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

kronzy's Avatar
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Join Date: Aug 2010
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September 27th, 2011, 7:24 PM   #1  
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!!

RacerX's Avatar
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New York City USA

September 28th, 2011, 1:16 PM   #2  
may be a pending code in the computer...scan to see.

in2pro's Avatar

Join Date: Apr 2008
Posts: 7,405
Austin, Texas

September 28th, 2011, 9:35 PM   #3  
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...

slw210's Avatar
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October 3rd, 2011, 11:58 AM   #4  
Hook up a vacuum gauge and read THIS.

loosebearing's Avatar
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October 3rd, 2011, 8:07 PM   #5  
More pronounced going up hill... might be the catalyst stopped up.

hoghunter03's Avatar
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April 14th, 2013, 9:48 AM   #6  
My 2005 z71 does the same thing except hills don't seem to affect it

Joe In NY's Avatar
CF Senior Member

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April 18th, 2013, 9:37 PM   #7  
ummm yeah. you got clogged cats if you have zero vacuum....

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