Nissan Repair: 1998 Nissan Maxima, haynes manual, planetary gears

Question
Von I am experiencing problems with my car again. When I start the car at times it starts perfect. When it reach a temperature it would develope a dragging starting problem as if the battery is low. I did a scan and found it was the knock sensor. That was changed and the same dragging experience when starting the car after it reach a temperature continues. This does not happen all the time when starting the car after it has a temperature. I scan the car again and got a p0135 reading which is a oxygen sensor. I check the haynes manual and it is saying this sensor have something to do with voltage. Is this my problem or what. Please remember sometime ago I did a rear timing cover oil leak job and after I put the car back up I allowed a friend to install some aircondition parts and he told me how the car was dragging at starting and he believe i might not have put the timing back the way the factory had it. I followed the haynes guide lines when putting the engine back up and it started on one crank. Now if this is a timing problem shouldn't the car drag continuously on starting? And wouldn't it have done so when i first put it up? Could this also be a starter problem? I really want to have the car right before i give it to my wife.PLEASE HELP.

Answer
Kingsley,

First, the timing should be correct if the car starts and runs fine.  You can check static timing by running the engine over to top dead center and checking the position of number one cylinder and the valve event for the intake valve.  It should just be opening.  But, that not withstanding I would say the starter is going out and once the engine gets hot the starter does not want to turn the car over.  You can take the starter out and disassemble and lubricate the planetary gears adn reinstall.  I get several years more use out of a starter doing what you describe.  The oxygen sensor thing is just a matter of replacement of the correct one.  Yes, yours are heated as this makes them work faster during warmup.  It is a smog thing that the manufacturers do to get the car under computer control faster.  I would replace all the oxygen sensors as this will make the car run better and get better fuel mileage since they should be replaced every fifty thousand miles.  Most people run them to failure and I am guilty of that too.  So, you could only replace the offending one and be done with it for a while.