And one more: IDLE - Video

[Simon930Berlin]

Hi,

engine cold, just started.

930 bad cold idle - YouTube

This is not 100% regular behavior. Some times it just hold idle, after revving for about 20 seconds at 1.5K, and then dropping to 950 sharp.

When warm, from 180F onwards, it idles at 950, too.

?

Where should I be looking? The vacuum system looks fine, but is there a way to test it?

THX
Simon

[Simon930Berlin]

Is it so obvious, it doesnt deserve an answer?

[zcoker]

Try adjusting the idle screw on the throttle body. Works wonders.

[911nut]

It could be (1) cold control pressure incorrect, or (2) cold start injector is not operating.

[pkracer21j]

auxiliary air valve stuck closed?

[mark houghton]

I don't understand your issue. Is it that after a short revving, it drops way down to 200 rpms and then recovers back to 950?

[Simon930Berlin]

Yes Mark! In rare circumstances the engine dies, because it dropped too low. Even in this clip you can see the red light coming on, close to shutting down..

[flat_6]

I have been trying to find the same issue with mine. When warm it idles perfect but when its a true cold start my idle can be 200-400 rpm and bouncing. I have confirmed by cold control pressure to be correct and I watched the AAV closed and open with the supplied voltage. Could it be the cold start injector??

Sorry Simon930Berlin, I am not trying to hyjack your thread. Sounds like we have the exact same issue.

[mark houghton]

Even with proper control pressures and properly acting AAR, if you don't have your idle mixture set correctly then you could see those symptoms. You're either too lean or too rich at idle.

Get the car fully warmed up and try adjusting the mixture (4mm allen wrench, push down the spring loaded adjusting screw until it engages) and turn it slightly clockwise to richen or the opposite direction to lean out. See what it does to your idle, stab the throttle and see how she responds. I'm thinking you're a tad too rich (but it's early in the morning and my brain may be working backwords). Very small adjustments to that screw....just a degree or two at a time, and remember where you started at.

Once the mix is set correctly and your symptoms go away, finish the tune with the idle speed adjustment screw.

[flat_6]

Funny you mention that as I reset the idle yesterday. Car was fully warmed up, running 10deg BTDC at idle, adjusted idle screw to get 1000 +/- 50 rpm (as per MSD). I then adjusted the mixture to get 13.5 AFR on my innovate MTX-L.
What am I doing wrong??

[JFairman]

Looks like it's running a little on the rich side at idle because of how it drops below idle speed and comes back up after small throttle blips.
I think you said it idles where you want it once everything is at operating temperature.
From the little we can see of the oil temp gauge it isn't fully warmed up yet and the cold start aux air valve has probably closed so it's not bypassing air around the throttle body to keep idle up.
It's possible that the warm up part of the control pressure regulator hasn't warmed up all the way and thats causing the slightly rich mixture for a few more minutes or until the motor fully warms up.

There is no computer controlled idle control valve bypassing air around the closed throttle butterfly in CIS to maintain a steady controlled idle speed like motronic has so CIS will never have a perfect idle speed during engine warm up every time you start it.
It's all typical old CIS that's a little out of adjustment.

If your car is a mid eightees car with the vacuum solenoid that blocks intake manifold vacuum from reaching the vacuum retard pot on the distributor for the first couple minutes after a cold start it's possible thats not working right either.

[Simon930Berlin]

Thanks, guys!

mine is a 77 3.0, so I am not sure how the vacuum system is set up.
All I know is, I know too little. Is there a good write up somewhere, that explains?

Also, is there a kit for checking AFR somewhere on Pelican, so I can properly test my setup? Whats the right tool to get?

[flat_6]

I looked into all the AFR devices out there over a year ago and chose the Innovate MTX-L and have been very happy with it. Here is a link
MTX-L Wideband O2 Digital Air/fuel Ratio Gauge

[Simon930Berlin]

Flat_6, those guys even have an obd-II to iphone setup, I'll get that for my e60 M5
Thanks for the tip..

In terms of checking AFR, on a 3.0 turbo, can I check it all without a dyno, standing in the shop and revving, or does it have to be in gear?

Feel a little dumb here, but it feels as if the turbo spools, but doesnt push air in the engine when not in gear and just revved?

[flat_6]

Simon930Berlin, you need to check your AFR when driving so the car is under load. You can plug the Innovate into a laptop and log it through there or try to watch it (not easy to do).