#boom

Andrew writes:

Hi Sajeev,

I’m trying to wring a few more years out of my 1994 Geo Prizm, and recently the engine got louder. It’s a very low end bass like sound that makes the whole car vibrate a lot more.

The muffler and resonator are relatively new, and the noise seems localized to the front of the car. What’s odd is that the engine is the loudest when it’s idle. As soon as the RPMs go above 1500, the engine is only a little louder than it normally would be. How do I find out if the problem is the exhaust manifold, or the downpipe from the manifold to the catalytic converter? Over the summer there was a brief time when coolant was leaking and dripping down onto that downpipe and burning off. That leak issue was addressed, but that downpipe has some rusty sections on it anyway.

Sajeev answers:

There is a war of opinions over the direction of the Chinese car market. Bloomberg says that “China’s auto sales may fall 10 percent this year with the end of government stimulus policies and restrictions on car licenses, according to the China Automotive Technology & Research Center.” Bloomberg’s colleagues at Reuters called Chen Hong, President of China’s largest automaker SAIC as a witness. He expects the Chinese car market to grow 7.4 percent to end up at 19.7 million units by year’s end. Who’s right? Who’s wrong?