QuestionQUESTION: Hi. Hope that you can help me. I own a 2002 Infiniti I35 - same mechanicals as the Maxima. The check engine light has come on and off intermittently. I had AutoZone hook up a scanner and the codes read P0011 and P0021; I was told that these codes relate to a fault with the camshaft position sensors. I replaced the front sensor but the light came back on after being off for 6 weeks. Is it the other sensor or could it be a simple short? I notice also that when I change the oil the light goes off after a couple of driving cycles. Thanks.
ANSWER: Sean,
The codes relate to the intake valve timing control. This is not the camshaft angle sensor or the crank angle sensor. Basically, Nissan uses variable valve timing and what is going on is the variable valve timing is sticking. This was a problem on older Nissan cars. After 1999 the problem was pretty much corrected. Now, you say that after the oil was changed the problem goes away for a time. Just to let you know, the variable valve timing uses oil and the variation in oil pressure to advance and retard valve event timing. What this means to you is that your oil is probably dirty, gummed up, and the oil galleries are clotted. I would first change to Mobil 1 Synthetic 5W30 and see if that clears it up. It will probably take two changes to get it cleared up. If this does not do the trick you will end up having the valve covers taken off and the eccentric cams removed and cleaned or replaced. So, hope the oil changes do the trick. I would change the oil and drive it for at least 1000 miles and then change the oil again. Also, if the car is not running at operating temperature change the thermostat. A cold engine, as in a bad thermostat, will cause the oil to gum up since it never reaches temperature. So, be sure to see if it is running at normal temperature. Also, on the thermostat, purchase it from Nissan. It is really expensive at the dealer, but courtesynissan.com is a place you can get a thermostate at a reasonable price. The Nissan unit includes the thermostat neck and the thermostat is screwed to it. If you are going to get one be sure to get the gasket too, since it does not come with one.
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QUESTION: Thanks for the advice. I will try the synthetic oil changes first but if it does not work I am not sure that I will remove the cams that you describe because that sounds expensive. Could the issue be resolved with a engine flush? Last night, the light went off again.
ANSWER: Sean,
Depending on how much sludge is in the engine it could prove to be bad to use an engine flush. Now, if you have done regular oil changes and the oil is just a little gunked up you could do a quick engine flush followed by fresh oil and see how it does. Your choice here.
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QUESTION: Thanks for your quick reply. I purchased the car @ 114k, now has 120k. I went to the repair shop that the previous owner used and according to their service records the guy kept up on the oil changes. I have done two oil changes since buying the car and I am pretty religious about maintaining my cars. According to the service records, at 97K the engine light was on and the shop noted code P0011 but stated that it occurred because the engine was 4 qts. low on oil. Anyway, I'll do the oil changes; I am now afraid to try the flush.
AnswerSean,
I would just change to Mobil 1 5W30 synthetic and see how it does. The synthetic does an excellent job of cleaning up the internals of an engine. But, it will probably take two changes to get all the gunk out. The first change should be run a thousand miles or more and then change it again and see how it goes.
