2003 Mazda B3000 Misfires at high speed

Tiny
HANKER
  • MEMBER
  • 2003 MAZDA B3000
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 133,500 MILES
My truck seems to run fine until about 70 mph when it starts misfiring, causing a sudden jerk. This is particularly evident if the auto speed control is engaged. The truck then continues misfiring and slowing down until about 50 mph then usually begins running o.K. Again. The problem also seems to occur when motor is under stress such as climbing a hill. Can anybody tell me what to start looking for?
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Saturday, January 23rd, 2010 AT 5:21 PM

4 Replies

Tiny
RASMATAZ
  • MEMBER
Check and test all the following below

Oxygen sensor
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)
Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
Cap and Rotor

If it doesn't apply disregard it
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Saturday, January 23rd, 2010 AT 5:42 PM
Tiny
PRW9999
  • MEMBER
The spark advance pickups may be bad in your distributor. These little plastic pieces can sometimes stick and cause your vehicle to stall while climbing a hill. Look under the plastic plate in the bottom of the distributor.
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Monday, February 8th, 2010 AT 3:32 PM
Tiny
HANKER
  • MEMBER
What do you look for? How do you tell if they're sticking? Are they replaceable or do you replace the distributor?
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Monday, February 8th, 2010 AT 9:22 PM
Tiny
BUBLHD
  • MEMBER
I had a similar problem and it ended up being the cam phaser. Unfortunately the rear end seal on the motor had gone out and the engine had gotten low on oil. This caused the bearing to go on the cam phaser and the truck started to misfire and I ended up with engine codes prior to the truck not working at all. I limped it to the dealer (a painful evolution) and a little bit of money later (thanks extended warranty) all was better.
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Thursday, December 23rd, 2010 AT 1:56 AM

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