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Thread: 99 B4000 4X4 Rough idle, hesitation at different speeds.

  1. #1
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    99 B4000 4X4 Rough idle, hesitation at different speeds.

    Hello all, and thank you for any assistance you may have.

    I have a 99 Mazda B4000 4X4 with 103500 miles on it. I recently had a check engine light come on ( a week ago) an the code was, #1 Oxygen sensor. At the same time, the hesitation while driving and at idle started. I was doing about 65 mph when this all started.

    I replaced the Oxygen sensor, and reset the check engine light, by removing the battery cables.

    The problem still persists, so after a little research, I cleaned the "Mass Air Flow sensor". That drastically improved performance. For about two days, than it returned to the poor performance.

    I have now replaced the ""Mass Air Flow sensor". On first staring the truck, idle ran rough, and had some hesitation. Drove a few miles, an "Wow" problem fixed....

    Sadly problem returned, prior to making it back home.

    So we have;

    Rough idle (stars fine, runs fine, gets rough, then ok, then rough again)

    Hesitation or jerky when driving at different speeds (all most vibrates you out of the seat at times)

    If I stomp on it, it gets worse, let off an it is fine for a bit. then starts again.

    No Check Engine light.

  2. #2
    Senior Member MrMarty51's Avatar
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    Might have to take it to a auto parts store, auto zone, oriellys, and have them hook it to a code reader to clear the codes completely from the memory, then, it`ll take some driving for the ECM to relearn what it is suppose to be doing.
    Might even be a driving procedure that needs to be followed to get the parameters properly set.
    If You do`nt have a service/repair manual, I`d suggest to get one, procedure for relearn should be in there.

  3. #3
    Senior Moderator chevychase's Avatar
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    I would check for vacuum leaks can get carburetor cleaner spray at base of throttle body and vac lines if it idles high while spraying you found vac leak.
    Also like marty said run truck some see if you get another code. Also might do a good tune up on it plugs ect. Check fuel pressure.
    Maybe change the fuel filter. What was the code po..? Could be many things cause this..be nice if code would set.
    Also if you do a search on your problems ..search ford ranger with your engine size and year get better results..same as your setup.

    Gitter done have fun. Running on empty...running blind...running behind.....

  4. #4
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    I had the Auto parts store clear codes as recommended by MrMarty51,then went for a drive and took wife to store. When we got back in the truck, the "Engine light " came on. So back to the parts store we went!!!!! New code, misfire on #4.

    Replaced plug, problem seems to be solved.

    Special note, this is the 3rd time in two years that I have replaced the same plug....

    Thanks again for all your help..

  5. #5
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    As suggested, I went to the auto parts store and had them erase the computer. There were no codes to read. After a short drive and shopping trip with the wife, when I started the truck I got a check engine light.
    Turned out to be a misfire on #4. I replaced the plug, and problem solved.

    Special note, I've replaced the same plug three times in the last two years.

  6. #6
    Senior Moderator chevychase's Avatar
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    Did the plug look black sooty? Maybe getting fouled with oil . Thanks for posting back ..glad you got it running right .
    Oh if plug getting fouled with oil can get a non foul adapter screws in plug hole keeps the plug away from the oil lasts longer ..till you can get it fixed.

    Gitter done have fun. Running on empty...running blind...running behind.....

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