engine vibrates 4th/5th gear when driving uphill

1997 MAZDA B2300
110,000 MILES • 4 CYL • 2WD • MANUAL
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LGSASKI
  • MEMBER
  • 1 POST
I have a 1997 Madza B2300 truck shortbed that runs very rough in forth and fifth gear when going up hills. As long as the truck is driven on "level" roads, the car runs fine. It has been in a couple of mechanic shops and I've did/had done some preventive maintenance but the problem continues.
Changed oil to a lighter weight per owner's manual. This did improve the engine's performance.
Changed shark plugs/wires. Problem continued.
Changed timing belt. Problem continued.
Checked Mass Air Flow Sensor/okay. Problem continued.
Ford deslership checked the PCM proportional/okay. Problem continued.
Checked catalyist converter/okay. Problem continued.
Mar 21, 2011 at 10:46 PM
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FIXITMR
  • CAR REPAIR CONTRIBUTOR
  • 9,990 POSTS
sounds like a spark/mixture issue under extreme load. maybe EGR is causing leanness? or coil is shorting under load? does it have a distributor? then cap and rotor or module?
May 27, 2011 at 7:54 PM
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