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James, Ford Technician
Category: Ford
Satisfied Customers: 3632
Experience:  Ford Senior Master Tech, Ford gas and diesel expert, ASE Certified
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Explorer: 2003 Ford Explorer 4.0 Vin:1FMZU63K83UA13616 vehicle

Customer Question

2003 Ford Explorer 4.0
vehicle runs rough at idle...this is a new motor with approx 42,051 miles on it.
No codes in computer, ran contribution test and 1,2,3 show negative numbers and occasionally they 0 out but mostly -25 and 30
sprayed for vacuum leak and cannot seem to find one.
plugs and wires were changed when new motor installed.
Submitted: 2 years ago.
Category: Ford
Expert:  James replied 2 years ago.
Hello and thanks for choosing just answer. Does the misfire go away when the vehicle is raised off of idle?
Customer: replied 2 years ago.


Expert:  James replied 2 years ago.
If you inspect the crankshaft damper does the rubber insulator feel loose or out of place?
Customer: replied 2 years ago.

he had to leave in it and will be bringing it back in a little while, I will check.

Expert:  James replied 2 years ago.
On this engine the vehicle the damper was known to fall apart. It would feel like a misfire at idle but run smooth off of idle. The balancer would throw the engine balance off and feel like a misfire. Once the damper is replaced and the balance is corrected the engine will idle smooth again.
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Customer: replied 2 years ago.

Then how would it show misfires in the data on the scanner during the contribution test?

Expert:  James replied 2 years ago.
An engine vibration can be seen as a misfire even if it's not.