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Loss of Power

New to posting on here. I have encountered a problem and haven't been able to diagnose the problem or successfully find a thread that addresses what I am experiencing.

I have a 74 911T with a rebuilt 2.7L that was converted to carbs mated to a rebuilt 915. I was on the highway cruising at about 65mph when I noticed that I was having to apply more and more throttle to keep the car at the same speed until my foot was eventually planted to the floor. No noticeable change occurred with the sound of the engine.

I pulled to the side, shut the car off immediately to try and figure out what had happened. Since I was in a bad place on an off-ramp I decided to restart the car and get off at the next exit. Car started, seemed to run okay except that the power felt weak, for lack of a better word. Any thoughts on what I would check first?
Old 04-18-2014, 10:14 PM
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How does it response if push down the throttle for a second? ( not driving )
If you drive normal, so not accelerating, do you also feel power loss?
Old 04-19-2014, 12:19 AM
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Maybe brakes jamming on?
Old 04-19-2014, 05:31 AM
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If the condition persists I would suspect a clogged catalytic converter. That would be a perfect excuse to get a cat bypass.
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Old 04-19-2014, 06:05 AM
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blnee,
Have you tried posting in the 911 Technical Forum? None of us in this Turbocharging Forum have carbs.

Did you notice if the temperature gauge was rising with this occurrence? It sounds like a air/fuel delivery problem as long as the oil temperature is not an issue.
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Old 04-19-2014, 06:25 AM
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Quote:
Originally Posted by Dr J View Post
If the condition persists I would suspect a clogged catalytic converter. That would be a perfect excuse to get a cat bypass.
Were there CAT's on '74s?

Might just be a weak ignition problem, sparking but weakly. Coil, maybe?? Or, plugged up air filter (mouse living in there?).
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Old 04-19-2014, 08:06 AM
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I've had lots of experience with rebuilding and rejetting multiple Weber, DellOrto, and Solex carbs on 4 cylinder BMW 2002's and 4 cylinder 912 Porsche's I used to have.
If this all happened in a short period of time it sounds like fuel starvation as in a fuel pump stopped working (may just be a dirty fuse connection) and then the fuel level in the carburator float bowls went down and the motor gradually loses power as it did.
Old 04-19-2014, 08:19 AM
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Good point Mark. I did a little checking and it seems cats came aboard in 1978.

One less thing for the OP to check!
Old 04-19-2014, 09:56 AM
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Quote:
Originally Posted by WERK I View Post
blnee,
Have you tried posting in the 911 Technical Forum? None of us in this Turbocharging Forum have carbs.

Did you notice if the temperature gauge was rising with this occurrence? It sounds like a air/fuel delivery problem as long as the oil temperature is not an issue.
My passenger seems to remember the car getting hot but I don't recall that at all. My oil pressure gauge is inconsistent at best but I almost always keep an eye on the temperature gauge and I don't remember it being abnormal.

I posted over on the Technical Forum too. For some reason I didn't notice I dropped this in the Turbo section but I appreciate the suggestions so far. I will check the fuel pump and fuse and start there.

I haven't started it since this happened. My concern was that if it is oil pressure related I could damage something. Not sure if that is legitimate or not.
Old 04-19-2014, 10:12 PM
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i would check fuel filter and fuel pump first.
if you have one of those small i am guessing clear fuel filters, they can clogg pretty fast.
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Old 04-21-2014, 03:23 AM
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All those guessing fuel filter win the office pool. Both inline filters (the little small ones) looked clear but upon taking them off dumped a bunch of sediment. Car started right up after replacing them.

Thanks for saving me a bunch of time and head scratching.
Old 04-30-2014, 08:38 PM
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