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Discussion Starter · #1 ·
I am dealing with these two issues.

I replaced radiator in March and since then, the temperature gauge has been maxing out every so often for a few seconds but then would drop back to normal like nothing happened. I checked coolant level Friday and i added about a quart. I rented a tool today and pressure tested it. Pumped to 12 PSI and watched it for about 5 min. It held. I did not drop one bit. I checked for coolant under the dash and hose connections in the engine bay. Did not see any. I don't know if that eliminates any leak in the cooling system.

P0302 happens just about every day and only when i start the engine and doesn't matter if engine is cold or hot. I recently replaced coils and plugs but i swapped out #2 with the old ones i saved. First the coil, still did it. Then the plug, still did it.
This is a pic of the #2 and #4 plugs for comparison. Maybe you see something different.
20210607_140225.jpg


Here's a comparison of the #2 (top) and #4 (bottom) cylinders. Big difference but I don't know what that tells me. #2 looks oily while #4 looks dry.
Any input will be greatly appreciated. Thanks.
 

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It's your coolant temperature sensor I believe is going bad or there is a bad connection. Clean the connections. If the sensor goes bad indefinitely you should get a check engine light. The computer can make the fuel mixture richer in some cases. I cannot explain the difference in the pistons. Aftermarket not that expensive . See what happens when you change it . Report back
 
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Discussion Starter · #4 ·
I added coolant Friday. Burped it some more yesterday after checking for leaks. It took in probably another 2 cups of coolant. The coolant overflow reservoir level stays. Did not drive it all weekend until today. Drove a little over 200 miles today with a lot of idling time in between. Temp gauge did not spike and no misfires either.
As far as the oily looking #2 piston, could that be leaking head gasket or worn out rings?
 

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The temp sensor is located up high so being a quart and a half low on coolant could very well cause the temp gauge to spike when the sensor is momentarily no longer surrounded by coolant.

The plugs look fine. I'm with Paul R in that I don't know what to make of the darker colored #2 piston. A leak down test is the only positive way to test for a bad head gasket. Fortunately #2 is in the front and easy to get to. I think I'd do a leak down on 2, 4, and 6 to rule out that the P0302 is caused by a leaky HG.
 

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Discussion Starter · #6 ·
I'm gonna have to research how to do a leak down test and figure out what tools i need. For now, I'm trying fuel injector cleaners per Paul's suggestion. It may just be a dirty fuel injector. Just added a Seafoam High Mileage one then I'm trying GUMOUT brand in the next fill up.
 
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