Extreme Lean Condition / Power Loss at 5500

[John Brandt]

The Full Throttle switch is adjustable...Even if the switch is working it needs to fire at the right time. It rotates or pivots on two small screw axes. Check to see that they are in adjustment and tight. If the switch doesn't activate at those high rpm's you get exactly the scenario you just described.

[flyingplatypus]

Update. So, I opened up the AFM and I'm pretty sure it was tightened up. I don't have a stock one to reference, but it felt pretty difficult to open up the air flap. Upon further inspection I found that two of the teeth on the spring apparatus had a white mark of paint between them. I am assuming that someone had tightened it and left this mark as a reference point if someone wanted to put it back. I sealed everything up and put it back, started up the car and it had a tough time hunting for idle, but it eventually settled. I had to leave for the airport before I had a chance to actually drive it. I will update again after I drive it to make sure everything is fixed.

Thanks everyone for the help!

[flyingplatypus]

Update 2: There seems to be more power and the flat spot of power is gone, but now the idle is terrible. It hunts like crazy and dies when clutching sometimes if it evens out it idles at 1000 instead of 800 like it was before. What do i need to do to fix the idle?

Thanks!

[ischmitz]

You need to adjust the bypass screw on the AFM. It essentially sets the flapper door position (mixture) at idle. If you let a lot of air bypass the mixture gets leaner because most air doesn't pass through the flapper. If you close the screw the mixture gets richer because more air goes through the flapper.

Remember, the amount of air (metered + unmered) is set by the throttle stop position and not by the bypass screw.

Assuming you loosened the main spring in the AFM you most likely have a richer mixture during idle now with the same air flow pushing the flapper door a little more open. To remedy open the bypass screw by a couple of turns. Remember where you came from so you can alway come back. I believe the default setting is something like tighten it all the way and then back it out by three to four turns. Best if you had a wide-band O2 sensor to properly set mixture during idle.

ingo

[flyingplatypus]

Originally Posted by ischmitz

You need to adjust the bypass screw on the AFM. It essentially sets the flapper door position (mixture) at idle. If you let a lot of air bypass the mixture gets leaner because most air doesn't pass through the flapper. If you close the screw the mixture gets richer because more air goes through the flapper.

Remember, the amount of air (metered + unmered) is set by the throttle stop position and not by the bypass screw.

Assuming you loosened the main spring in the AFM you most likely have a richer mixture during idle now with the same air flow pushing the flapper door a little more open. To remedy open the bypass screw by a couple of turns. Remember where you came from so you can alway come back. I believe the default setting is something like tighten it all the way and then back it out by three to four turns. Best if you had a wide-band O2 sensor to properly set mixture during idle.

ingo

That makes sense. I will try that out. Where, exactly, is the screw located? Do I need to remove the AFM again?

[ChrisBennet]

In case someone else comes across this thread with a lean-at-the-top RPM problem; there is another (unlikely) possibility:

If the fuel tank isn't venting properly you can get a lean problem at high RPM's. If the tank can't suck enough air in to replace the fuel it pumps out, a vacuum results that will reduce the ability to pump fuel.

If you hear a "whoosh" of air when you unscrew your gas cap, your tank isn't venting enough. At lower RPM's the fuel pump can keep up so you might not have any troubles until you get to the track.

Don't ask me how I know this...

[ischmitz]

See here where the blue arrow points. Sometimes the access hole is covered with a blue plastic cover. You can pull that cover out with a sharp pointed tool. If the cover is gone you should get to it with the AFM in the car.

The screw is 3mm or 4mm HEX socket - don't remember on top of my head.

(curtesy of FRWilke)

[flyingplatypus]

Originally Posted by ischmitz

See here where the blue arrow points. Sometimes the access hole is covered with a blue plastic cover. You can pull that cover out with a sharp pointed tool. If the cover is gone you should get to it with the AFM in the car.

The screw is 3mm or 4mm HEX socket - don't remember on top of my head.

(curtesy of FRWilke)

Perfect. I will lean it out and report back.

[flyingplatypus]

I wasn't able to get the car to stop hunting. Is there a way to measure the CO using the O2 sensor? I have a pretty decent multimeter.

[john walker's workshop]

is the closed throttle micro-switch getting closed? should hear it click quietly as the throttle closes and opens.

[flyingplatypus]

Originally Posted by john walker's workshop

is the closed throttle micro-switch getting closed? should hear it click quietly as the throttle closes and opens.

No problem with the microswitch.

[flyingplatypus]

Hey Everyone,

Another update. So I took the car to the dyno again and loosened the AFM until the AFR stayed between 12.5 and 13.5 during a full pull. AWESOME. But, now the car won't lean out during idle. I think that when they tightened the spring that they messed with the bypass adjustment. Even when I pulled the screw out completely it was still running rich. Could someone have disabled the bypass completely? How would I be able to tell if this is what happened?

Thanks!
Justin

[flyingplatypus]

I pulled the AFM off again and checked if air was flowing through the bypass by running a bit of water down it, it appears to be working.

[flyingplatypus]

Here are the new dyno charts with the AFM placed in the correct position.


Compared to Original:



Here is a photo of the AFM internals:


As you can see, there is a white mark(i moved it one click leaner so it is easier to see) that I placed the AFM for the new runs. Even though that is where its supposed to be, did I make it too rich?

[Steve W]

Your full throttle AFRs look a lot better after, and the power of 207rw is good. But the AFM is a triple tip version with the additional ground wire, usually found on the 964s and rarely on the 3.2s. Not sure on if and what difference in calibration between the 964 vs the 3.2 meters are, but that could explain your problem with adjusting idle. You could try repositioning the copper sweep arm a bit more clockwise by loosening the philips screw to reduce idle voltage output, but you might need to readjust your clock spring again.

[flyingplatypus]

Originally Posted by Steve W

Your full throttle AFRs look a lot better after, and the power of 207rw is good. But the AFM is a triple tip version with the additional ground wire, usually found on the 964s and rarely on the 3.2s. Not sure on if and what difference in calibration between the 964 vs the 3.2 meters are, but that could explain your problem with adjusting idle. You could try repositioning the copper sweep arm a bit more clockwise by loosening the philips screw to reduce idle voltage output, but you might need to readjust your clock spring again.

Well, it sounds like that explains it. If I adjust it to the point where it idles correctly, would I be able to get a custom chip burnt?

[Steve W]

shouldn't be a problem with good accurate data