C.I.S. concerns

dd74 · 12-30-2002, 07:23 PM

On startup from cold, my engine runs fairly rough until it warms up. Would this be a fuel regulator problem? This is in a 3.0 with a hand choke (engine was transplanted into my '74).

Also..

After reading a piece on C.I.S. in a San Diego PCA article, it talks about the system's intolerance for dirt and moisture. I run 91 octane fuel and also plan to change the fuel filter. But is there anything else I can do (additives and such, possibly) that would clean out any dirt and/or moisture inside the system?

Thanks for all your help.

k9handler · 12-30-2002, 07:53 PM

techron works good, also a new fuel filter will help. Make sure the mixture is set correctly and check the warm up regulator.

dougcl · 12-30-2002, 08:40 PM

You can have the car motor vac'd. The system (made by Snap-On) replaces your fuel tank and fuel pump. You run the engine off of it and it sends detergent (ie Techron-esque stuff) through your fuel system. It also sends pressure pulses through your system. Cleans off the valves too, and should increase your idle vacuum by an inch or so.

Have you replaced your plugs lately?

Doug
1975 911S

MotoSook · 12-30-2002, 09:31 PM

If the car idles well when warm, you might suspect idle mixture is off. ALthough I don't disagree with the other guys. I have replaced the fuel accum, filter and even the screen in the tank since I installed the 3.0 in my 76S. All are low cost items and you can do it all yourself in an afternoon. In an old car like ours installing the lower cost parts is a great idea, unless it was done recently.

An Techron is cheap if it will prevent hours of troubleshooting.

Did the car start doing this recently? Any correlation to a turn in the weather (colder, I know you're in LA, but a 30 degree change might change the air density enough to affect you A/F ratio).

Check proper seating of the distributor cap while you're under the hood. Might not be related, but I always check when I have the back open. Same goes for plug wires and CDI connector..make sure they're all properly seated and tight.
Good Luck.

studog · 12-30-2002, 10:01 PM

The problem could be as simple as a small CO adjustment on your fuel dist. To rich. first check basic timming, points if equip , dist cap, wires and important VACCUM leaks, wiring to warm-up reg, therom switches etc
if it runs good when warm its not the fuel.
There is no choke on a CIS system, i think you mean the throttle lever on the e-brake.
hope this may help
Stu

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dd74 · 12-30-2002, 10:25 PM

Thanks guys for the information: I'll have to break out the old Haynes manual to EVEN SEE where half this stuff is that all of you mentioned. (I do know where the plugs are).

As for a choke: yes, the hand throttle is what I meant.

As for richness - yes, the engine does run rich. It was adjusted to run rich. At its current settings, however, I've found no adverse effects (other than the sputtering) by running it rich.

All this started happening around late Oct. I merely thought the engine was "cold" and needed to warm up a bit. To clarify things, the engine, when cold, usually starts on the first crank, then shudders and bucks for a few seconds before coming on real strong (dependent on where the hand throttle is positioned). After that, it idles fine. It sputters for a few blocks, then stops in total once its a bit warmer.

I don't know; is this natural cold 3.0 behavior?

I'm not having any warm start problems. Once warm, the 3.0 kicks over pronto!

MotoSook · 12-31-2002, 01:04 AM

So your mixture setting is rich and you're sputtering when cold, but it all disappears when warm. Could your setting be too rich for your own good? I'm just guessing here so don't yell at me JW.

My guess is that the combination of your rich setting and the WUR's compensation for cold operating condition is causing your problem. I run my 3.0 motor rich (the garage and I smell like it when I'm done playing), but not too rich.

With a 3MM allen wrench try turning the mixture screw counterclockwise an 1/8 of a turn and see if that doesn't fix your problem. Of course a gas analyzer is the only what to do it correctly (had to say it before someone got on me for my bad habits...yes, I carry around a 3MM allen wrench).

Good Luck.

dd74 · 12-31-2002, 01:29 AM

Turn it which direction? Left or right? Remember, I'm not that mechanically inclined, but I am willing to learn.

I sort of know where the screw is, but you can tell me that, too if you don't mind.

Sunroof · 12-31-2002, 04:33 AM

You will need that little 3MM allen wrench to adjust. Any ACE hardware sells them (t-handle); however, you may have to use a hack saw to cut it down to size. ALWAYS carry one in the glove box!

To richen - go clockwise.......................Right -Rich
To lean - go counterclosckwise.........Left -Lean

You will need a CO meter, but I have just experiemented on mine making very slight adjustments (one click at a time by the way) til everything seemed in balance.

Someone put locktite on the adjustment screw, so I was turning nothing for awhile. If you get resistance on the screw, take off the air filter cover and hold the sensor plate with one hand firmly in the up position while adjusting the screw.....

Remember............one click at a time

Regards
Bob
73.5T

MotoSook · 12-31-2002, 08:20 AM

Bob is right about the directions to turn the screw, but I would not buy a T-handled 3MM. The L-shaped 3MM from Sears works better (I have both kinds) without having to cut anything, and it is easier to get in there when you need to. The longer leg of the L-shape is 4 inches or so. The point of acess for the adjustment screw is between the fuel distributor and the rubber boot that joins the sensor plate throat and the throttle body (CIS boot). There may be a rubber plug there.

Your should feel a bit of drag on the screw as you adjust it as the air sensor plate lever is acting on the screw during operation (motor idling).

Make very small adjustments, 1/8 turn at a time. Best to do this while the car is running so you have feed back. I like to idle the motor a bit between adjustments (blip the throttle body from the engine bay). Don't leave the tool in there when you do that as the sensor lever will move on you. It's not a good idea to leave it in there!

The first time you do this you will have to feel around with the end of the 3MM until you find the head of the adj screw. Practice finding it with the motor off. After once or twice, it'll be like scratching the same spot point the back of your head.

dd74 · 12-31-2002, 10:33 AM

Thanks for the feedback, guys. I really appreciate it. Souk: thanks for the image. That really helps.

Rons11 · 02-03-2003, 02:04 AM

Hey Guys,

Just joined the board. I have a 75 911S with similar cold start problems. It always starts right up but in cooler wx it may sputter and spirt a couple of times before running smoothly. It runs great. BTW I have a 3.0 in the car which is a considerable improvement over the 2.7 from my experience.

bigchillcar · bigchillcar's Garage

I have a '74 which runs extremely well in my opinion, but likweise may experience a little sputter for a few minutes while warming after a very cold night. My guess is that is not too uncommon for these older cars built before the time of more sophisticated engine management systems which control more than just spark...i.e. spark, fuel, etc. We're all accustomed to driving newer cars like this at least on occasion and are comparing their more modern 'driveability' characteristics in all weather conditions to cars that are 20-30 years old. In other words, I'm not so certain that there wasn't some degree of what we all experience from these cars even when new.
Ryan