Help! Problem with my 1983 911SC

[bxtech]

Hello all,

I am having some trouble with my 1983 911SC. It starts right up when cold and runs good. However, if you touch the accelerator at all when it's still cold and is warming up, the engine hesitates, coughs and starts "popping" inside the airbox badly. It idles fine when it is cold. Once it's all warmed up, the car idles and and revs up fine (with no load).

Now, when the engine is all warmed up and I take it for a drive, this is what happens: When you first start out in first gear, the car accelerates pretty rough and feels almost like it is running out of fuel. You can feel the engine hesitating and running rough and there is not a lot of power. In any gear it gets the same symptoms, so it's definitely an engine problem. However, once you step on it and the RPM's get above 3500, the car smooths out and takes off! It runs MUCH better anywhere above 3500 RPM. However, even at the top end, there's not a whole lot of power like there should be. When you floor it (even above 3500 RPM), the car doesn't accelerate like it should. The engine always idles well and it never dies.

The car has been serviced recently which included: new warm-up regulator, valve adjustment, spark plugs, new distributor cap/rotor.

I am thinking that this could be a fuel delivery related problem? Maybe a bad fuel accumulator? Dirty injectors? Problem with the injection sensor plate? I had another 911 with a fuel flow problem, but all of the symptoms were at higher RPMs and at highway speeds. This car is totally opposite. Any ideas, personal experience and/or suggestions on this problem would be greatly appreciated!

Thanks in advance!

[Superman]

Verify proper ignition operation first. Once you have verified this, then look toward the fuel system.

There is no substitute for following the CIS troubleshooting procedures. Well, actually, there is a substitute. You can guess at the problem and swap parts until you guess correctly. This method is SUBSTANTIALLY more expensive and takes months longer than the troubleshooting procedures. They involve stuff like verifying system and control pressures, and making sure the air flow sensor plate position is properly adjusted.

[DaddyGlenn]

Originally Posted by Superman

Verify proper ignition operation first. Once you have verified this, then look toward the fuel system.

There is no substitute for following the CIS troubleshooting procedures. Well, actually, there is a substitute. You can guess at the problem and swap parts until you guess correctly. This method is SUBSTANTIALLY more expensive and takes months longer than the troubleshooting procedures. They involve stuff like verifying system and control pressures, and making sure the air flow sensor plate position is properly adjusted.

+1

Verify the ignition is set correctly, then step through the CIS troubleshooting part of your Bentley Manual. (You do have the manual don't you?)

There are so many possibilities, a disciplined, step-by-step approach is your best bet.

[Jim Williams]

+ 1 to all the suggestions to take a structured approach to finding the problem. The '80 - '83 CIS is a little more of a challenge than the earlier versions due to the Lambda system. There is a significant amount of info on my website on the CIS, including a few suggestions on what to do first when troubleshooting. First, it takes some understanding of how it all works to do a credible job with finding problems.

If you want to do this troubleshooting on your own, you should consider a pressure gauge for checking system pressure and control pressures. The symptoms you describe could be due to an improperly operating Lambda system, as it provides enrichment to the engine on acceleration where you seem to be having problems, as well as functioning with the O2 sensor to provide the best mixture for the Cat.

CIS Website : http://members.rennlist.com/jimwms/CIS/CIShome.html

[cab83_750]

I am no expert, but when I serviced my '83 some time ago, I inadvertently installed the spark plug wires 'clockwise' and had some of your symptoms.

Check if they are installed counterclockwise. This should be the easiest first step you could take.

Good luck!

[fred cook]

With the car in a dark place (preferably at night) start the engine and look for blue-white "lightning bolts" flashing from the plug wires to a nearby ground. It sounds like you might have a bad coil wire or plug wires.

Hope this helps.

[Maxx1]

I had some really weird problems with a Permatune ignition module after my car warmed up .... I don't know if yours is Bosche or what, but maybe that is something to look at.