2009 Mercury Mariner Misfire

Tiny
COWBOYSING
  • MEMBER
  • 2009 MERCURY MARINER
  • 2.5L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 172,000 MILES
We recently took our Mercury Mariner to a Ford Service Dealer. First because the steering went out which cost $1300.00. Then it was running rough so we had $250. To put plugs and a coil in.
Now the engine light is on and when we took it back they ran the scope on it and they said it was a head gasket and would cost $3000.00 and we should just trade it in on a new one.
I'm not sure I believe them. There is no oil leak, steam coming out of the tail pipes or water in my oil. So I ran a diagnostic myself. With an Actron Pocket Scan. I God a Code P0302 "Cylinder 2 Misfire Detected" and a Pending Code of the same.
My question is can a mechanic tell if it's a broken head gasket from that or is there other things that I can do myself?
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Wednesday, January 29th, 2014 AT 7:56 PM

3 Replies

Tiny
CARADIODOC
  • EXPERT
$1300.00? The steering is a system made up of a lot of parts, and you never need to replace everything. I'd think twice about owning any car that can cost that much to repair something with the steering. That bill would make a GM dealer proud.

The diagnostic fault code only tells you the problem the Engine Computer detected, but it doesn't provide the cause. As you can see too, they never say to replace parts or that one is bad. They just indicate the circuit or system that needs further diagnosis, or the unacceptable operating condition.

A leaking cylinder head gasket is always a possibility, but if you're not losing coolant, I'd eliminate the more likely possibilities first. This is going to be easier since you have a scanner. Start by switching the ignition coils between cylinder 2 and another one. Erase the fault code, then see if a code sets again for cylinder two or the one you moved that coil to. Ford seems to have quite a bit of trouble with their ignition coils, so if the misfire moves to the new cylinder, replace that coil. The next step would be to do the same thing with two injectors.

Woops. I gotta back up a minute. I suspect that code you got was left over from the spark plugs and ignition coil. I just reread your post. To get back to the head gasket, there is a real fast chemical test to see if combustion gases are sneaking into the cooling system. That involves drawing air from the radiator while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow.

You may be able to borrow this tool from an auto parts store that rents or borrows tools, but they usually make you buy your own bottle of the fluid. It is rendered useless if it freezes or gets contaminated with antifreeze. That could yield inaccurate results for the next person.
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Wednesday, January 29th, 2014 AT 9:05 PM
Tiny
COWBOYSING
  • MEMBER
Thank you! I will try that last test you talked about too!
On the steering. They said that they had to replace the whole steering column because there are module's in there that don't come out (I quess) that have to link to the steering box. This unit is electric and uses no fluid :(
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Thursday, January 30th, 2014 AT 7:41 AM
Tiny
CARADIODOC
  • EXPERT
I see. I DO know that Nissan has an electric rack and pinion assembly that cost over $5000.00. I'd sure want to know that before I bought one of those cars. $1300.00 doesn't look so bad now.
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Thursday, January 30th, 2014 AT 12:04 PM

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