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Surging and popping?
I have been adjusting the timing, dwell and carbs. Got it running better but the motor is surging between 1000-1400 RPM and the #4 carb is popping or backfiring. Any ideas?
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1974 911s "It smelled like German heaven" http://www.youtube.com/watch?v=6ySt9SeZl9s |
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12-10-2007, 05:26 AM
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Join Date: Dec 1999
Location: Novato, CA
Posts: 4,740
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I would put the CIS back on.
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12-10-2007, 06:32 AM
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2.2l with Zenith carbs.
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1974 911s "It smelled like German heaven" http://www.youtube.com/watch?v=6ySt9SeZl9s |
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12-10-2007, 11:14 AM
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Location: Novato, CA
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Figures.
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12-10-2007, 11:46 AM
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Anyone???
Standing frozen in garage with tools in hand. Sound of crickets churping in the background....
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1974 911s "It smelled like German heaven" http://www.youtube.com/watch?v=6ySt9SeZl9s |
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12-11-2007, 02:40 PM
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I will start by saying that I am not an expert.Try pulling out your idle jets and blowing them clean.I don't have a compressor but I use a can of the air you buy for cleaning computer parts ect.I make this part of my regular maintenance.
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Brent Lineker 1975 911S weber conversion. |
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12-11-2007, 02:55 PM
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Location: louisville
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Have the carbs been rebuilt at least cleaned and new gasket kit's would help if they havent
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Tony Proasi 1969S 1957 VW Pickup |
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12-11-2007, 03:19 PM
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+1 on the idle jet's. I would have to clean them out almost every thousand miles on my old Weber'd 2.7. It would get so bad that it felt like it was running on 3 cylinder's. Remove the idle jet's, blow them out with air & pop them back in. Should run OK after that!
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'85 Carrera Coupe, Marble Grey #118 JP/R6 '93 Lexus SC400, '00 Ford F-150 '70 911T- 2.7 (SOLD) |
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12-11-2007, 03:51 PM
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The carbs were rebuilt fairly recently but I will give it a try.
THANKS
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1974 911s "It smelled like German heaven" http://www.youtube.com/watch?v=6ySt9SeZl9s |
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12-11-2007, 04:55 PM
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I have a 2.2T with Zeniths. 54,000 documented miles, one registered careful owner before me. Neither the engine nor carbs have ever been rebuilt.
I had the same problem as you described, even though everything was to spec (carb sync, good throttle shafts, timing, plugs, replaced spark plug wires, valves, points, cleaned the carb jets and passages, etc.). Everyone said, "that's just Zeniths", but I refused to believe it. It pulled strong, but was not as smooth at part throttle and would pop from time to time. After going through the car top to bottom, and searching a bunch on this board, I read several posts where they recommend that Zenith idle jets should be bumped up one or two sizes. You'll have to search this Forum, but I think stock is 45 and they recommended 55 (or something like that - I did it one year ago). Apparently, Zeniths need a bit more fuel from idle to transitioning to the mains with our modern crappy, oxygenated, ethanol fuel. So, I bought the jets from my favorite VW supplier, as they just happen to be the stock-sized idle jet for Solex 34 Pict-3 carbs on 1600 CC dual port aircooled VWs ('71-on). Being VW, they were also cheap. The difference was night and day! From thinking that my carbs needed rebuilding to a smoooooth ride. A few bucks, a few minutes to install, and life is good. My 1.5 cents. Good luck. John Last edited by John P (w/a T); 12-12-2007 at 08:32 AM.. |
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12-12-2007, 08:29 AM
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John, I am on it.
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1974 911s "It smelled like German heaven" http://www.youtube.com/watch?v=6ySt9SeZl9s |
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12-13-2007, 06:52 PM
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1974 Porsche 911s
