2009 VW Routan AKA Chrysler minivan with 3.8L v6. 113K miles
Couple weeks ago code P0303 popped up so I replaced the plugs and wires. I used the Champion double platinum that came stock on this engine. The light went away and we've been driving it with no issues.

This morning my wife says it did a "rough start" and it popped the same code again with the light on. Van is running great otherwise.

What else can I check?

Thanks.

Is that code for #3 cylinder? If you can't duplicate the problem enough to accurately diagnose it, then you might just have to throw parts at it until you hit the right one. With no other codes, I would try a coil pack and then swap the injector. You should do a compression check, but if the problem is intermittent, that doesn't seem likely.

What does that plug look like now?

My mother has a 2005 3.3 T&C.

I have had problems three times with new RE14PLP5 Champion double platinums quickly going bad by losing the welded-on tiny platinum discs.

I finally did away with using the OEM plugs with
NGK LZTR5AIX-13/2314 Iridium plugs
and the problems went away.

On the 2005 there was also a TSB indicating that some OEM coil packs were bad.

I tried troubleshooting the spark problems with a KAL Equip ignition analyzer

http://www.ebay.com/itm/Kal-Equip-Spark-...739&vxp=mtr

that clips on a wire and gives you
peak KV,
average KV and
spark burn time,
but found that with the 3.3/3.8 "wasted spark" two cylinder firing coil packs, you had to disconnect the wire to the other cylinder and connect it instead to a known good sparkplug simulator

http://www.ebay.com/itm/Adjustable-High-Energy-Ignition-Spark-Plug-Tester-Pick-Up-Coil-Diagnostic-Tool-/231314358857?epid=1326254621&hash=item35db690249:g:14MAAOSwxH1T-AoA

When I had similar symptoms with my Mazda, it turned out to be bad injector seals. I replaced a bunch of unnecessary parts before I broke down and took it to the dealer. The codes it was throwing was for misfire on #5, and random misfire. I was thinking I had a spark issue, and ignored the distinct smell of gas under the hood...

All the plugs looked to be the same condition when I pulled them. It is the code for cylinder 3.

The check engine light turned off again.

I haven't had time to dig into it yet, but I'll check the coil pack then check for vacuum leaks. If the intake gasket is leaking, it could cause a misfire, right?

I'll report back when I have more time to dig into it.

Thanks for the replies.

Had a misfire code on my PT that drove me crazy. Finally found out it was a burnt valve.