Repeated Coil Failures in '02 - caused by oil leak?

[Tiberius]

Hello all.

 

I have a 2002 Pathfinder with a 5 speed and about 200k miles. It's now had multiple coil failures. For a while my mechanic was replacing one at a time, and finally decided that there was a bad batch of coils and replaced all coils (with a different brand) and all new plugs as well.

 

The problem recurred (misfiring and blinking CEL).  The time interval between failures was about the same as before switching brands (probably 500-1000 miles or less).

 

This rig also seems to think its a two stroke - when you add gas, you also add a quart of oil (tho not in the fuel tank). At times it visibly smokes a bit at shutdown.   It seems to be leaking oil from the valve covers.  The visible smoke can be a bit troubling.

 

My admittedly uniformed hunch is that the oil leak is messing up the coils and/or plugs.  My mechanic said they saw no sign of that, but plainly something is causing the coil failures.

 

Thanks for any insights anyone can offer!

[Slartibartfast]

I'm not sure what would cause that other than junk parts, assuming the plugs and boots are OK and the plug wells aren't full of oil. I'm assuming the mechanic swapped them around to confirm that the coil pack was the problem, and it wasn't the same cylinder each time. Were the old plugs oil-fouled/unusually worn/tested bad, or were they replaced as a "while we're in here?"

 

I'd be surprised the valve covers leaked enough to lose that much oil. There's an oil cooler that also tends to leak. Unfortunately the early VQs also tend to burn oil. My dad's '03 burned a quart/1k miles. Ran fine, but smoked out the parking lot on a warm start. (We suspected valve stem seals, but never tore it down to find out.) I don't remember it having coil issues, though.

 

Looks like you can still get OE coils from Nissan. They ain't cheap, though.