[YeeKung]

Hello,

I've been reading posts about check engine lights, with code PO172 and I have the same problem. I've been having trouble codes PO172 and PO175 setting (now PO172) for the past year. Also, the car would idle roughly, exhaust vibrate, when I'm at a stop light. To stop this, I would put the car in neutral or press on the gas a little. Sometimes the car would hesitate when I accelerate from a stand still. The first time the check engine light came on, I had PO175 and my dealer told me because I was low on oil. I'm no mechanic expert, but I found it hard to believe. I had the oil change and all was fine for awhile. Since then, the check engine light has gone on and off and in the last 6 months, now stayed on. I've had my spark plugs and air filter changed. After reading many posts, I cleaned the MAF sensor with electronic cleaner yesterday and the car would idle much more smoothly and no hesitation. After driving the car for 13 km (8 miles) the engine light came back on today and is still on. Hesitation has come back too. A mechanic told me that it is possible that I have a blockage in my exhaust system, possibly muffler, that would cause the hesitation. I'm thinking of changing the muffler, but I would like to make sure it is a cause of my problems (or some). I'm also thinking of changing the O2 oxgen sensor too, but a lot of posts says it is not likely the culprit. Everything in my car is stock, no performance parts of anykind. Any help would be greatly appreciated.

Thanks.