1993 Mercury Villager no power on acceleration

KORPONAY

MEMBER
1993 MERCURY VILLAGER
6 CYL
FWD
AUTOMATIC
204,000 MILES

It starts and idles great. On acceleration it acts like it is starving for fuel sometimes back firing in the intake.
Fuel pressure and pump delivery checks out good. New cap, rotor, plugs, wires. It's set a code 33 OX sensor cicuit and 34 knock sensor circuit. Installed OX sensor, no difference, Knock sensor hard to get to. Any other suggestion. Checked timing it is advancing as it supposed to. If you pump the pedal as you start to accel it will wind up with power than flatten out unless you back off the pedal. Sometimes it will have power intermittenly. Thanks John

7 Replies

MMPRINCE4000

MECHANIC
8,549 POSTS

Perform or have performed a backpressure test on the convertor. If clogged or partially clogged, it will cause the symptoms you describe.

A lean or rich mixture can cause the convertor to overheat. The car will idle OK but when under load, the exhaust gases will back up causeing loss of power and backfiring.

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Sunday, March 22nd, 2009 AT 9:21 AM

KORPONAY

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3 POSTS

Thanks, I didn't mention that even if I try to rev the engine off of idle it will act like it is not firing on all cylinders. I pulled off the plug wires when it is doing that and sure enough there was spark but a couple of the cylinders were were not having power. When driving some times it will pick up and run on all cylinders. Hope that helps a little. Thanks, John

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Tuesday, March 24th, 2009 AT 3:06 PM

MMPRINCE4000

MECHANIC
8,549 POSTS

While it could be a lot of things, I would check convertor first.
Loss of power is usually associated with convertor, but could also be low fuelpressure, or ignition.

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Wednesday, March 25th, 2009 AT 6:43 AM

KORPONAY

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3 POSTS

Converter is good. Fuel pressure is good to. Checked spark at plugs and they are firing strong when I rev it. It acts like some of the injectors are not working but it idles very smooth and it does rev up sometimes, than it goes into the missing mode. It acts like some of the cylinders are not running. Any other ideas. Thanks, John

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Sunday, April 5th, 2009 AT 1:09 AM

MMPRINCE4000

MECHANIC
8,549 POSTS

Have ignition module tested, if fuel pressure and CAT are good, I would concentrate on the ignition. Module would be first, but also check cap for cracks, rotor, wires.