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Greetings. 2009 Mercury Mariner Mariner P0302 code. I am sure most of you have dealt with this before. So far, he is what my mechanic has done:
--replaced all valve cover gaskets
--replaced spark plugs and boots on coil packs
--compression test on all cylinders, with all coming in at 120
--checked all fuel injectors
--switched coil packs on #2 and #4 to see if the code would be P0304 signaling that it would most likely be the pack
The car is sluggish when idling in drive, and also around 45-55 mph
Any other items that should be checked? It's a great vehicle-- has 178K miles on it and the transmission has around 90K on it.
The code won't change immediately. Do a cylinder drop test you can unplug 1 coil at a time until you find the cylinder that isn't firing. (it may not be number 2 companion cylinders can flag incorrectly) after pinpointing which cylinder it is move the coil and or plug to another cylinder and do cylinder drop test again if it follows coil or plug then you know what it is if it does not follow then you could try same thing with injector or verify wiring integrity
Ben wrote: The code won't change immediately. Do a cylinder drop test you can unplug 1 coil at a time until you find the cylinder that isn't firing. (it may not be number 2 companion cylinders can flag incorrectly) after pinpointing which cylinder it is move the coil and or plug to another cylinder and do cylinder drop test again if it follows coil or plug then you know what it is if it does not follow then you could try same thing with injector or verify wiring integrity
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Just talked to the guy that worked on my vehicle, and he says they did that. Any other suggestions? Could it be electrical, wiring, etc.? Thanks again for your response.
For clarity, which engine does your Mariner have? You said valve covers, suggesting the 3.0L, but I want to be sure.
If it's the 3.0L, then #2 is the underneath the intake, correct? Is that the coil that your mechanic has been moving around, or was it a different one?
It is a 2.5L 4cy. Some more information: once the vehicle is put into drive, and it idles, I can feel a shudder. When the vehicle gets up to 50-55mph, then I feel a much harder shudder. Replaced ALL coil packs, and it didn't change anything. Same code registered, and it continued to shudder. Any chance it could be the torque converter?
I doubt the TCC is at fault here, especially because you're feeling a roughness at idle. If you're not convinced, you can get the engine shuddering at 50 MPH and tap the brake pedal with your left foot while keeping your right on the gas. If the shudder remains, it's not the TCC.
I say back up and come at this from scratch. Get someone else in the driver seat and get the engine running rough in drive. Go out to the engine and do a power balance test to make sure #2 is the weak cylinder.
While you're there, do a quick audible relative compression test. Your mechanic measured 120 PSI on all cylinders, which sounds low to me. Floor the gas and crank the engine, listen for a skip. Take a phone video and post if it you're not certain.
How were the injectors checked, exactly? Consider moving #2 to another cylinder if the power balance test works out and the relative compression shows no issues.
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