Hello to all. I hope you can help me out. I have a 2005 jeep grand Cherokee with a 3.7L v6. Friday I was driving it & the check engine light come on. I pulled over to check it out. I OBD2 tested it and it said that cyl. 4 has a miss fire. So I put new spark plugs (bosch) and coil packs (deralast) in it. The jeep started but was running very roughly and blowing white/blue smoke out of the tail pipe. What does a guy do now? I would normally go straight to the distributor but this model of engine does not have one. Can you help!

 

White/blue smoke? does is smell like raw fuel or oil? Remove #4 spark plug and see what it looks like (wet/fouled?). Even if the plug was not firing at all, you shouldn't have smoke out of the tailipe. Raw fuel will look white (a lot of raw fuel) Maybe the fuel injector is faulty or stuck open and dumping fuel into the cylinder. If thats the case then #4 injector would be wet with raw fuel. If you dont suspect that the injector is bad then run a compression test.

 

Raw fuel (unburned hydrocarbons) is black, white fluffy "smoke" is usually steam from a blown head gasket, and blue smoke is oil consumption.

Do a compression test on all of the cylinders and report back with your findings.

 

Thanks for your help it was the fuel injector!

 

You evidentally have never seen a severely flooded cylinder. I have seen injectors hang wide open where the cylinder gets washed down, no ignition/fire and it produces white smoke. Now a rich running engine that still has some ability to compress and fire the mixture does indeed produce black smoke. Thats the difference in incomplete combustion and no combustion.