Rough Idling

  • 2005 FORD RANGER
  • 197,000 MILES

I have had my Ford Ranger to two different garages for a rough idle diagnostic. Both put the scan tool on and found misfiring on two cylinders. The local Ford dealer said they did an air pressure test and found low compression on two cylinders. Both shops suggested that an engine replacement was the only repair. What other options may I have for this problem and a potential repair.

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Friday, April 19th, 2013 AT 8:28 PM

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  • 26,795 POSTS

Assuming a compression test showed low compression on two cylinders and the test was done properly, the next step would be to do a more involved cylinder leakage test. By looking and listening, that will tell if the leakage is through the intake valve, exhaust valve, past the piston rings, or through a leaking cylinder head gasket. You also didn't say how much those two cylinders were low. There are other potential causes of low compression. Either valve could be not opening fully due to a worn lobe on the camshaft or a broken rocker arm. For things like that you don't replace an entire engine with a used one that could have the same problem waiting to occur. You would typically repair what is broken. Have the cylinder leakage test done first. It takes quite a bit longer but I would want to know WHY I'm replacing the entire engine before I agreed to that.

'96 and newer models have misfire monitors in the Engine Computer as part of the emissions package and there should be diagnostic fault codes stored in the computer indicating which cylinders are responsible for the misfires. Did anyone read those codes? The Check Engine light should have been on too. Do those codes indicate the same cylinders as were identified in the compression test?

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Friday, April 19th, 2013 AT 9:13 PM

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