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tii mix problem

Guest Anonymous

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Guest Anonymous

First the facts

rebuilt pump is b1

head is e12

new warmup regulator, injectors, rubber hoses, linkages (adjusted correctly)

timing is dead on, points gap at .016 (dwell meter busted)

new w7 plugs

new cap wires rotor condenser

new stock coil

With the idle mixture set at 2-3% it runs super lean at 3000 rpm. First I thought that the co meter was not working properly as it is old. When I adjusted a rich idle still it ran under 1% at 3000 rpm. So I went out for a few runs to check mix at the plugs under load. White- so I continued to back off the butterfly to richen the mix. 4 runs like this and backed out the mixture further each time- still lean.

Pull back into the garage and check the co meter at idle- 11%. Way too rich. After running at idle for a minute or so the plugs are grey (white on the way to black.) So I figure possible vacuum leak. But I haven't found anything there yet. Also it seems that a vacuum leak would strongly affect the idle mix.

I also thought that possibly the fuel pump is weak- however I had tested it before putting it in. It pumped the correct quantity per minute.

Any ideas about what is going on here. Is there any way to affect the mix at one level without affecting the mix at another? I have not adjusted the mix at the pump at all. I have only made adjustments at the throttle body.

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Guest Anonymous

If you open the tuna can the butterfly is moved on a

cam, there is small screw that adjust the linkage

position relative to the cam. The problem is that

the cam is relative flat at idle, so there is a lot more

room for error on that side but no so much on the

3000 rpm side. That said, and I realized I really

don't know enough on the subject, there is a good

section on the yellow BMW enthusiast companion

book, that actually goes thru the process of

adjusting the tuna can. I've tried it and it works!

There are at least 5 other methods, and they all

seem to work as well, but the this one is the

simplest and you don't need any special tools or



2x 72 tii

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