Originally Posted by BMEPdoc (Post 5802661)

I wholeheartedly agree with Paul's post. Pay particularly close attention to the auxilliary air valve. These motors are set-up relatively lean and it doesn't take much of a vacuum leak to rob the sensor plate on the fuel distributor of the vacuum required to move the necessary amount in order to run properly. The AAR is notorious for causing the problem you describe making the motor either hunt up and down in RPM or simply die shortly after firing when cold, many times with a pop or backfire though not always.

In simple terms, the AAR is a temperature controlled (via the thermo-time switch) vacuum leak which, in conjunction with a richer, cold start mixture provided by a properly functioning FPR allows a marginally higher cold engine RPM until stabilizing to an even, lower, warm idle. If ANY component in the system is out of operational specification, a running issue exists. If, for example, your cold control pressure is too high (lean) then pops backfires are the result. On the other hand, IF you have a vacuum leak somewhere, control pressures are superfluous as a main component (air flow sensor) isn't receiving it's proper operating orders to begin with.

Also, by now, I'd imagine the majority of CIS cars out there have the toilet seat or backfire valve fitted. With the air filter cartridge removed you'll see what looks like a... well, spring loaded toilet seat epoxied to the floor of the housing. These were fitted specifically due to the propensity for the motors to cough or backfire as a result of their lean settings (particularly when ALL vacuum related components don't function as absolutely required), leading to warpage and in some cases just flat out blown up air boxes. You may want to check see that there aren't any issues there with a piece of debris or some such thing keeping the flap from sealing properly. There was even an outfit years ago which made cast aluminum air boxes to address this issue, though, I feel the toilet seat solution is more than adequate.

Also, it goes without saying. Your system control pressures MUST be with a given range of operation from cold to hot. If you don't have the gauges to verify the FPR or fuel pressure regulator is within specifcation, then you can very well be on a not-so-merry-go-round. Still:

Remember, air leaks are the enemy to a CIS system. That means anywhere a vacuum leak can occur. Injector seals, distributor vacuum diaphragms, etc. You can clamp a small pair of vice grips with which you can pinch off the vacuum line leading to the AAR to determine if it's the offender, or have a friend use pliers to selectively pinch off the lines. When you finally do get it to run, and once you get the motor up to operating temp, you can then use a can of carb cleaner and squirt a brief spray at the base of the manifold leading to the heads and check to verify the condition of the gaskets as well as where the injectors fit into manifold to determine the condition of the seals. Again, anywhere in the intake flow path. If you discover any notable change in RPM, address the seal or gasket or component.

Good luck

regards,
Jozef Schumann

Originally Posted by boyt911sc (Post 5803409)

Jozef,

AAR (auxiliary air regular) and TTS (thermo-time switch) are not even remotely related to each other. In fact they have nothing to do with others functionality and not even closely located in the same electrical circuit. Are you sure of this? Please inform us.

Tony

Originally Posted by psalt (Post 5803711)

Tony,

Yes, I was right, hopeless. Your record of misreading and misinterpreting my posts and responding with incorrect personal attacks is intact. Anyone with actual experience diagnosing a running " later lambda system " would know there are two ECUs and a relay with 23 connected pins. But, I guess it is pretty clear that you have no experience with them. Have fun with your boxes, perhaps you can take a photo of them to add to your posts and pretend that you know what they do.

Originally Posted by psalt (Post 5756640)

Paul, I have to confess I don't know what MY is and the other stuff makes even less sense to me.
Could you please elaborate?
Remember, mine is a 1982 911.


Warren

MY is model year, as in 1982. Your car's engine has the second version of CIS lambda. The first version in MY 1980 had a different calibration and several drivability issues, which were addressed in the later versions with band aid solutions until the EFI system arrived. If you think that your car has a cold acceleration problem and you are unaware that your engine has a separate cold acceleration control unit, my advice would be to take it to someone who understands the system or start studying until you understand the two dozen circuits of the control units. CIS lambda is very different than the basic system, corrects pressures are not "good enough" for good running. However, the system can be diagnosed with a dwell meter by someone who understands what they are doing. Swapping parts or altering pressures are a dead end until you know that all the system's functions are working as designed. My experience is most of the cold running issues on CIS lambda SC's have nothing to do with the WUR.

Originally Posted by scott.k (Post 5841629)

When I run the car, I start it and it goes into a 400rpm choppy idle, and dies out after about 5-10 seconds unless i hold thi little lever in the air box and move it up and down as necessary. When I do this, i can keep it running pretty smoothly for about two minutes. I did have the car running since I started this thread but since then, i put a bit too much oil in and thats when it started backfiring and couldnt stay running so I drained some oil and i havent got it running well since then. Could it be that I need to adjust the air/fuel ratio, or some adjustment like that?
Thanks
Scott

Originally Posted by scott.k (Post 5841721)

I can get it to run great at about 1500 rpms if i hold the lever in the air box up.

Originally Posted by boyt911sc (Post 5841770)

Scott,

By lifting the lever up, you are injecting extra fuel to compensate for the unmetered air!!!!! Pressure test your system to locate the air leak. Adjusting your fuel mixture without fixing the vacuum leak will make a bad situation worst. Problem like this will not go away and you need to approach it with a positive attitude. The vacuum leak might be right in front of your (my) nose but might not be obvious. In lieu of a smoke machine, a low pressurized air (5 to 8 psi) is sufficient to expose the leak/s.

If the test will show that there is no existing air leak in the system, then you have eliminated one critical variable in the equation. HTH.

Tony

Originally Posted by boyt911sc (Post 5842536)

Scott,

If I'll be doing the troubleshooting, I would do the following:

1). Inspect and confirm that all the vacuum lines/hoses are attached or connected properly as per vacuum diagram for your engine. Check clamps, cracks on hoses, etc. You might have a vacuum line inadvertently connected to an atmospheric outlet.

2). Check your fuel pressures (control, system and residual). By doing this, you would know more about your WUR, FD, FP & fuel accumulator without even running the engine. This is a basic CIS troubleshooting procedure that you should implement. If you are not familiar with this specific procedure, let us know and we'll lay out the step by step procedures for you. If the fuel pressures are within spec, you have reduced the variables to be able to do a meaningful investigation.

3). Ignition timing & sparks including a fully charge battery must be checked and confirmed too.

In your earlier post, you mentioned that you were able to run the engine briefly for several seconds by manipulating the AFS (air flow sensor) lever. Unassisted, the motor failed to run at all as per your info. So it's time to stop guessing and do another test.

4). Perform a vacuum or air leak test. It would only take a minute or two to confirm and verify the integrity of your vacuum system. The test will show you whether it is leaking or not. It would most likely show some air leak/s!!!!! The big question is how severe is the leak to prevent complete engine combustion (????). If the test result is negative, which I doubt, re-direct the investigation to pin point the culprit/s.

Your problem is not difficult to fix. Keep us posted.

Tony

Originally Posted by Bob Kontak (Post 5842553)

Tony - How do you perform the pressure test you speak (and have spoken) of? I have rigged maybe 10psi air pressure to the air box with duct tape and sealed off the exhaust and wet my hands feeling for air leaks. Only really find big leaks that way

What is your pressure test.