'new' engine, misfire on cyl 8

[nerdwrench87]

so I got a used, low mileage motor installed, and overall runs great. however, yesterday I hosed it down because it was filthy. it started throwing a P0308 - misfire on cyl 8.

I figured it was from the water in the cylinder, as that is something I'm used to.

I heated it up nice and good and drove it around for awhile, since I don't have a compressor to blow the water out. I cleared the code, and all seemed well.

I drove it to work this morning, and going up a hill, I put my foot into it, maybe 3/4 throttle, and it starts bucking and the check engine light starts flashing. I am willing to bet it is the same code, I can pull it once I get on break.

if it is the same cylinder, could it be from water, or does it sound like the motor has something wrong with it, and I should take it back under warranty?

*note* the expy is a 2001, and the motor is from a 2004, with 82,000 miles on it. Aside from the year difference, is there a huge difference between those years? the shop also claims they did a tune up, coolant, and T-stat. anything in particular I should check out?

 

[1997SCEBFEX]

my bet would be water for sure.

the rear "T" for the rear coolant to the core back aft, if you have that, is notorious for leaking after moving things around, or not drying off properly etc. from disconnection to get to 7 & 8 plugs.

personally, these things don't like direct water/fluids on them aside from what you'd get driving.

hope you get it figured out and report back.

 

[nerdwrench87]

I just checked on break, and sure enough...P0308 is back. It is stumbling pretty good. I'm not sure about the rear T for the rear coolant... I know it has rear heating and cooling, but I have never actually used either outside of testing in the 14 years the truck has been in the family. the rear heat kind of works, but the rear a/c doesn't. I figured it was a blend door and never messed with it.

so these have another Tstat in the rear of the motor, huh? interesting!

I'll spray WD-40 and then blow it out with canned air when I get home.

 

[1955moose]

Now you know why you don't wash these motors! Your describing a shorted coil, or connection to it. A sharp on/ off bucking is electrical. Pull the connector to #8 coil, blow it out, use a smear of die electric grease, and should come back. If not swap the coil next to it, or better still if you have your old motor, grab one of those coils. In the future, wrap plastic bags around coils, and any electrical items if your going to hose down.

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[nerdwrench87]

Yeah, I guess I know that. Hopefully I didn't fry the COP. That number 8 is a PITA to get to come out to play. I lost my wigglies, so I am not looking forward to taking out the COP.

 

[nerdwrench87]

so I have not had time to pull the coil pack... I can do that on Thursday. (finals week). However, when its cold, it runs good.... until you jump on the gas. then it starts misfiring on cylinder 8.

yet it had a momentary good spell, and full throttle did not trigger the engine light, and I was doing 95 before I realized it.

sure seems to be more of a coil pack issue than a bent valve or something. and I knew better than to wash it down, my Hyundai doesn't like water either. *sigh*

 

[Bedrck47]

my bet would be water for sure.

the rear "T" for the rear coolant to the core back aft, if you have that, is notorious for leaking after moving things around, or not drying off properly etc. from disconnection to get to 7 & 8 plugs.

personally, these things don't like direct water/fluids on them aside from what you'd get driving.

hope you get it figured out and report back.

Isn't the rear "T" on the passenger side? Plugs #3 & #4
OP states P0308 That would be the back plug Drivers Side

I would check the wiring to the coil Also may be a bad boot on Plug #8

However Would agree that water and these engines don't mix

 

[1955moose]

Well if you were wondering the sex of your Suv, now you know it's a boy! Boys never like to take baths!

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[Bedrck47]

Well if you were wondering the sex of your Suv, now you know it's a boy! Boys never like to take baths!

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Is that from EXPERIENCE????

 

[docraymund]

No choice you have to pull the coil and plug out to examine and test them. If both are ok then check the electrical connectors for looseness -just slightly bend the tabs for a tighter fit.