I posted this same question on Maxima.org, but no answer yet...
I'm posting this message for a family friend, so this is not my car.
She has a 91 Maxima Brougham with the V6 motor. It has 69000 km (44000 mi) on it. She is experiencing power loss and rough engine vibrations after driving the car for 10 minutes after a cold start. Stopping the engine for about 10 minutes and restarting seems to correct the problem for the rest trip until the next time this is repeated. Loss of power is most noticable when climbing a hill, but has also been noted on level road driving.
The local Nissan dealer recently performed a major emmision service along with a timing belt, cam seals and welsh plug change. Although the problems seemed to disappear for a couple of months, they have returned as before. Keep in mind that this car is not driven alot.
I don't think the timing belt was the problem, but I assume the dealer had guidelines to follow for replacing it. I have read that the O2 sensor may be at fault, but the symptoms from those posts were slightly different. Still this may be the culprit. Any ideas? I think this is a great car and it would be a shame for her to sell it.