Interesting CIS Issue - Clutch in stall

[T77911S]

you want around 14.7 at cruise.
set it for what ever JW said.

I did not scroll back up to look, how are you measuring AFR's now

[sigchuck]

Curiosity and impatience got the better of me before the AFR analyzer arrived, so last night I decided to try my hand at the sensor plate mixture setting technique described on the cis911primer.com website.

On initial check, it was definitely running rich. I ended up turning almost a full half turn before I got to the "it might be just about right" behavior described on the website. I adjusted the warm idle to around 1k RPM and went for a fairly lengthy test drive. The problem appears to be gone for the most part, but RPMs still drop below idle speed on clutch-in, just not anywhere close to stalling the engine.

What is normal behavior at clutch-in to neutral on a CIS 911 that's functioning 100% properly? I do still plan to use the AFR meter to fine tune when it arrives.

Also, a warm idle hunting issue appears to be gone based on last night's test drive and my drive to work this morning. Last night while sitting in the driveway after returning home, the idle would go from around 1k to 1250 then back to 1k. This wasn't what I would describe as "hunting', but rather seemed almost intentional. Any thoughts?

Some additional information: The shop that rebuilt the engine has an extremely good national reputation, and is particularly popular in the southeast and Texas for their in-house machine work. That being said, I think they do quite a bit more race engine work than perhaps tuning antiquated CIS systems. I think it's possible that after the engine was rebuilt the CIS was simply bolted back on (with new vacuum hoses) as it was "running fine" prior to the rebuild, aside from the collapsed tensioner that necessitated the rebuild. I'm still not sure why the rich running issue would have suddenly presented itself though. Maybe something to do with the high temperatures we've had in Texas, or maybe the break-in process reached some point where it became more obvious? All just guesses.

Thanks again for all the help.

[T77911S]

i asked about surging back in post 2.

BTW, I never used an O2 analyzer when tuning my 77s. I kept going richer until the RPMS would dipped down when releasing the throttle or it would surge, then I would lean it out until it would not do either one.
when I did get an analyzer the mixture was always good. it really did not matter because it ran so well how I had it set.

so no, it should not dip down when you release the throttle. just blip the throttle and let the RPM drop, lean it until it no longer dips down.

I also had my DV bypassed., hated that thing.

[sigchuck]

Sorry I missed the surging question. I think there may still be some issues to sort out elsewhere in the system and I still haven't received the gauge kit so I can't yet baseline fuel pressures.

Another thought is that since the O2 sensor was disconnected at some point that the mixture was enriched to compensate for that fact on cold start. Please excuse me if I'm getting this wrong, but I think I understand that the WUR takes it's enrichment directions from the lambda system on lambda equipped cars. Since mine has the 02 sensor disconnected (even though the ECU is still connected), maybe this would have some effect?

[pmax]

Originally Posted by sigchuck

Another thought is that since the O2 sensor was disconnected at some point that the mixture was enriched to compensate for that fact on cold start. Please excuse me if I'm getting this wrong, but I think I understand that the WUR takes it's enrichment directions from the lambda system on lambda equipped cars. Since mine has the 02 sensor disconnected (even though the ECU is still connected), maybe this would have some effect?

The Lambda system does not control the WUR. It tunes the fuel pressure by modulating the FV's duty cycle based on the O2 signal. If you have the O2 disconnected, the system defaults to a fixed 50%.