Help diagnosing Engine issue

Wobdog

Wobdog

a.k.a Mike
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Need the forum help here, keeping in mind I do not know allot about engines. Here are the symptoms

  • Car starts right up no issues, and idles smooth
  • After car is warmed up sitting at a signal for more than a minute the RPM dropa from around 1000-950 (smooth idle) to 500 and seems like it swill stall out, although it never does.
  • Once this symptom happens giving is gas or flooring out has a very delayed reaction and then revs
  • When stopped at a signal, revving it does bring the car back to a normal ideal
Other information, I had spark plugs, air filters and a tune up one year ago



On a related note, can anyone recommend a good E9 manual so I can learn more? Chiton?
 
Hi Need some more info original zenith carbs or webers, if so, which ones? Or is it fuel injected? Original engine? Auto or Std? Has the car been sitting for quite awhile? Sorry for all the questions but more info, easier to help you

Thanks, Rick
 
Did this just happen or has it always done it?

Who did the "tune up" and what did it include besides spark plugs and air filters?
 
Sorry- More info. Original 1971 2800CS Zenith carbs. It just started to do this. My local BMW mechanic did the tune up last year when I bought the car.
 
Air or vacuum leak. Is retard line from dizzy to front carb attached? When actuating linkage do both arms move at exact same moment?
 
Wobdog said:
On a related note, can anyone recommend a good E9 manual so I can learn more? Chiton?
Click to expand...
There's a manual available on the forum along with a host of other info. Click on "Home" above and then "Technical Resources" or "E9 Tech Info." Poke around once you're there and you should find quite a few helpful resources.

Here's the location of the manual:

 
Had my mechanic look at it when he installed a new clutch master and slave cylinder and he said he just adjusted the dwell. Runs fine again
 
If you still use a mechanical FP driven off the cam, you may have a weak fuel pump that causes a low float level at idle. Raising rpm up increases flow enough to bring float level back up.

How long is it between
(1) idle rpm drops and then you rev it up to get idle back to normal (start timer)
(2) idle rpm drops again (stop timer)
 
Points can be a PITA, but their one redeeming value is a graceful failure mode combined with ease of road-side repair. Pertronix, in contrast fails catastrophically. Friends who use Pertronix still carry a spare.
 
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