Slow Acceleration on 2003 Volkswagen Jetta

I'm having a problem every so often that my Jetta's acceleration responds very slowly. I have had the car for a year, and it has 118,000 mi. on it. I've put on about 10,000 of those. I have not had this problem much before except a month and a half ago when I had to replace the Mass Airflow Sensor. The engine made a very loud rumbling noise at the time, which has not made since and is not making now. Right now it's just ocassional sluggish acceleration. I can make it accelerate faster by really punching the gas, but that makes the car shift really hard and the tachometer really jump. It has been about 0 degrees F lately (it's January in Minnesota), but I've started it up at -20 F without problems before. Any suggestions on the sluggish acceleration?

by in Saint Paul, MN on January 08, 2011
1 answer 1 comment
ANSWER by on January 11, 2011
Was the Mass Air Flow Sensor a dealer part? Because if the number is not matched EXACTLY your car will not run correctly, and you may need a software upgrade for the new Sensor. I do Emissions Diagnosis and repair work in Calif. I do this stuff for hours, all week long, and this is what works.
COMMENT by on January 12, 2011
I am taking the car in today. I will check to make sure that this was the case. If not, or if I continue to have to problem undiagnosed, I will have to take it to another mechanic. Thanks very much. This has been very helpful.
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