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Old 10-08-2016, 11:10 AM   #16
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Location: burbank
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Both my 88 and 89 have the stumble at idle. It's like hmmmmmmmmmmmmmmmmmmm--mmmmmmmmm-mmmmmm it's very common but if you find a fix for it please post.

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Old 10-09-2016, 02:45 AM   #17
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Check out this thread. How should an M20 idle anyway?
1990 325i
2004 330i Individual 6-speed


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Old 10-09-2016, 07:08 AM   #18
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Originally Posted by IceWhite View Post
Check out this thread. How should an M20 idle anyway?
Great thread! Nice to know we are not alone with this problem.

There's one other thing I'm goinng to try...there may be an issue with the upper o-ring on my bitch tube. I got a slight idle speed jump when I was dousing my throttle body hose connections with carb cleaner, but only near the bottom. When I replaced the o-rings during the rebuild, I may have gotten a used o-ring in the top position. I think I can R&R the upper o-ring by pushing the tube down (not possible with the lower o-ring). That bitch tube is one of the more irritating design features of the M20, almost as awful as the pushrod tubes on an air cooled VW...
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Old 01-07-2017, 11:45 AM   #19
Join Date: Aug 2016
Location: Los Angeles
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Before you tear into the tight quarters of the bitch tube. You can rule out leaks around the bitch tube, valve cover gasket, oil dipstick by bypassing the hose that runs from valve cover to TB and see if you hear any improvement.

My 93' vert has same issue. Rebuilt motor, changed all sensors, ignition system, seals, which improved things quite a bit and it runs amazingly strong, but still have the intermittent miss during warm idle.
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