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misfire under load at 4600 rpm or so  Rate Topic 
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 Posted: 01-26-2011 03:34 pm
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andrewo
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I have been driving the car more lately, and have noticed that up around 4600 rpm under load in 3rd gear, I just lose power. It almost feels like the engine isn't getting fuel, or isn't firing. No problem in lower gears, or out of gear, but when headed up a hill, or an on-ramp. it is stumbling. The only way around is to up shift or let off the gas. It seems like it might be a carb problem, but I still running points, so could be ignition. Or even a vacuum leak.

Any thoughts?

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 Posted: 01-26-2011 03:37 pm
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JodyKerr
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Step 1 - Fuel delivery, make sure you've got a clean fuel filter

Step 2 - Timing - make sure it's on, points clean, etc.

Step 3 - Carb - check for lean condition.

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 Posted: 01-26-2011 04:31 pm
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Jensen Healey
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Hi Andrew,

You can run to redline under load in 2nd gear but not 3rd? That doesnt seem possible. Please test again.

Power loss at higher RPM is usually a fuel delivery issue. Which gear you are in shouldn't matter though. 

I would guess either the fuel pump isn't doing it's job or the filters are clogged. 

Kurt

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 Posted: 01-27-2011 12:58 am
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CarlosThe Jacker
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Are you possibly hearing a crinkling noise when the power loss occurs, faint like someone making and aluminum foil ball under the hood? If you downshift, does it get better? You said upshift, what happens if you jump to fourth? Do these trans have bearings that could be going and only affecting 3rd?

Otherwise agree with previous answers, also wires, points, anything in the secondary could be it.

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 Posted: 01-31-2011 11:16 pm
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Dan Collier
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Check the ground wire inside the distributor. I once had a problem of intermittent running. Plagued for months. I replaced the points and condensers a couple times before finding the braided ground strap had broken wires inside.

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 Posted: 02-16-2011 09:45 pm
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andrewo
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Turned out to be fuel delivery after all, but the pump is fine. Just a lot of crud getting sucked into the lines and the filter. It definitely was worse under load and in high gears, which I agree is strange, but I swear true. I had no problem getting to 6 grand in 2nd.

Running fine now. Thanks for the responses.

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