1994 Mazda B4000 Misses Under Load

MAZDA TRUCK
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MEANGENE256
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I have a 94 Mazda B4000 with 304,000 miles on it and it ran fine until a few months ago. Now it idles a little rough, but mostly misses when it is under a load, like driving in too high of a gear, and when I run my a/c. I just replaced the plugs a couple months ago,,any ideas, besides the high mileage?
Apr 15, 2006 at 7:36 AM
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LOSONE
  • ✓Experienced Mechanic
  • 1,616 POSTS
That is a Ford 4l engine and the coil packs are a prime suspect. They are a medium failure rate. Good luck
Apr 15, 2006 at 10:48 AM
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FIXITMR
  • ✓Experienced Mechanic
  • 9,989 POSTS
i agree it could be other items in spark path. or mixture is leaning out.
Nov 14, 2011 at 10:49 AM
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Suggested Repair

Inspect the coil packs first, since they are a common failure on the Ford 4.0L engine used in this truck. Also check the rest of the spark path and look for a lean mixture under load.

Conversation Summary

A 1994 Mazda B4000 with 304,000 miles idles slightly rough and misses under load, such as in too high a gear, and when the A/C is on. The plugs were recently replaced. Experts say the Ford 4.0L coil packs are a prime suspect and that other spark-path parts or a leaning mixture could also cause the miss.

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