1982 SC spark plugs cat bypass new cdi
 

So I have a question. 82 sc stock 3.0 liter. 70k on the car and I just changed over to the classic retrofit cdi box and the cat bypass pipe. New wires rotor cap etc.

I have owned the car 6 years and I never did the plugs. This is a wr5dc plug. God knows how old it is… car is driven around town and spirited drives but not a lot.

Yesterday took it for its first drive basically around town to make sure there where no issues with it and all was good. I let it run when I got back and just noticed an erratic idle which it never had before.

Granted it was 55 degrees outside but the car was somewhat warmed up.

I was going to do the plugs anyways and I have read when you do the cat bypass some cars have an erratic idle which you would need to Richen The mixture for which I don’t want to do… I’ll buy a new catalytic converter and sell the bypass pipe.

So which plug should I use with the new bypass pipe and cdi box?

The plug is a greyish tan the picture makes it look more white.

Thank you everyone

Forget the cat bypass and everything else unless you sorted out the issues! When you trying to cure such things by adding other parts you confuse yourself and any other mechanic working on the car! And sorting out issues on a CIS 911 is expensive - anytime! More and lore less people are able to repair these cars, most of them claiming they're experts but they do the same as many others - hiding issues by tinkering around instead of sorting them out.

You write about the erratic idle. The by far most often issue related with that symptom on these CIS systems are vacuum leaks!After that fuel pressure issues are the next. But at first - chase for vacuum leaks.
If there are some minor leaks, they sum up to bigger issues over time. Go and get one these electric smoke generators and put the whole system under smoke and solve the vacuum related issues. only if proven that there are absolutely no vacuum leaks continue to fuel pressures, mixture, ignition timing etc. But only then!

Thomas

The thing is I had no issues prior to doing this, car ran perfect!

This is even a more proving fact that most likely a vacuum leak has happened. Rubber is stressed on an aircooled engine like on a 911. Additionally the CIS is quite sensible on vacuum leaks! Again: Stop guessing around - make the vacuum checks at first!
I own this smoke generator:
https://shop.autooltech.com/product/smoke-test-machine/

This gives you everything you need for a proper inspection of CIS vehicles. In my opinion, this is one of the tools that a 911 CIS owner absolutely needs. It can save you a lot of stress and money. It's the cheapest and most sensful way to narrow down the issue. Only if proved that there are vacuum leaks go to further steps like I said.

Thomas

Ok and where am I connecting this too?

https://forums.pelicanparts.com/porsche-911-technical-forum/1174607-need-cis-help-course-2.html#post12421036

Are some of us just spitting out the same answers for every question?

Is there a need to richen up after cat delete? Don't know.

Does your car idle well with proper fuel ratio and cat delete? Yes.

What plug with new cdi? Don't know, good question, hopefully the same as recommended by Porsche.

Does changing your cat affect your vacuum leak? That wasn't a question and no. Is it possible that a vacuum leak developed, yes of course, should you start your study there?

Would it make more sense to ask if your bypass has an imperfect seal and changing your lambda reading if the frequency and o2 lines are hooked up? Yes.

Could he have screwed up the o2 sensor feed while manipulating the cat to bypass, yes likely. What I'm getting at is there are more reasonable question to ask before dumping the same old answers. Each case is specific.

Phil

The o2 sensor I replaced last year and I was pretty careful swapping it over.. I think I’m going to smoke the motor anyways as I have never done that… guess I’ll start there

In that case, check out Klassik Automotive Training School

https://www.youtube.com/watch?v=RWuxaR6upIQ

This vid came out 4 hours ago and he shows specifically how to test air leakage with a smoke machine. Might be what you're looking for.

My '82 has 260,000 miles on it. Engine has never been opened to my knowledge, and I've had it 22 years and put the last 110,000 miles on it. I've run the OEM cat until it wouldn't smog, ran a cat bypass for a year or two, and for the past five years ran the single stage 49 state cat from our host, which seems to clean up the exhaust just fine and passes the sniffer test in California. Thru all this, the idle has never needed anything other than a few minor adjustments following tune-up or fuel mixture adjustments.