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Proper vacuum (stock '02) (archive)
[ Follow Ups ] [ 2002 Message Board ] [ Msg. Board FAQ ]
Posted by John Weese on June 25, 2000 at 12:59:39:

Ok, I'm getting real tired screwing around chasing this "missfire" I've been having...engine starts and runs fine, except for an intermittent missfire (very faint...but not right...especially "at speed")!

Bought a vacuum gauge and did the following:

disconnected the vac line from the dist(stock) to the intake manifold and put the vacuum gauge on the intake line (left the dist open)....the vacuum gauge read around 10 (in Hg) at idle...with throttle, the needle bounced to zero.

then, I put in a "tee" in the vac line between the dist and the intake manifold (and removed the vac line to the charcoal canister)...so I had a "tight" system...the vacuum gauge reading was about 18 to 20 in. Hg at idle...upon throttle the gauge dropped to around 5 in. Hg.

This tells me a couple of things: I should most likely only test the vacuum on a "closed" system...when the charcoal canister is attached to the intake manifold it can't be closed....and the dist. is left "open" when the line is removed.

The vacuum reading of 18 to 20 inches is "normal" for the reading on a "closed" system...this is a good thing..right? Anyone know what BMW spec is?

Should I just disconnect the line to the charcoal canister?...then the "only" vacuum line would be from the distributor to the intake manifold (right beneath the 32/36 Weber)...btw, the suction line on the base of the Weber is "plugged".

Or maybe I should just replace the distributor with a mechanical advance one and the "only" vacuum line would be to the Charcoal canister (not counting the brake booster line of course).

Any thoughts? As you can tell, this '76 2002 has all the pollution control "crap" removed! Very clean in there !

TIA for any suggestions...I'm getting there...slowly but surely...

John
'73tii - In the Garage too much :(
'76 '02 - Daily Driver...still missing!
'74 '02 Parts


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