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YouTube video of some odd idling behavior today..


stevebo77

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Never had this issue until yesterdays inaugural run down to town for registration and new tires. Ran fine all day, but started behaving very poorly by the time I got back home (2000 ft climb, 9 miles from ocean).. could barely make it up my last stretch of hill before stalling on my street and now stuck with the behavior shown in the video above.

Last night I pulled the 32/36 off and did a full cleaning, bath, reassembly, set the baseline Redline idle mixture and speed to their prescribed settings. It runs fabulously until after WOT.. then struggles between 200 and 1000 RPM.

If any of the behavior in the video looks familiar, please chuck some pointers my way :)

hryniukBMW.gifSteve Hryniuk

Hilo Hawaii

1973 BMW 2002

Project Honu Blog

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Might have something to do with the fuel or air feed for the idle circuit. For example, if the needle valve is a bit sticky, when you blip the throttle it might be sticking open a bit, causing a tiny bit of flooding at idle. You could try knocking the body of the carb near the bowl with the end of a screwdriver a few times to see if things settle down.

It is possible for air to leak past the idle mixture adjustment screw, with the throttle blipping causing vibration in the carb and the screw to reseat a tiny bit allowing air into the idle circuit and excessive leanness to occur. I realize the second theory is a stretch, but it happens frequently with older DCOEs, and is easy to eliminate as a possibility. Just put a bit of vaseline on the screw threads and retest.

This problem would be vastly easier to diagnose if you had an air-fuel ratio meter to see what is happening with the mixture. Another diagnostic approach would be to let it idle poorly for a while, shut it down and have a look at the plugs.

Chris B.

'73 ex-Malaga

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So, CD- it would probably help Steve if you would comment on what causes this problem.

hehe Chris_B, well the quotes around the lean idle surge were all I needed to start a whole new night of google searching :)

Sometimes it's all about what to call a problem .. I rarely know how to describe the oddities of this car.

I will definitely check out the possibilities you mentioned of air leaking past the threads. I found today that I can only get it running consistently by turning out the circled screw by the *slightest* amount.. however it seems to rattle loose on its own after a few revs and I have to go back and touch it again.. will order a set of O-rings (hell, I'll order a whole rebuilt kit) to make sure that doesn't rattle out on its own.

I'm not even sure what this screw is, but the sound the carb makes when I touch it implies that it's throwing more air in..

IMG_6244Circled.jpg

After the Youtube video was posted today I started completely over once again with the dizzy timing, then moved on to idle mixture and finally found myself having to adjust the pictured screw. Took her for another (not too aggressive) drive around the hood. Things went pretty well, but I know I don't drive like that in real life. Will have to play again more tomorrow with a partner following behind, just in case.

Oh and @Nepa I saw the video you linked too and double checked my accel pump diaphragm also, very supple and no cracks there, so should be good I guess.

hryniukBMW.gifSteve Hryniuk

Hilo Hawaii

1973 BMW 2002

Project Honu Blog

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Okay. Finally found a diagram indicating that my pictured screw above is the idle jet and screw mount. That helps some..

One last headscratcher that I have is that every photo or diagram of the 32/36 mixture screw pictures a spring loaded screw protruding from the base, while mine is a screw set inside of that hole (deeeeep inside of that hole).. I had to grind down a flat driver today to be able to adjust it.

Abnormal? Who cares? Meh.

hryniukBMW.gifSteve Hryniuk

Hilo Hawaii

1973 BMW 2002

Project Honu Blog

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Double heck!

Now I wonder if my entire project blog is empty? Nahhhh people have commented on the images that are all served from picasa, so I know that works..

Actually if I test that link 10 times in a row, 3 out of 10 return a 404 error and get no image.. google or picasa's servers are being bitches right now I suspect.

hryniukBMW.gifSteve Hryniuk

Hilo Hawaii

1973 BMW 2002

Project Honu Blog

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I am not a 32/36 jock, but I used to run one, and IIRC mine had an idle cutoff solenoid in the spot. That was a device that cut off fuel at idle unless +12V was present at the solenoid. I don't know what goes in there in lieu of the solenoid for carbs not so equipped, but it seems like that might be a spot where air could get in to the idle circuit (or fuel flow could be interrupted) if the screw blocking off the hole was not tight or in the right position. Signing off- kind of late here on the mainland.

Maybe Mr. 32/36 (CD) can shed some light on this when he wakes up this morning.

Chris B.

'73 ex-Malaga

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