I have a 99 yukon in it was doing a jerking motion!! So I took the codes from the computer and it said it was misfiring in the 3rd cylinder. So then I replaced the distributor cap, the plugs and the wires! That wasnt it so I chose to take it to the shop and they checked to see if there was dirty fuel injectors in the werent and the fuel filter and pump were good! the shop told me the only other thing they can think of is a sticky piston but my engine has been in great condition until this!! pLEASE HELP ME I need to figure this out
Cars & Trucks - GMC - Yukon - 1999 GMC Yukon
Answers & Comments
Do a compression test on the engine if possible, this will pick up a bad cylinder (piston or valve problem), If you have eliminated most of the ignition possibilities, I would still suspect a bad fuel injector. They need 50 P.S.I. at least to open, it could also be an electrical issue for that cylinder. Carefully check the wiring to it for being cut or pinched. If you have a small block with the fuel injectors buried under the intake plentum, Its most likely a cracked fuel line (they are plastic and get brittle over time). Even if they are getting good fuel pressure, with a crack it lowers the pressure out to the actual injector, and causes weak flow. I wouldn't suspect internal engine issues.