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Rough idle 1976 2002

Guest Anonymous

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Guest Anonymous

I have a 76 2002 daily driver with a Weber conversion that spontaneously developed a rough idle. I drove it on Friday and it ran great, but when I went to start it this morning, the rough idle was there.

I pumped the gas pedal 2-3 times as usual and spun the engine over and the first thing I heard was a pop from under the hood, followed by a little bit of smoke. I opened the hood, but couldn't find anything obviously wrong, so I tried starting the car again. After several attempts to start it, I finally got it running, but the the car won't run unless it's under ~1/2 throttle and even then, it's sputtering badly with no power whatsoever.

I pulled 2 of the spark plugs and they were rather black and smelled strongly of gas. The boot of of the 2nd plug wire front the right came apart as I took it off, so perhaps it's time to replace them all. I can't tell if there's too much fuel, or not enough spark, but the car was running perfectly on Friday.

Any ideas? I'm going to replace the defective wire and check the other 2 plugs, but beyond that, I'm stumped.


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You have some diagnostic work in front of you!

Rather than throwing parts at it, try to get yourself back to a baseline- check all the ignition components, test the ignition coil, reset the points, etc. I assume the car won't run well enough to set the timing.

Your symptoms reek somewhat of a bad condenser (especially the inability to run under load), but you need to check everything off the list first.


'73 2002 Warmbold Rally Car Imitator

'89 325i Time Capsule

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The first thing I would check would be the "Idle cut off solenoid". There is a single wire that clips to a small cylindrical part on the passenger side of the carb near the front, down low. It is the only wired part down there. Are all you gauges working? The solenoid is on the same fuse that all your gauges are on. If it is disconnected, the car runs really crappy or not at all. It may have become disconnected, the wire may have broken, the connection sometimes breaks. or, the fuse blows. Fuse #12


Hope it is that simple of a fix...

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1974 Inka 1802 Touring, New Daily Driver

1976 Inka 2002 Original Owner (adopted by Scott B.)

My Roundies are bigger than yours

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The suddenness of the problem points to ignition system.

One quick check is if your tach needle bounces around and/or zeros out while the engine is still revolving, it is ignition.

As long as your points are in tact, I would start with the condensor and then the coil.

67 Caribe 1600

76 Ceylon 2002

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hi, i had a similar issue on my '69. heard a pop, or backfire, then car would not idle. of course i thought the worst. but what happened was my vacuum plug(s) on my manifold 'blew' off for some reason, i replaced them, made sure they were tight and never had it happen again.


1969 Colorado Automatic (converted to 4spd)

1982 528e
1972 BMW R75/5


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  • 7 years later...

I had the same problem with my 1976 BMW 2002. I have a Weber 32/36 carburetor with a water choke. It is also equipped with an idle solenoid. The care started with a rough idle, then after doing a major tune-up, the problem still existed. Then after checking the entire ignition system, I finally found the problem with the idle solenoid.

    To check the problem, make sure you are getting 12 volts to the solenoid. This was done by disconnection the wire to the solenoid and attaching the wire to a volt meter, and then turning starter key, not trying to turn over the engine, just applying 12 volts to solenoid.

I was getting the around value of 12 volts  as expected. I Then remove the solenoid and pull out the idle jet - this exposes the needle, that is plugs into the idle jet. Then connect the +12 volts lead that was connected to the solenoid, and then ground the solenoid body. Apply 12 volts to the solenoid, by turning the starter key, but not turning over the engine. the center needle should retract. If not, then the solenoid is not working as it should. I happen to have an extra idle solenoid, was not sure if it worked or not. I applied the same test to this solenoid. The needle retracted as expected. reassemble the new solenoid with idle jet and placed it back into the Weber. Then the problem was solved. Hope this helps. In the future, I will keep an extra solenoid on hand - the problem has happened before - I just forgotten the solution.


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