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Daily driver down....
My 74 2.7 started running rough on the way back up the mountain yesterday. Rough like not on all cylinders, not rough like electrical, and it wasn't intermitent...steady rough. And it was obviuosly down on power, but no smoke like failed rings and no real noticable change in tone like metal on metal. I will pull the plugs this morning and do a quick and dirty compression check. Fuel pump up front has been noisy of late, but fuel pumps usually work or not, and when I have had fuel pump issues before the car stopped running. CDI problems are electrical in nature and work cause sporatic firing ...yes? This felt like the engine was running on 4 cylinders with 3 of them on one side. The idle was fine...not as smooth as normal, and it doesn't hesitate, cough or try to die. Seems happy to run, just down on power.
Answers to your questions in advance... 1) I have no idea of mileage...high say 150-200k 2) yes it does leak...not terribly, but always has 3) I run it a bit rich w/ AFR at 13.5 4) stock CIS for a 74 2.7 no mods 5) Original CDI and electronics Any suggestions you guys might have would be appreciated. This has always been the little engine that could. I know it was going to deserve a rebuild at some point, and I might have accelerated that time line by four of us flogging it at the PCA autocross two weekends ago...for 24 runs. Seemed to be happy afterwards and drove home just fine. We have had two 1 ft snow storms recently and he was unfortunately outside during the last one and got thouroughly covered with snow. I can't see how snow/water melting through the decklid into the engine compartment could have caused an issue. Anyway...open to suggestions. Speedo |
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11-06-2011, 06:21 AM
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Any difference after spending a night in a warm/dry garage?
Moisture in the ignition system will sometime present as above, but if you've been driving her after she got wet I'd think that the engine heat would have dried everything out by now. |
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11-06-2011, 06:33 AM
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76 911S Targa
Join Date: Oct 2010
Location: Idaho
Posts: 1,150
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Water in fuel? Run some injector cleaner through it.
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76 911S, 2.7, Bursch Thermal Reactor Replacements, Smog Pump Removed, Magnecors, Silicone Valve Cover Gaskets, 11 Blade Fan, Carrera Oil Cooler, Turbo Tie Rods. |
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11-06-2011, 06:45 AM
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Registered
Join Date: May 2004
Location: Lake Cle Elum - Eastern WA.
Posts: 8,417
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My 73.5 started running rough all of a sudden. Was a dirty injector. Determined which one by checking the flow pattern, cleaned it myself and was back in tall cotton.
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Bob S. 73.5 911T 1969 911T Coo' pay (one owner) 1960 Mercedes 190SL 1962 XKE Roadster (sold) - 13 motorcycles |
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11-06-2011, 06:58 AM
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Free minder
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When was the last time she had a tune up? If it is overdue, I would start there: new cap, rotors, spark plugs, check advance.
If problems persist, I would pull th injectors and check flow on them. You may find some are not flowing as much as others. If that is the case, you can try to clean them in ultrasonic bath ( I did dichloromethane then isopropanol). If still problems, maybe look for an air leak in the CIS...
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1978 SC Targa, DC15 cams, 9.3:1 cr, backdated heat, sport exhaust https://1978sctarga.car.blog/ 2014 Cayenne platinum edition 2008 Benz C300 (wife’s) 2010 Honda Civic LX (daughter’s) |
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11-06-2011, 07:00 AM
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ruff
So fuel issues, injectors, water in fuel. My experience is the engine would "buck". This isn't gasping...just feels like it is out of balance. One of my inlectors number 5 is leaky around the base...just moist. I should probably pull the injectors and test the pattern. Can I just do that with the ignition "keyed" and the fuel pump running (engine not running) spraying into into a jar?
Speedo |
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11-06-2011, 07:50 AM
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Registered
Join Date: May 2004
Location: Lake Cle Elum - Eastern WA.
Posts: 8,417
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Quote:
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Bob S. 73.5 911T 1969 911T Coo' pay (one owner) 1960 Mercedes 190SL 1962 XKE Roadster (sold) - 13 motorcycles |
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11-06-2011, 08:18 AM
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ruff
"push the plate up"...you mean take the airbox/cleaner off and reach inside to access the "plate"? Or simply engage the throttle?
Speedo |
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11-06-2011, 08:31 AM
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Quote:
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2021 Model Y 2005 Cayenne Turbo 2012 Panamera 4S 1980 911 SC 1999 996 Cab |
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11-06-2011, 08:45 AM
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Registered
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It was cold here today...
Wind was blowing 25mph and then temp was below freezing. I managed to pull all the plugs and check connectors. Plugs looked normal. I was worried about an unusual plug...dirty, oily ie hole in piston or broken rings. Nope, they all looked the same. I cleaned and regapped all the plugs and reinstalled. It was too cold outside to do much else. Fired the car up and it seemed to run fine. Will see tomorrow.
Speedo |
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11-06-2011, 06:11 PM
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1974 Porsche 911 2.7
1985.5 Porsche 944 2.5L Supercharged 
911 SC
Panamera
