2000 Ford Focus Loss of Power

Tiny
MAZCRAZ
  • MEMBER
  • 2000 FORD FOCUS
  • AUTOMATIC
My 2000 ford focus is losing power on hills and shakes a lot. I have already replaced the air flow sensor and the air intake valve, and I plan on possibly replacing the O2 sensor and I'm replacing the spark plugs. What could be contributing to the power loss?
Saturday, June 13th, 2015 AT 4:26 PM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,873 POSTS
Shaking is due to a misfire, so that's what you need to address. Don't just throw random parts at a problem. That is the most expensive and least effective way to diagnose something. The mass air flow sensor measures the weight of the air coming so the Engine Computer can calculate how much fuel is needed to go with it. The oxygen sensors just tell the computer the results of what has already taken place in the engine. Changing the messenger doesn't change the message. Neither of those sensor will cause a misfire.

The spark plugs ARE the logical suspects, but there are other possibilities. You didn't bother to list the engine size or mileage. We need to know the mileage to make judgements on some other suspects that might be popping up. When you have an engine or engine-running problem, we need to know which engine you have. In this case, if you have individual ignition coils, one for each spark plug, and new spark plugs don't solve the misfire, you can swap the coils between cylinders to see if the misfire switches to that other cylinder. (Your car should have the Check Engine light on, and a diagnostic fault code indicating which cylinder is misfiring now). If your engine uses a coil pack with multiple coils in one assembly, you'll have spark plug wires which are another good suspect. Those should be replaced anyway based on mileage.
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Saturday, June 13th, 2015 AT 5:56 PM

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