Misfire? Running rough around 50 mph and 12 to 1500 rpm? - Chevrolet Forum - Chevy Enthusiasts Forums

Misfire? Running rough around 50 mph and 12 to 1500 rpm?

Old  September 27th, 2011, 6:24 PM
  • CF Beginner
    Join Date: Aug 2010
    Posts: 5
Misfire? Running rough around 50 mph and 12 to 1500 rpm?

My 2001, 150000 miles, Sub just started running a bit rough, possibly a misfire, but not sure? Around 45 to 50 mph, 1200 to 1500 rpm, most pronounced going uphill, engine seems to skip, run rough, misfire?, If i downshift it doesn't seem to do it? Normal idle and low speed, smooth running. There isn't any check engine light on. I thought about plugs and new wires, but some of the stuff I have read here doesn't really back that up as a solution. Possibly and O2 sensor although I thought I would get a check engine light for something.

Does anyone have any thoughts or recommendations before spending a $1000 with mechanic checking things of the list. Thanks in advance for any help!!

Old  September 28th, 2011, 12:16 PM
  • CF Veteran
    Join Date: Aug 2010
    Posts: 1,053
    New York City USA
may be a pending code in the computer...scan to see.

Old  September 28th, 2011, 8:35 PM
  • Administrator
    Join Date: Apr 2008
    Posts: 7,229
    Austin, Texas
2001, 150K miles I'd start with a good clean tune up...run a few bottles of injector cleaner, check the fuel pressure... clean up the MAF sensor...

Old  October 3rd, 2011, 10:58 AM
  • CF Active Member
    Join Date: May 2011
    Posts: 189
Hook up a vacuum gauge and read THIS.

Old  October 3rd, 2011, 7:07 PM
More pronounced going up hill... might be the catalyst stopped up.

Old  April 14th, 2013, 8:48 AM
My 2005 z71 does the same thing except hills don't seem to affect it

Old  April 18th, 2013, 8:37 PM
  • CF Senior Member
    Join Date: Mar 2013
    Posts: 406
ummm yeah. you got clogged cats if you have zero vacuum....

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