nikkoa

So i have done enough research on the 911 to know the CIS is far from flawless, but i suspect more is to blame here. The problem (IMO) is getting progressively worse. I shall outline some problems I've noticed, please enlighten me with any similar issues you have had and solved!

-Hard start when cold
-When started (after several attempts) white smoke is ejected from tailpipe for 10-30 seconds, motor hardly runs initially
-Car dies on idle
-Hesitation under light load
-Car runs smoothly once warm

As a few of you may already know i have 2 broken headstuds and chamber 4 is at a 15-20% leak. I did test the thermo switch with the CSV to see if that was the problem, but the test light was 'on' so i guess it's not faulty? What surprised me most when i unplugged the thermo switch the CSV test light still came on, maybe i wasn't testing correctly. Anyways, all signs point to the Control Pressure Regulator but i would like to be sure.

whalebird

You could have nailed it with a control pressure regulatr. I belive this is sometimes called a warm up regulator. Do you have the "toilet seat" in the air box? Also check the airbox for leaks/cracks. Does the car backfire/sputter once started? Your tech should be able to put fuel pressure gages on it and check your pressures. The fuel pressure accumulator can cause problems as well. There are other possabilities, but start with these.

nikkoa

Thanks whalebird. Yes my car does in fact sputter/backfire once started. Sounds like i need to hook it up to a fuel pressure gauge ASAP, before i go replacing any parts. I've check the airbox for leaks but the boot on top is quite old and is probably in need of replacement.

whalebird

It takes some special gauges. The gauge is "T-ed" into a hose that goes between the warm up reg. and the CIS fuel distributor. Then different test can be done by switching a valve between the supply pressure and control pressure. CIS is an easily diagnosed system and very reliable. If the fuel pressures fall into spec, then there could be other problems still. Check the fuel first. If there are any notable mods to the car let us know. Also some past history of service/repairs may help narrow the problem a bit.
A broken airbox (from intake backfire) can be difficult to see and makes the car run awful. Does your car have a pop of valve(toilet seat) installed under the air filter?

Peter Zimmermann

There is one other possibility. The OXS relay under the passenger seat might be defective, causing the frequency valve to not work. Remove the air filter and cover, turn on the ignition, and briefly lift the sensor plate arm about 10mm. You should hear a distinct, even loud, buzzing noise from a device (the frequency valve) just forward of the throttle body. No noise? The relay, about 1" square and silver in color, located near the center tunnel under the passenger side front seat has probably failed. It has a quick disconnect harness and a clip that fastens it to a small mounting point. Relay part # 821 951 253.

nikkoa

Ahhh tricky stuff Pete. I was wondering what that box did! As a matter of fact, i do recall placing my hand inside of the airbox with the ignition turned and hearing that noise. I will confirm though seeing how it can easily have a short or the likes.

Whalebird, i do have the pop off valve added. I'm thinking that whatever is wrong with the system is a fundamental component seeing how the car can hardly stay running while cold.

One thing in specific that bothers me, while im accelerating the RPMs like to 'bounce' so to speak. Even when my foot is locked on the gas, the engine likes to pulsate lightly forcing me to engage the clutch or give it more gas. Anyways im somewhat certain all of these problems are tied to one specific part!

Appreciate the help guys. Somewhere to start for sure!

Peter Zimmermann

By the way, your symptoms are exactly those of a failed frequency valve/OXS relay...

nikkoa

Got everything back in the car. Its been 600 miles. Still some cold start problems. I think its a vacuum problem. I have replaced the cold start valve and the OXS relay with no improvements.

A list of problems:

• When warm the car runs at 850-900rpm steady and responsive.
• The car cold starts at 1000rpm, drops to 500 then bounces up and down for moments or until it settles again at 500 rpm. It runs at a constant 500rpm until the engine is hot.
• Slight sputter when given gas on cold start.
• When warm it purrrs

theiceman

do nothing else until you have your control presure checked

nikkoa

I havent had time to check the control pressure yet but....

When the car starts and is bouncing between 500-1000 rmp the headlights get brighter then dim. Could this be an electrical problem?

Also when i rev the engine the headlights get brighter...

theiceman

check the other thread on SC starting to look at electrical issues. lthough this may be more os a symtom of the car iding at 500rpmand the alternator not running at fulloutput more than anything. But definitely worth a check.