Fix my own car? I think not

I love my 2004 Nissan Maxima. Although it is approaching its 5th year in my garage, I still consider it my new car.

I decided to replace the engine air filter last Tuesday. I did that regularly on the '51 Chevy I drove in high school, but recently I have just let the dealer do things like that at oil change time. It was pretty easy on the Chev. There was a big metal cylinder at the top of the engine. I would just remove the wing nut that held the top on, remove the top, pull the old cylindrical filter out, plop a new one in, and replace the top and wing nut.

When I read the owner's manual, the task looked almost as easy on the Maxima. The filter is flat and rectangular. It is housed in a plastic box. The box lid is molded to the hose that feeds the air into the intake manifold. First, I loosened the clamp that secures the hose to the manifold. Then I removed the connector for the temperature sensor from the hose. Next I unfastened two spring clamps that held the lid on the box and rotated the lid and the hose until I could slide the lid off. Then I exchanged the new filter for the old one. I put the lid back on, fastened the two spring clamps, reattached the temperature sensor (I thought), and tightened the hose clamp.

The engine started fine. But when I shifted into drive, it seemed like the engine had no power at all, or perhaps like the transmission was slipping. I knew it wasn't the transmission. I had done something wrong when I replaced the air filter.

I turned off the engine and checked my work again. Aha! That temperature sensor was not snapped securely into place. After I fixed that and re-started the engine, everything seemed to work fine.

Then the "service engine soon" lamp lit on the dashboard. Now that usually comes on when you forget to put the gas cap back on. The lamp indicates problems in the pollution control system. When you put the cap back on, the lamp goes off after a few minutes of driving. I assumed the same would happen after I replaced the air temperature sensor--WRONG--it remained on.

So, off to the dealer I went. They attached their computer to the Maxima. They determined that the temporary lack of an air input temperature sensor "confused" the engine's computer so that it could not set the engine idle correctly, and so that it lit the lamp. The technician let the engine cool down a little, and then reset the computer for proper idling and to turn off the lamp. All of this was done in just two hours for a fee of about six times the cost of the filter.

My '51 Chevy worked fine without a computer or an air intake temperature sensor. When I started the car, I pulled out the choke, and when the water temperature gage showed that the engine had warmed up, I pushed the choke back in. I was the computer. And I could replace the air filter without collateral damage.

Now I know the correct way to replace the Maxima's air filter. But I will probably not do it again. I won't try to replace the spark plugs or adjust the timing either.

I also understand why the manufacturers place a big shroud over most of the engine and its parts. It looks fancy, but a little intimidating. They don't want putterers like me confusing their computers. They win.