Why is my motor idling rough???


Asked by May 28, 2014 at 11:10 PM about the 2002 GMC Sierra 2500HD 4 Dr SL Extended Cab SB HD

Question type: Maintenance & Repair

I have the vortec 6.0 v-8, and sometimes when I start it the check engine light will flash and it will idle very rough, and then when I put it in gear and try to accelerate it will bog down for a few seconds until I get it over 1600-2000 rpms. And then the check engine light will flash once and a while while im driving and the acceleration will not be as responsive and it sounds like it may be misfiring. Any ideas? Mass Air Flow Sensor maybe???

2 Answers


Could be mass,but the best way to know for sure is take it and let some one hook it to obd reader,any parts store can do this for free.


How many miles are on it .I have 2002 avalanche and I had the same problem and GM are known to have fuel pumps go out around a 100,000 miles, that was my problem .Take it to get the fuel pressure checked that will tell you if the pump is bad. If so GM put it inside the fuel tank pain in the but to replace you have to pull the tank. Cost about 700 dollars to have it replaced.

Your Answer

Add photo

Related Questions

  • 2002 GMC 2500hd rides rough except when turning right 3 answers

    GMC Sierra 2500HD


    Maintenance & Repair

  • Rough idle 9 answers

    I have a 99 Yukon with a 5.7L vortec engine. It had a slight knock since we bought it but it never was a problem. We had some out of town trips planned for this summer so we figured we should fix ...

    1999 GMC Yukon SLE 4WD


    Maintenance & Repair

  • rough idling 3 answers

    why does my 98 Sierra idle rough between 1st and 2nd gear,? it's 2wd runs good once it gets out of 2nd,gears switch right on with the rpms at 2,500. what could our be.?

    1998 GMC Sierra 1500 C1500 SL Extended Cab SB


    Maintenance & Repair

  • 1990 GMC Sierra idling rough and guzzling coolant. Why? 11 answers

    Truck has started idling really rough when, say, stopped at a light. The idle continues to be rough when I pick up speed, but it tends to even out a little. On top of that, my coolant has been disap...

    1990 GMC Sierra 1500


    Maintenance & Repair

  • 2004 Envoy XL Rough Idle 5 answers

    I have a 2004 Envoy XL and it idles rough when in Drive. No other problems other than the rough idle. I took it to a mechanic and he noticed what I was talking about but couldnt find anything wrong ...

    2004 GMC Envoy XL SLT


    Maintenance & Repair

Search GMC Sierra 2500HD Questions

GMC Sierra 2500HD Experts

#1 FordNut
Reputation 130
#2 jeremyd12
Reputation 110
#2 iEATricers
Reputation 110
View All

Related Models For Sale

Used Chevrolet Silverado 2500HD"
400 Great Deals out of 33,541 listings starting at $2,499
Used Ford F-250 Super Duty"
441 Great Deals out of 42,971 listings starting at $2,250
Used GMC Sierra 1500"
1,025 Great Deals out of 56,906 listings starting at $2,300
Used Dodge Ram 2500"
151 Great Deals out of 5,741 listings starting at $2,289
Used Chevrolet Silverado 1500"
2,448 Great Deals out of 144,749 listings starting at $1,995
Used Ford F-150"
3,272 Great Deals out of 216,641 listings starting at $1,500
Used GMC Sierra 2500"
224 listings starting at $2,895
Used Ford F-350 Super Duty"
442 Great Deals out of 26,916 listings starting at $2,999
Used GMC Sierra 1500HD"
6 Great Deals out of 124 listings starting at $3,450
Used Toyota Tundra"
618 Great Deals out of 26,786 listings starting at $2,500
Used Chevrolet Silverado 2500"
3 Great Deals out of 272 listings starting at $3,499

Used Cars For Sale

2016 GMC Sierra 2500HD For Sale
6 Great Deals out of 10,560 listings starting at $28,515
2015 GMC Sierra 2500HD For Sale
11 Great Deals out of 1,051 listings starting at $27,566
2014 GMC Sierra 2500HD For Sale
7 Great Deals out of 345 listings starting at $11,990
2013 GMC Sierra 2500HD For Sale
10 Great Deals out of 555 listings starting at $14,995
2012 GMC Sierra 2500HD For Sale
344 listings starting at $12,764