cold CIS problem

Bill wjw · 11-30-2009, 09:11 AM

I am experiencing lurching, popping and hesitation on my 1982 SC only when cold. Once the engine has warmed up it drives reasonably well, but maybe just a little bit off perfect. It is hard to tell there are no signs of missing or power loss. It has so much more power that the 912 I am use to driving. I am new at trouble shooting the CIS . I have owned the car almost two years now and it is in great shape. I have been reading everything I can find on the CIS and beginning to understand much of how it works. I am still vague on the oxygen successor functions. I am working slowly and methodically on the car to regain the performance it had a month ago when I drove it across country.
Pressure check test:
System pressure – 4.6 bars 67 psi
Cold control pressure – 0.9 bars 12 psi at 45 Degrees C
Warm control pressure – 3.4 bars
New cap, rotor, plugs and fuel filter.
Additional questions – 1,3,4 and 6 injector sleeves are lose and can be moved in and out 1/8 inch by hand. Checking them with carb cleaner shows no change in engine speed. I have searched for vacuum leaks and can find none. Is it advisable or possible to remove and replace injector sleeves with the CIS still on the engine and in the car? The PO had replaced the injectors and injector O rings. How many miles between valve adjustments? I have a 912 and adjust every 3000 miles. I am game to try this on the 911.
I can pull the WUR bring it to the machine shop at work and make it adjustable to pull up on the plug to increase cold pressure. Should this be my next step or should in investigate other areas first?

ossiblue · 11-30-2009, 09:36 AM

Quote:

Originally Posted by Bill wjw

I am experiencing lurching, popping and hesitation on my 1982 SC only when cold. Once the engine has warmed up it drives reasonably well, but maybe just a little bit off perfect. It is hard to tell there are no signs of missing or power loss. It has so much more power that the 912 I am use to driving. I am new at trouble shooting the CIS . I have owned the car almost two years now and it is in great shape. I have been reading everything I can find on the CIS and beginning to understand much of how it works. I am still vague on the oxygen successor functions. I am working slowly and methodically on the car to regain the performance it had a month ago when I drove it across country.
Pressure check test:
System pressure – 4.6 bars 67 psi
Cold control pressure – 0.9 bars 12 psi at 45 Degrees C
Warm control pressure – 3.4 bars
New cap, rotor, plugs and fuel filter.
Additional questions – 1,3,4 and 6 injector sleeves are lose and can be moved in and out 1/8 inch by hand. Checking them with carb cleaner shows no change in engine speed. I have searched for vacuum leaks and can find none. Is it advisable or possible to remove and replace injector sleeves with the CIS still on the engine and in the car? The PO had replaced the injectors and injector O rings. How many miles between valve adjustments? I have a 912 and adjust every 3000 miles. I am game to try this on the 911.
I can pull the WUR bring it to the machine shop at work and make it adjustable to pull up on the plug to increase cold pressure. Should this be my next step or should in investigate other areas first?

Without knowing the wur#, the pressures you posted look good, though I think you typo'd the ambient temp. The symptoms you mention could be due to too high cold pressure but yours appear to be in spec so there's no need to adjust the wur to higher cold pressure.

If you're sure your ignition is in order, then you might get the valves adjusted before you dive into CIS diagnosis--take care of one thing at a time. Since the fuel pressures check out (someone can confirm when your wur# is posted), your next check is to see if the Auxilary Air Regulator is functioning properly, or other obvious sources of air leaks as it does sound like you have a lean running condition.

I have no knowledge on the oxy. sensor, though someone will certainly respond who does.

psalt · 11-30-2009, 09:38 AM

Hello Bill,

Is there an error with the cold control pressure, 45C is the warm spec, do you mean 10C ? There is more to cold running performance on an 82SC than basic CIS fuel pressure, you need to figure out what the lambda system is doing. There are two cold acceleration functions on your model. Even if the pressures are spot on, the engine will not run properly if the lambda system is not working. There is a test port under the plastic cover in the engine compartment and if you have an analog dwell meter the system will tell you if it is operating correctly. If you don't have a dwell meter (borrow one) at least make sure the fuse #18, interior light , clock, trunk, is OK and the relay under the passenger seat clicks when you start the car. Maintanence is much less than a 912, 15,000 miles for a valve adjustment. It is helpful to read the Bosch manual on CIS lambda, the Bentley manual is OK, but there are a few errors. Unfortunately, there is no completely accurate description of the 82 911SC CIS lambda system in print, and very few people actually understand how it works. You can view all the functions of the FV through the test port with a dwell meter and this is the best way to understand what the system is doing. Good luck.

T77911S · 11-30-2009, 09:52 AM

its nice to see someone start off with all the basic questions already answered.

listen to paul.

popping and such would equal lean.

sounds like you are on the right track. try to get those injector sleeves replaced. check all the bolts bolting the CIS to the heads. the intake gaskets can leak too.
the rubber boots on the runners are another leaky spot.
i know these are things that should effect cold and hot, but paul has covered everything else.
timing- advance and retard
other air leaks. remove oil cap and for check drop in RPM.

Bill wjw · 11-30-2009, 09:59 AM

I am sorry guys it was 45 degrees F in my unheated garage in Northern California

Hesse James · 11-30-2009, 10:42 AM

Hello,

I have the same problem with cold start. After checking the WUR I saw that it has no current at all. When I measured the 14pin connector there was power on the pin but when I reconnected the 14pin power to the WUR was lost. So I tried to power the WUR and to my surprise the car started up immediately. I am now checking what is wrong with wiring on my 74 CIS.

1990C4S · 11-30-2009, 10:44 AM

Sounds lean. Verify you don't have a vacuum leak and lower the cold pressure if necessary.

The advice above is correct.

Paulporsche · 11-30-2009, 12:41 PM

Your cold cp should be about 1.2 to 1.6 bar @ 45F, according to the graph, so your .9 seems OK to me. I actually like to see the cold cp a little low like this to aid starting. (Others may disagree)

Since this is the case, the previous suggestions re vac leaks and the lambda system seem to be what you should be checking next.

Bill wjw · 12-01-2009, 09:28 AM

Thanks to Paul I found the problem and the SC is running great. I checked the oxygen sensor control unit power relay under the passenger seat. I turned the engine over 3 times while holding the unit in my hand and could hear nor feel nothing. I unplugged it to check for corrosion on the connections but they were clean. When I plugged it back in and turned the engine over I felt it click. I tried it a couple of more times and it continued to function. I started the car and took it for a drive. Ran just the way it should. I ordered a new ten dollar + change relay and some other maintenance items. Thanks so much for your advice Paul. It saved me time, frustration and most likely a lot of money. Not to mention the driving time that I was missing. Thanks to everyone that offered their advise.

psalt · 12-01-2009, 11:38 AM

Hello Bill,

I'm glad you found the problem. If you like working on the 912, the SC will tell you a lot more once you learn to read the FV duty cycle with a dwell meter. It's not quite OBDII, but it will tell you that everything is working and can be used to set the mixture without a CO meter.