2002 Ford Explorer Misfire and multiple codes
 

A couple worker of mine has an 02 explorer with the 4.0. he recently had the intake manifold gasket replaced as it had a pretty big intake manifold leak. He then ran through emissions and passed.

Yesterday, his check gauges light came on and the engine was shaking pretty violently. I couldn't do anything for him as he lives on the opposite side of the valley from me. So I brought one of my code readers into work and on break, we read them. There are 6:

PO171
PO174
PO300
PO304
PO305
PO316

The only thing he did yesterday after work was drive home and took it to a car wash. Not sure if maybe water got into one or a couple of the boots for the coils. Seems unlikely though. I've only ever seen an issue with washing a car on distributor engines.

Anybody have any ideas where to start? 2 of the codes are specific cylinder misfire codes, the others are random cylinder misfire and misfire on startup. I am doubting that the multiple coils just failed at the same time.

171 and 174 are lean codes on BOTH banks... normally that means vacuum leak on a hose common to both sides, or intake gasket leaking.......

300 and 316 are random misfire codes..... 304 and 305 are misfire on #4 and #5 cylinders.. I don't think you have multiple coils, I think you have one coil ( or 2) for all 6 cylinders.. Could be one coil or could be crank position sensor, etc. Hard to tell from here, but coil could be a good bet.... Maybe water got in an electrical plug / power to the coil ?

I'm also leaning toward the vacuum leak as it could explain all 6 codes. In addition to the intake manifold gaskets as a common issue, I'll also mention the PCV elbow as another common source for a vacuum leak common to both cylinder banks.

-Rod