Joe6pack

I have my AFM out of the car. Are there any adjustments or checks that can be done. I confess that I have already removed the cover to see what's inside. Right now, I have it set so that the adjustment screw is all the way in (rich). Anything less than that and I get lugging and it just seems to run better. I am still chasing idle issues.

Thanks,

John

TroyN

I'm sure you explained before but it helps if you list your car in your sig so we know what year, motor, mods, etc. you have. Last I saw you were putting in a new o2 sensor, so that didn't do it?

See here for some AFM info: https://rennlist.com/forums/911-foru...-on-3-2-a.html

whalebird

Search for the uber-easy base idle adjustment for 3.2 carreras. If it doesn't behave right after that, you can look further. I did'nt read the above posted thread, but it is most likely cover in there. Keep us posted.

Joe6pack

Sorry, its a 1987 Carrera 3.2. I am probably being picky at this point, but I still have an idle drop a few seconds after pulling up to a light. The new O2 sensor made a difference in performance. The car pulls great to redline. Unfortunately, the idle drop is still there. I used some alcohol to clean up the traces and some 3 in 1 on the moving parts. I didn't really change anything. I buttoned everything back up, but have not taken the car out for a shakedown. Like I said before, I am probably being really picky at this point.

TroyN

Maybe you can make a little video in the car, put it up on youtube or vimeo and post here so we can see what you're seeing. If you let the car rev down without engaging the idle switch does it have the symptom?

rusnak

We did another thread a few years ago, which involved checking the afm with a 9-volt battery. The cover does not need to come off. The test works very well, and the procedure was borrowed from a 944 guy. Draco was the thread starter. I now have a new AFM that I keep for diagnostic purposes.

Your idle should be very steady. Have you visually checked the operation of the icv? You can warm up the motor, take it out, re-connect, then turn on the key. You should see the servo motors place the valve in the half open position.

dshepp806

Some heartfelt resistance measurements through the resistor sweep would have been good,..at least, to have cleaned the contact area and lube what moves..a good thing....just good to make sure you don't have bad spots on the resitor trace.....this can be adjusted for via wiper arm repositioning.....

Whatever you do,..don't touch that spring!!!!!!!!!!
Doyle

Ed Hughes

It seems we recommended checking and cleaning the ICV to someone recently- was that you? Have you looked at your ICV? It could be the culprit. Do you have any intake/vacuum leaks? Another source for a quick drop in idle at a stoplight.

rusnak

Vacuum leaks would also cause an oscillating idle.

Joe6pack

Thanks all. This isn't really an oscillating idle problem it is consistent behavior that i have been dealing with. Sorry to start another thread on this. I did do some resistance checks on the pins as I opened and closed the damper. pin 1 to pin 3 was about 100 ohms sweeping to a peak of about 1400 ohms a little past half open and then to 600 ohms full open. Pin 2 to pin 3 was exactly the opposite. 600 to 1400 to 100. I figured it was too consistent not to be correct. I am pretty sure I was on the 2000 ohm scale. Hope this makes sense. I am going off memory and wish I had written everything down.

As stated before, I have the adjustment screw to full rich. The new O2 sensor reads about 0.1 VDC. When I open the throttle, the reading jumps to about 0.4 to 0.6. I also get a little popping in the exhaust at idle and I think it is lean. I don't smell raw fuel. Off idle everything is great - strong, smooth with no hesitation at all. It has a new fuel filter, CHT sensor, cap, rotor, coil, plugs and O2 sensor. I noticed that there was a wheel in side the afm that looked it could be used for course adjustment. I didn't mess with it.

I think a video is in order. Stay tuned.

rusnak

Here's the aforementioned thread. Don't do what I did, and read the afm pins upside down. That makes for some interesting results until you go "duh!" and flip it right side up.

https://rennlist.com/forums/911-foru...hlight=944+afm

You have to connect power to the afm, and then take voltage readings. Resistance alone is futile (sorry, that was bad).

dshepp806

I used a good old analog meter to watch the resistance measurements.

Joe6pack

Ok - Here are a three videos I shot this morning showing my problem. As you can see, this is an easy problem to repeat, but difficult to diagnose. Each video was shot after coming to a stop after 2-3 minutes of driving. When I pull up to lights, I'm always betting with myself about whether the light will change before the idle drops. I can't tell you how much this annoys me. Otherwise, the car runs great.

http://www.youtube.com/watch?v=3RdCB6Q4Qok

http://www.youtube.com/watch?v=aRPT66wezA4

http://www.youtube.com/watch?v=Z8bP_hpaLgA

rusnak

Have you checked for manifold leaks, or the little hose going to the ambient air valve, and the crankcase breather hoses? It looks like there could be a vacuum leak or something, then the dme is compensating.

Joe6pack

I have checked for leaks and I have had a pro check for leaks - none found.