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Topic
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I have a 2008 Nissan Altima 2.5 6 speed with 220,000 miles that has developed a vibration at 2K RPM regardless of what gear it’s in. It even vibrates when in neutral, but only at 2K RPM. I have no trouble codes and new spark plugs. I did a power balance which revealed no issues. The compression showed 165-167 PSI in all four cylinders. I have replaced all motor mounts and the transmission mount.
Now for the embarrassing part. About a year or so ago I installed an aftermarket lightweight crankshaft pulley, eliminating the harmonic dampening factory pulley. About a month ago when I started noticing the vibration, I switched back to the factory crank pulley which had no effect on the vibration. How probable is it that damage was done to the crankshaft or crankshaft bearings, and how would I determine that this is in fact the case? What else could cause the vibration if the pulley isn’t the culprit?
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I doubt the bearings were affected by the pulley change, except for maybe crank thrust bearings, but still doubtful. A more likely source of the vibration would be pertaining to the balance shaft(s).
This issues was resolved by removing my aftermarket under-body (downstream) catalytic converter and replacing it with the old factory one. I guess the aftermarket one hit resonant frequency at 2K RPM or something, it’s just odd that the vibration took so long to develop, since I installed the aftermarket cat over 6 months ago. It was a cheap (maybe $140) replacement part that I got at Autozone after the flex pipe on my factory cat become extremely corroded. So glad to have this issues resolved and know that I didn’t trash my engine!
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