2005 Mileage and Exhaust Popping

[sbyun]

Hi All,

I have a July build 2005 MCS

First 300 miles: 29 mpg, no exhaust popping/bubbling noise (lots of threads about that)

Next 300 miles: I had a crack in the supercharger intake duct, SES and EML lights the whole time. By the time I got the service appt and the duct was fixed, I had averaged 20 mpg (but still no exhaust popping)

Most recent 100 miles: The intake duct is fixed, but my mileage is only ~22 mpg. The exhaust popping is VERY pronounced, and occurs as low as 2300 rpm, even if I don't abruptly lift off the throttle. Sometimes it sounds like old-fashioned backfiring, not a cool bubbling/popping sound. There are no engine lights on.

I called service today, wondering if maybe the fuel mixture was too rich, causing the backfiring and poor mileage. The service rep told me that nothing is adjustable on the MCS - the engine computer handles everything, adjusting the fuel mix 10x per second. He suggested driving as-is for 2000-3000 miles, to see where the car settles in. I explained the terrible mileage I was getting, but he said that could be due to the horsepower increase for 2005 (I don't believe that).

What do you think? Should I take my car in to get checked out? Given that there are no engine lights on, is there anything a tech would be able to do?

Thanks!

[Dave&Stacy]

After we had our intake pipe fixed, we experienced a similar issue. We have to drive 140 miles for service. We noticed when we first picked it up after the fix, that it popped a ton. On the way home that day, we only got 26-27 mpg (instead of our normal 30+) on the highway. Now we have put an additional 300-400 miles on it since the fix. Everything has smoothed out. Less popping and the mileage is back to around 30 mpg. Give it another 200 miles and see what happens. If it doesn't improve, take it back in.

-Dave & Stacy