Mercury Mountaineer 4.0L Misfire

Matt Manager Missouri Posted   Latest   Edited  
Case Study
2007 Mercury Mountaineer 4.0L (E) 5-spd (5R55S)

Hello all,

Customer bought this vehicle like this they had fired the parts cannon at it. I looked at primary, secondary and injector waveform. It all looked good. So I did an in cylinder and this is what I got. I’m thinking maybe a valve seating issue? 

Any help would be great. Tia. 

Joel Diagnostician

if it is valve not seating I would say leak down test, but reason for not sealing if intermittent as we can see here will be valve spring rigth? or you are not capable to open the valve because of collapse lifter, ither way tear down and get a combo ,machine shop , I will suggest to replace all exhaust valves .

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Albin Diagnostician

You are on the right track. Your waveform one of the valves isn't seating too well. If you want to pinpoint which one, use FLS in the intake and exhaust to find the valve. Either way, the valve cover is going to come off, take a look at the valve springs, If no springs found broken, then go on in deeper to the cylinder head.

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Matt Manager

Thank you guys. That’s the track I was heading down but I always like a second opinion when I’m. not sure.

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