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> Jensen Healey & Jensen GT Tech > Engine & Transmission > misfire under load at 4600 rpm or so

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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?

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.

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

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.

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.

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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