes it starts and goes OK

But.... on and off, and not all the time, and sometimes all the time, intermittantly the car will not idle without surging between stall and 2500rpm, this is when at a red light or stop sign... smooths out when I start to go... and sometimes if I just simply keep my foot on the pedal a bit it smooths out. Then, as fast as the problem started it just simply starts to work again

Now this is not the type of problem I want to had over to the nice folks at my local Porsche fix up place.... I don't mind spending the money, but I would like it to run good for a couple of days after the cash injection.

Any thoughts? Comments? Suggestions ?

I have already decided to start with:

- "new vacuum lines - all of them"
- "new spark wires"
- "paint detailing", hoping the car just needs some pampering?

Thanks

Navi


Thanks

[James Brown]

This is my take: MY 81 used to do that, then...removed all blowers, removed all A/C stuff, everything!, removed and backdated heat, REMOVED CIS, removed all vacuum lines (yes distributor included), removed CDI, removed cat, removed radio, removed everything I could find that was not needed/electrical. Installed front oil cooler, carbs, MSD, dissy. now the car starts, runs, stops, restarts hot, cold, easy to work on, cheap to fix (if it would ever break), lighter (2400# wet), drive it every day like I rented it! And it halls! about 247 rear wheel horse power! (jk)
I know, how can you at this point do what I did. Well, it is the journey not the fix. If you can't fix it yourself, bite the bullet and simplify your life. OR, keep taken it to shops for "experimental" repair for big, big bucks.
Oh, a paint job can never hurt!!! And it's a 911SC not a Carrera

[IROC]

Originally Posted by Navi

Any thoughts? Comments? Suggestions ?

You just need to find someone who is really well versed in CIS. A set of pressure gauges will tell you a lot as CIS is all about the pressures. If they're not right, then you're going to be chasing things forever.

[mike635]

I have an '81 SC and have worked on the CIS system, they're pretty straightforwward if you have some basic test equipment (CIS pressure gauge, can get at NAPA) voltmeter, and a few other simple items.

From what I know of the system, if I had my car at a shop for cold start problems and they replaced the air box, I'd be looking for a different shop.

You need to go through the CIS sytem methodically (get a Bentley manual) and verify the basics:

- Are the cold/warm control pressures and system pressure correct (specs are in the Bentley)
- Is the lambda system working properly (shouldn't really effect cold start but you never know)
- plus a few other simple things to check.

Not sure if you're up for this on your own but if so, there's a ton of threads here if you search.

Mike

[kiwiokie]

I would post to the forum a request for recommended repair shops in your area. From memory the SC airbox gained cold start enrichment somewhere around 80/81 so that may not have been a bad suggestion but the use of an M-B WUR sounds a little suspect.

[john walker's workshop]

if the lambda system is not functioning, the mixture leans way out. a shop that doesn't know it's dead, cranks the mixture back up to what they assume is normal. once in a while the relay that activates the lambda system kicks in and the system then goes way rich, hence the surging idle. just one scenario of course. remove the domelight fuse and see if the idle drops off and gets rough. it should if the system is working. the relay gets power from that fuse. the relay is under the right seat, in front near the tunnel. you can also unplug the relay for the same effect.

[Superman]

Often times, we Pelicanheads have a couple of options. We could spend weeks and months fiddling with adjustments, replacing expensive CIS parts and scratching our heads........or we can simply listen to John.

[Jdub]

I'm with you Super - you just can't match experience over the years.

[Navi]

Thanks for the tips, I'll check some stuff this weekend and post the results

Thanks

[T77911S]

james was headed in the right direction. it might be better to just remove the CIS and replace ALL rubber and gaskets. youve got intake runner rubber, injector O rings, injector sleeves just to mention some of the things that need to be replaced. take your time and take pictures. there are a lot of very smart people here that will guide you.

[boyt911sc]

Navi,

Where are you located? The car looks familiar to me (????) but I could be mistaken. Thanks.

Tony