I have a loss of power (no increase in speed, etc) when stepping on the gas pedal and transmnission downshifts to a lower gear at say 60 mph. Transmission will downshift OK but engine seems out of power and cannot increase speed. This power is needed when coming onto a freeway onramp to match existing vehicle speeds. This has never been a problem in the past and I've already put in a new air filter and fuel filter. Could a plugged catalytic converter be causing this problem with no OBDII codes showing?
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2002 Chevrolet Impala
Question: Loss of power when downshifting at highway speeds. Plugged catalytic converter?
Answer #1Greg's Orange Auto (8341 Answers) , Orange, CA - (714) 361-9355globalhelper November 14, 2012, 12:56Master
DO U HAVE ENG CODES AND WHAT ARE THEY AND YES A PLUGGED CATT WILL CAUSE LOSS OF PWR
Replyvettewine, November 14, 2012, 13:34Rookie
As I said in my original post, no OBDII codes were triggered. I talked to an ASE service tech at a GM dealership and he said there should have been codes triggered if the catalytic converter was to blame. He suggested either dirty injectors or poor fuel as the stations locally have just changed over to the winter blend which is of poor quality. They are seeing lots of complaints about this.
Replyglobalhelper, November 14, 2012, 17:58Master
a plugged catt will not ALWAYS SET A CODE. I THINK YOU SHOULD GO TO AN EXH SHOP AND CONFIRM CATT IS GOOD B4 WAASTING YOUR MONEY
Answer #2ziptie12 November 15, 2012, 18:05Master
Agree with globalhelper. If able to , bring in and have the tech you talked to diagnose it. See if the story doesn't change when he stands to make money on it. Also , restricted exhaust will NOT always set code(s) as GH stated before. Good luck.