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Why Is My Engine Losing Power Under Load But When I Turn It Off Then On… It Works Fine.

Posted in Engine & DriveTrain | Asked on Sep 23, 2011

I have a 1993 Ford Mustang that I am hoping to restore. However it has recently started running poorly.

When I first start it… it takes a while to warm up before it will run properly. Then it runs fine until I put it under load (Such as on the freeway uphill). Then it loses power. And the thing is… I can actually feel the exact second that it loses power. Almost feels like it is losing a cylinder or 2. After this happens… when I try to give it more gas… it sounds like the engine is knocking. This problem continues until I stop the engine. However, if I stop, turn off the engine, then turn it back on… the problem is fixed. Every time. Until I put it under load again, of course.

I have recently changed the fuel filter, air filter, spark plugs, spark plug cables, distributor cap, rotor… so those can pretty much be ruled out.

Im pretty stumped. Any help would be greatly appreciated.

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There are 4 Answers for "Why Is My Engine Losing Power Under Load But When I Turn It Off Then On… It Works Fine."

  1. Ironball says:

    Sounds like a plugged catalytic converter

  2. Clayton M says:

    Miles on car
    80,000 miles fuel pump going out 1/4 tank of fuel keeps it cool may last longer – 160,000 same oh deal 1993 get it

  3. Grant says:

    Check the vacuum lines if you have a vacuum leak your engine will act like your losing power and it will hesitate when you hit the gas

  4. Iwannaknow says:

    Could be a timing problem could be a vacuum problem could be a catylitic converter problem could be a fuel pump about to go out …could be a sensor problem for instance it might be the maf sensor it could be dusty and not giving you an acurate reading and when you put your car under a load it is not putting the right amount of fuel into the cylinder therefore you might flood the cylinder causing it to miss out …..when you stop the car it resets the computer and starts over again…..i would take it somewhere and get a shop to hook it up to a graphing modis computer and take it for a test drive to see exsaclty what it is doing ….might pop up a code and you know right where the problem is…..