Hi,

This must be a simple problem, but I cannot figure it out: since this summer my Camry engine (Camry 99, 2.2 L 4 cyl EFI) has louder hum than normally. I began to notice that the acceleration was a bit more difficult (i.e. "weak") after I replaced the tires; but assuming the tires are properly inflated, I don't think this is related. But read on. One time, I backed up from a ramp and the tailpipe hit the ground. Right after then the engine hum become loud, unusually loud for a car like Camry. (Just think of the usual engine hum, but make it louder). The loudest hum that we could hear from the driver's seat was at 2000 rpm.

There are two other symptoms accompanying this problem. First, the car's acceleration became weak, like the car is having little power. It took more push on the accel pedal (and higher RPM) to accelerate as usual. At the same time I noticed that the gasoline consumption became high. I have a record of car gasoline fillup+mileage; usually I could get ~25 mpg in town+some highway and almost 30 mpg all-highway. Now it ranges only between 22-25. After some weeks of loud hum, the engine hum suddenly diminished (not fully going away though). Now we can still feel that the hum is abnormally high, albeit slightly. But still at 2000 rpm the hum was louder than at other RPMs.

About 2 month ago the engine felt like having no power at all, and a friend recommended us to clean the combustion chamber using fuel system cleaner. I got one from Wal-Mart (I forget the brand now). Immediately after applying the cleaner, the power got restored, but it did not improve a whole lot.

I brought my car to my mechanic, and he replaced the fuel filter. But the weak power+bad gasoline consumption problem haven't gone away. The next time I asked the car to be test-driven; yet the mechanic said that the car drove OK. I am puzzled. He did not recommend the professional fuel system cleaning, or tune up, or what.

What could be wrong with my car? I am afraid if mechanics would try to offer me this and that service which does not cure the real problem immediately.

Wirawan

Check the exhaust system for leaks. Have your mechanic raise the car on the lift with the engine running and then hold a rag over the end of the tailpipe. If there is an exhaust leak, this simple test will make it easy to find.

As far as the reduced mileage is concerned, the drop in temperatures could account for the slightly lower mileage. Check your mileage readings from last year at this time, and also January and February. In my area it has been an extremely cold December, more like January and February. The temperature in Chicago right now as I type this is -3.

Mike

Hi,

One time, I backed up from a ramp and the tailpipe hit the ground. Right after then the engine hum become loud,
There are two other symptoms accompanying this problem. First, the car's acceleration became weak,

Wirawan

If the exhaust system was damaged such that back pressure was increased, this would explain the loss of power.
Have the mechanic connect a vacuum gauge and run the engine around 2,000 rpm. The vacuum should stay constant, not drop. Decreasing engine vacuum correlates with increased exhaust pressure, which will not allow the engine to "breathe" properly or run correctly.