Question about 1999 Mercury Tracer

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1999 tracer with an engine idle that increases and then decreases while stopped.While driving, the engine will buck in any gear.The pcv valve and the fuel filter were replaced.Tests were done on the fuel pressure and fuel injection systems.they were good.plug wires and plugs were replaced.The idle control valve was replaced also.This problem seams to begine after a few miles of driving the car.

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Other than the idle control/throttle sensor the other items will not usually cause bucking or change of idle. After you drive awhile from a cold start the coolant temp sensor comes into play,then the EGR valve if vacuum is involved under load. So I quess your mechanic missed monitoring the 02 sensors after testing the fuel system. Hard to imagine. Have to road test hot for Egr and other drivability issues. You need a good drivability tech and always stick with best in their field. Hard to find. Have you ever gone for a drive with the person going to work on your car sitting in the pass seat. If they don't insist on that before they ever look at your veh or take your money--enough said. Did they call you to see if your happy with their performance? If not move on. MAF,AIT, most likely on idle and EGR on bucking. Quick look at 02 sensors You or they did a good job,Just didn't hit a home run,still on second base.

Posted on Sep 29, 2009

Testimonial: "i am not sure what the "MAF or AIT" are or what they do.I will replace the EGR valve.Thanks.."

  • Anonymous Sep 30, 2009

    Hold on. I did not tell you to replace anything. You have to test to confirm an issue, not throw parts at it. Read what I said. You have to road test, hot---when you TEST an EGR VALVE. Disconnect any vacuum hoses on the EGR and plug,then road test. You want it out of the system. This is a step by step process one item at a time. I told you an EGR may cause bucking. Next. When that problem is gone we proceed to the IDLE ISSUES. There you will need a scan tool you won't have , to check Mass Air Flow Sensor (MAF)(AIT) Air Intake Temp,may be in one senor. PEASE READ EVERYTHING I WROTE and seriously consider getting this done professionally.



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