Help diagnose starting problem

[Smurfwarrior911]

It is a cold start problem. It was starting fine before I had some work done to it, however, the rpm's went to 2800 upon start, then eased back down to @ 1000 and started surging from @500 to 1800 and back down again. NOW--- When it is cold.. hit the starter, it starts and goes to @ 2000 rpm, and dies as it sputters around 500...start it again, same thing... after 5 oe 6 of these, the engine is beginning to warm up... starts, goes to 2000, down to idle and sputters like popcorn popping... completley without choke it appears... gradually it starts to level out as it warms up. Hot starts are no problem at all. Engine ran a bit rough until the mixture was adjusted to richer... Vacuum leak?? Ideas?

[T77911S]

maybe this will help you.
there is a big round disk on the back right of the motor, this is called the aux. air valve (AAV). when you start the car, hot or cold, the AAV is open, it lets air bypass around the throttle plate, like holding your foot on the gas when starting it. when it starts, vacuum from the engine closes it and it remains closed while the engine is running. once started, the aux. air REGULATOR (AAR) takes over, but ONLY when cold. it holds the RPM's high for a few minutes when cold. there is 12v going to the AAR to help it warm up, heat from the engine helps to keep it warm. there is a valve inside the AAR that slowly closes as it gets warm bring the RPM's down in a slow manner.
what could be happening is this. the AAV is open and allows the RPM's to rise when started, but the AAR is stuck in the closed position. when the AAV closes, the RPM's drop and the car cuts off. whats strange is that 2000 RPM seems hi for what the AAV would do. but i would first look at the AAR. it is located on the right side of the motor, the thing that gets in the way when changing #6 plug, it has a power connector going to it. take it off and see if it is open.

[Paulporsche]

Check what T77911S said.

Also, check out your warmup regulator (WUR). Your control pressures could be off.

The symptoms you previously had sound like a mixture that is too rich, hence the hunting idle.

Your present symptoms sound like too lean. That's the backfiring, if it is through the intake or airbox popoff valve. Do you have a popoff valve? If there is popping out the exhaust, that usually indicates too rich, although that usually happens on overrun, not idle.

You should search the above terms for more info. Also the Bentley manual has a lot of info on CIS and testing procedures.

Do you have a CIS fuel pressure gauge? This is good for testing the WUR.

You should also verify that all ignition components are functioning correctly.

Has your mixture been changed recently? What work was done to your car?

[stormcrow]

If your engine is surging when cold, it is running too lean, you need to enrich the gas mixture. There is a small pin hole between the intake and throttle body which takes a 3mm allen wrench. Turn it clockwise 1/8 turn ton enrichen the mixture.
Being too lean will also cause backfire which could damage the intake box.

Steve

"A Porsche does more then just go fast in a straight line"

[boyt911sc]

Smuf,

I would like to add one more thing......

....This is according to Ben Watson's book.

Tony