Motor bucking when under a load

  • 2000 FORD FOCUS
  • 255,000 MILES
Ok. I read thru alot of the questions but there are alot.
anyway. We have a 2000 focus ZX3. It has been a great car. Save for normal maintenance. The past 10,000 miles or so it has had this weird bucking, like it is running out of gas. We thought it was the fuel pump going out. Its old, etc. We changed it. And new fuel filter at same time.
it made it for a full day with out doing it again. I asked my dad (mechanic, owns own business) about it. He had us come down and run diagnostics on it. The light wasn't on at the time we changed the fuel pump. Now it is. It was coding P0172. So we changed the O2 sensor. Got better for a few hours but started again. While changing th O2 I noticed a vac line on the back off the throttle body had collapsed, so I changed it as well.
happens mostly when it is warm outside and engine is up to temp.
then it coded for a misfire on 4 so we changed out plugs and wires. Then changed out the MAS.
Each thing we do to it makes the problem lessen. But it was still doing it saturday when we put the MAS in. But now it is coding P0172, P0442 and P0113. I think we may have done the 442 with the evap lines on the fuel tank but gonna try gas cap first. And it came up way after the bucking. I plan on changing out the IAT, but am at my wits end on trying to figure this out. Is there any advise you can give to this problem.
Do you
have the same problem?
Monday, October 8th, 2012 AT 7:14 PM

1 Reply

P0113 - IAT. Ensure the temperature sensor wirings are good and plugged in correctly.

P0172 - System too rich. Can be triggerred by the IAT fault.

P0442 - EVAP system small leak detected, could be the loose fuel cap you mentioned.
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Monday, October 8th, 2012 AT 8:09 PM

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