1999 GMC seirra misfire

Asked by Apr 12, 2016 at 02:09 PM about the 1999 GMC Sierra 1500 SL Standard Cab LB

Question type: Maintenance & Repair

I replaced my cap rotar and wires and plugs
and my truck is still misfiring but if I put it to
the floor it stops or if its just idoling

2 Answers


I'd be sure the coil pack has proper grounding...1999 tells me there is some corrosion on the connection of the Black cable to the chassis ground...and to the engine...them cables must pull 40 amps...also if nearly 10...your battery will no longer have the same potential and will not charge up very easily anymore...so battery gettin' thru is our problem....put all NEW clean stuff in there and you will be happy!~


Provided that your tune up went perfect, (and that the vehicle acted the same way before your effort) you need to locate the cylinder that has the "Misfire." Please consider that the "Misfire," could in fact be a faulty/clogged injector, as these will commonly seem like an ignition issue. Once again you need to locate that particular cylinder...then pull the plug on that one...inspect for lean or rich condition. You should be able to determine where the problem lies. Now, don't forget that you may have a cylinder which is low on compression (that's why the truck feels ok when you get to higher revs...it carries that cylinder with the momentum of the others). Could be a bent/burnt valve...and I hope not...but something to consider.

Your Answer

GMC Sierra 1500 Experts

  • #1
  • #2
    John Saffrahn
  • #3
    Glenn Clingenpeel
View All

Related Models For Sale

Used Chevrolet Silverado 1500
2,287 Great Deals out of 152,360 listings starting at $1,499
Used Ford F-150
2,603 Great Deals out of 222,391 listings starting at $1,222
Used Toyota Tundra
560 Great Deals out of 37,443 listings starting at $1,500
Used Dodge Ram 1500
349 Great Deals out of 9,682 listings starting at $800
Used Toyota Tacoma
445 Great Deals out of 41,056 listings starting at $2,600
Used Chevrolet Tahoe
646 Great Deals out of 38,080 listings starting at $995
Used GMC Yukon
397 Great Deals out of 18,725 listings starting at $1,800
Used Ford F-250 Super Duty
420 Great Deals out of 45,555 listings starting at $1,500
Used Chevrolet Camaro
267 Great Deals out of 30,511 listings starting at $4,200
Used Jeep Grand Cherokee
800 Great Deals out of 73,393 listings starting at $950

Used Cars For Sale

2018 GMC Sierra 1500 For Sale
12 Great Deals out of 30,178 listings starting at $22,990
2017 GMC Sierra 1500 For Sale
74 Great Deals out of 5,341 listings starting at $19,900
2016 GMC Sierra 1500 For Sale
83 Great Deals out of 3,159 listings starting at $13,900
2015 GMC Sierra 1500 For Sale
148 Great Deals out of 5,253 listings starting at $13,500
2014 GMC Sierra 1500 For Sale
154 Great Deals out of 3,773 listings starting at $9,995

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.