engine bucking or********

2004 MERCURY MOUNTAINEER
97,000 MILES • V8 • AWD • AUTOMATIC
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BRACEB
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No repairs have ever been made to this vehicle to my knowlege.it has 97,000 on 40,000 of which I have put on it.I recently changed the oil.about 100 miles ago.today while driving my engine started bucking when I hit 50mph stopped when I slowed,but started again when I picked up speed.I was on the highway and was about 5 miles from so continued driving then an engine override light came on.What is happening.It runs and Idles(has a slight surge when Idling)
Jan 12, 2011 at 1:35 AM
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LEGITIMATE007
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scan the engine for codes and bring back to me
Jan 12, 2011 at 7:24 PM
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BRACEB
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I had the vehicle scanned at auto zone.No codes came up.I filled my tank put in a can of heet seem to run fine.Gotgas mileage has gone down from 18 to 12 mpg.it stalled out once at a stop light.It did start again.I was able to get home.The engine surges slightly at idle about 50 rpm when idling.Could my fuel pump be going?
Jan 16, 2011 at 5:04 AM
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LEGITIMATE007
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it could be, but you need to check fuel pressure, and I would also check the iac. and clean out the throttle body, I think the iac may be eratically, and one more thing, the mass airflow sensor, may be faulty or just need cleaning.(there is a special spray for that.
Jan 16, 2011 at 3:00 PM