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Q: Engine noise when cranking. P0011 and P0021 codes

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I have a 2004 Nissan Altima 3.5. I had an obd code p0011 & p0021 I believe. I did some online research and changed my oil and reset the check engine light. Now on a cold crank my engine rattles (or knocks) for like 3 seconds then stops. I never hear it again until the next morning when i get ready to go to work. Can you tell me the problem and what course I need to take to repair it

My car has 104000 miles.
My car has an automatic transmission.

A: Hi there. The P0011 OBD-II error code indic...

Hi there. The P0011 OBD-II error code indicates that you have an over advanced timing issue, which might be the reason why your engine stumbles for a brief moment when it's cold and first starts. Ignition timing is typically monitored by the crankshaft position sensor, which may be the source of this error code and the cold starting issues. However, it could be multiple electrical or even fuel-related issues that are causing the rough starting problem. To know for certain, it's a good idea to contact a professional mechanic to complete an engine is hard to start inspection so that this can be properly addressed.

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