CIS stumper of the day! (long)

thrown_hammer · 06-27-2002, 03:05 AM

Members of the board...
(I've always wanted to say that)
My CIS car has a problem that I don't understand. It was dying at stoplights so I took it to my mechanic yesterday. He hooked it to the machine and adjusted the fuel air mixture. Every time he revved it up the mixture would change when it setteled back down to idle. He thinks the pin inside the fuel distributer might be sticking and prescribes some techron fuel system cleaner and a long drive.
So I dump it in and go driving. Car no longer dies at stoplights but... I noticed that it pulls strong up to about 5,000RPM at which point it starts cutting out and stops accellerating. If I shift into the next gear it pulls strong until the same point and starts sputtering again???
In first gear it will go to redline, 2nd and 3rd it sputters at around 5,000RPM. Couldn't get it wound out in 4th or 5th due to traffic.
If I sit in the drive way in nuetral I can wind it up clear to redline with no cutting out or sputtering? I took it up to 5,000then 5,500 then 6,000 then redline.
Why would the car not cutout in nuetral or first gear but do so in 2nd and 3rd?
Any ideas???

Targa77 · Targa77's Garage

Sounds like an ignition problem to me. Check all sparkplug wires, points, cap, rotor. If you are using a Permatune CDS unit, go to http://www.permatune.com/Technical%20Support/Porsche/911.htm for troubleshooting ideas and checks.

thrown_hammer · 06-27-2002, 05:26 AM

Some more info. So far I've replaced the plugwires with steel braided units, new plugs, cap, rotor, fuel injectors, fuel pump, fuel filter. The car has stock ignition.

Targa77 · Targa77's Garage

Whenever an engine is placed under load, a weak ignition will usually rear it's ugly head. One note: I just read an article where an owner had a symptom where his car ran fine up to a certain point and would then start sputtering. It ended up being the fuel distributor. This, of course, was after the ignition had been totally checked out. If you are convinced that your ignition is okay, then I would check fuel pressure with the car under load.

Sunroof · 06-27-2002, 05:54 AM

Re-adjust the points...............

This happened to me too as well. By the way, the techron is stupendous stuff.

Regards
Bob
73.5T "home of the first CIS"

thrown_hammer · 06-27-2002, 06:03 AM

Do you have a spec handy for the adjustment of the points?

dougcl · 06-27-2002, 07:45 AM

Hey Thrown,
Install a new fuel filter first.

-Doug Clauder

JeffW · 06-27-2002, 07:59 AM

When does your car hesitate? if you floor it does it bog down or does it just do it when it gets to that certain rpm? Mine was doing the bogging down when it was floored and ended up bing the warmup regulator. Made the car run lean so if you gave it throttle, it got lots of air and little fuel.

thrown_hammer · 08:13 AM

It's at or about 5,000RPM in 2nd and 3rd gear. 1st revs all the way to redline. If I floor it it pulls strong up to 5,000 RPM in 2nd or 3rd. 4th and 5th were out of the question on public roads.

The car was at operating temp. 210F.

Targa77 · Targa77's Garage

point gap should be .012 or .014. Most books state that .012 is the correct spec but my Owner's Manual says that it should be .014.

gblumenstock · 06-27-2002, 10:13 AM

I vote for a vacuum leak. I recently had one that presented the syptoms of a dirty fuel filter.

Good Luck

GB

thrown_hammer · 06-28-2002, 03:00 AM

Here's an update. I went out and checked the condition of the cap and rotor. They looked bad. The P.O. said they were new when I bought the car... Oh well. Stopped at NAPA and bought cap, rotor and points. Put in the cap and rotor in the parking lot and went for a drive. Much better. I think when I change the points out it will fix the problem.
Once again I bow to the members of the board.

P.S. The rotor for my car was $35. They have an optional rotor for $6 that removes the rev limiter. For anyone interested in that kind of thing.

Todd Simpson · 06-28-2002, 08:24 AM

Shawn-
I hope the ignition tune up did it, if not, it sounds like fuel delivery to me. Your symptoms are EXACTLY what my MFI did a few weeks ago when it wasn't getting enough fuel. Great idle, and around town driving, 1st and 2nd OK, 3rd and 4th pretty bad, throw in a hill and I might has well have been in a beetle. You've got enough fuel to rev the engine up, but when it NEEDS fuel it's starving.

The warm up regulator should really be called the fuel pressure regulator, and it's a key part in the CIS system. The fuel pressure controls the mixture, so if it's off you will get too much air or too much fuel. Vacuum leak could create the same problem as it sounds like you are getting lean at high rpm.

Keep up posted on how you make out. My SC had a similar problem a few years ago, new WUR did the trick.

Todd

thrown_hammer · 07-08-2002, 03:02 AM

Here's an update.
I changed the points and set them at .012" gap on the high lobe of the distributer cam. Also as previously mentioned new cap and rotor. It seems to have fixed the problem. The car pulls strong from 3,500 to 5,000 RPM. After that the momentum seems to drop off a litttle but still goes to redline in 1st thru 3rd. Once again lack of road would not permit a 4th or 5th trial.

So my problem seems as if it were a spark problem and not fuel as I first suspected.