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Mike V.
Mike V., Nissan Technician
Category: Nissan
Satisfied Customers: 23626
Experience:  Nissan factory trained and Certified Subaru Technician.
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Nissan/Datsun Altima S: I have a 2006 Nissan Altima s 2.5 with

Customer Question

I have a 2006 Nissan Altima s 2.5 with a rough idle in gear problem. About 3 months ago I got a p0303 code so put my scanner on it and checked everything out. I removed #3 plug and it looked good,I removed #4 and it had oil in the plug tube. I removed the oil and replaced the plugs and valve cover. I put NGK plugs in and a dorman valve cover on. The car smoked after warm up like the head gasket blew. I found the aftermarket valve cover was no good so I went to Nissan and got a new one. The smoke went away and the car seemed fine,after about a month the car started vibrating in gear with foot on the brake and when started after warm up or when cold it would start but act like it wanted to go dead. The DTC light didn't come on until a couple of weeks ago. Same code p0303. Thought maybe the head gasket was a problem so I checked compression I had 180 across the board,I checked with the combustion detector and fluid,came back negative. The interesting thing is I'm losing coolant somewhere but don't know where. The heater core looks ok the water pump isn't leaking out the weep hole and I've looked in the cylinders with a bores cope and nothing. I'm at a loss,the only thing I haven't checked is the injectors,wiring, or vacuum leaks. This is a cop ignition and they look ok. I moved #3 to #1 and I got a p0300.
Submitted: 6 months ago.
Category: Nissan
Expert:  Mike V. replied 6 months ago.
Hi there,It is likely the head gasket causing the grief sorry to say.The best method I have found for testing these is to do a pressure test on the cooling system. Pump it up to about 15psi and leave it for about an hour. Then, pull the plugs and look into the cylinder with a flashlight. Most of the time you will see the coolant sitting on top of the postion. This is why the compression test reads find AND there isn't any exhaust present in the coolant. It actually leaks in, then burns out. As the leak gets bigger then the code comes back. This is because it takes a little longer for the piston to push all the coolant out through the valve.Hate to say it, but this looks like a problem with the head gasket as you are losing coolant without any visible signs, and you have the misfire code.Please let me know what more I can do to assist you today. Also, please remember to rate my answer, Just Answer does not compensate me for my time and resources. Follow up questions are included in the price of your question. If you are using the free trial, or have a subscription a rating is still required.Thank you so much!