More in depth CIS diagnostics and SSI install

[JSZ]

After having some issues with my stock 82, 911 engine, predominately with the CIS system, I decided to drop the engine and test it where I could get at all the components. I was having high idle issues, 1800-2000 rpm and some very minor hesitation in the 2500 rpm’s. Also, I intend to install a set of SSI’s on it so what better time to do that
Car and engine background, low mileage car that sat for many years with broken head studs. A top end rebuild and reseal was preformed.

Here is an outline of the tests and findings.

Smoke test of the vacuum system: I injected the smoke and air at the brake booster connection in the engine compartment. About 1 psi was used with the smoke. Immediately smoke started coming out of the blue vacuum line at the throttle body connection, actually it was split wide open there. A few pin hole leaks were faintly detected on the air box bottom plenum seam, so decided to remove and further test. No other vacuum leaks were detected.

Air Box immersion test: I sealed all the ports to the bottom plenum and installed a shrader valve in the throttle body seal then 4 to 5psi was injected into the lower plenum and submerged into a tank with water. Two areas were noted that had very minor air bubbles coming from the seam. These areas were “V” ground with a tapered bit and injected with an epoxy where the groove was cut in.

Throttle Switch, left rear: Found it was not closing at idle, switch is good though will require minor adjustment.

Vacuum Testing of the AAV and DV: Auxiliary air valve was removed and vacuum applied, at about 8” of vacuum slowly dropped. I understand this is acceptable. Deceleration Valve, at about 16” of vacuum on the small line, the large port would open and allow passage of air. I believe the DV spec should be 17” of vacuum. I understand Porsche issued a bulletin to crush, so to speak, the DV to increase the large port opening at a higher vacuum. I still have not found the Porsche bulletin, though I have seen it. So I am treating this as an issue to resolve.

AAR Testing: Auxiliary Air Regulator was removed and visually inspected. Body temperature was 74 degrees, and the opening was approximately 70% closed. I then added 12v power to the electrical connector. At 3 minutes, door was approximately 90% closed, 5 minutes it was at 99%. At 5 minutes and 30 seconds it was fully closed. I then place the AAR outside in 10 degrees for an hour and retrieved. The body temperature was 32 degrees and the door was open at 50%. I believe the AAR is in working order.

Car Body Vacuum Tested to Brake Booster: I applied 20” of vacuum on it for 10 minutes. In 10 minutes it lost 1” of vacuum. Based on the minor loss and time this is acceptable.

All Vacuum Lines, Vacuum Tested: All the larger lines were fine. Smaller lines I am replacing.

Fuel Regulator and WUR: both have been recently rebuilt and calibrated by Tony. The SP and CP are within spec.

In addition to the CIS system, I have a suspicion the distributor and Lambda system will require some review. The frequency valve was tested in the past, and had the proper ohm rating, however it did not seem to be vibrating. So I am either going to send the Lambda ECU out for testing or try to find a known working one to replace it with. O2 sensor is new.

On the distributor, I am going to remove clean and inspect it. I have tested the vacuum and both the advance and retard hold. I have also checked the side to side shaft runout and I have 0.009” and vertical shaft movement of 0.035”. I suspect the distributor has had little to no service. Trying to get up to speed on disassembly and assembly of the distributor.

Anything else I am missing for testing? Input much appreciated.

Lastly, I have two questions on the SSI install, one, I am also running a wide band O2 sensor, (AFR). Can I install the bung on the right collector tube? Thinking it will be less congested then the left exchanger with the O2 sensor. Also there is a tab on each heat exchanger that appears to mount on the underside of the engine case. The casting nub is there on the engine case, however it is not drilled and tapped. Can I leave it without the mount attached or do I need to drill and tap?

Thanks for all the help and input, past and present.

[wreckah]

while testing the AAR: yes the port looks closed 100% visually, but make sure no air can pass through when it looks closed.

SSI: yep, couple of little flanges have no corresponding mounting holes...no issue.

frequency valve not working could be as simple as the FV relay that is broken. cheap and easy to check.

[T77911S]

GREAT JOB!!!
that's what I like to see when people test their CIS.

hi idle and 2500 RPM stumble seem to be a quite popular issue.

I you might consider just replacing the rubber boots on the intake runners and maybe the injector sleeves and Orings.

I would also adjust the valves while it is out.

the DV can cause the hi idle.
its not a big deal if it is not 100% closed. 99 is fine.

again, great work.

[JSZ]

Thanks for the advice and will follow up on the fuel injector sleeve "O" ring replacement as well as replace the injector "O" rings also. Intake runner boots were changed during the rebuild process. Injector sleeves, just press in with lube in a thoroughly cleaned sleeve port? Any other thoughts on securing them? According to the tech article, no.

Will get to the valves also.

Have found the Porsche recommendation for adjusting the deceleration valve. I have proceeded to squeeze it the 1mm and now have and opening vacuum of 18.5", in lieu of 16" or so.

The speedometer boot was damaged previously, can I just replace the boot with out buying the complete electronic assembly?

Thanks again, Jeff

[spoke]

My '86 930 with CIS had developed high idle. While running, the AAR hose was clamped off and the idle dropped significantly. I bench tested the AAR and it opened and closed as expected.

Put the AAR back on the car and tested the voltage to it: 0V. AAR is on the same circuit as one of the fuel pumps which are controlled by a relay in the front fuse box. Opened the fuse box to find a relay laying in the cover. Plugged it back in and the high idle disappeared and the engine ran much better.

[pmax]

Hesitation at 2500 rpm is independent of speed ?