CEL - P0304 troubleshooting? 2005 MSM
 

I posted this 31 hours ago on the MSM board. Of course there are no replies. I figure I'll get a few hits on here before I get home in the morning:


We are getting ready to take a little weekend vacation and haven't driven the MSM since Deals Gap (July). I fired it up today and it threw a P0304 (misfire on cyl#4). I am not around the car right now (haven't hardly been under the hood so I cannot remember what the COPs look like and how the wiring is) but my thoughts are to swap COPs (not sure which cyl# to swap it with) and see if I throw a code. If the code follows the COP I know it is a bad COP. If it doesn't then it might be the spark plug. Does this sound right? What else should I look at? Thanks!

Try switching out COP #4 with Cop #3 and see if it follows it. #4 is the one at the back next to the firewall.

I believe a bad tank of gas can cause this. And .........I know that this will sound stupid. Unscrew your gas cap, and then screw it back in. Make sure that the gas cap is not loose.

I think the gas cap thing causes an EVAP code which is separate. A misfire in cylinder 4 is caused usually by ignition related components. Not knowing what you have done, I can't further stipulate. However, a cracked boot on your COP could cause this, as could a faulty plug, or a injector problem or vacuum leak in the area of the cyl4 runner could do such as well. A spark plug is cheap, soo... when you are switching coils around, switch it out. How many miles are on your current plugs?

Well, my wife must have a horseshoe up her ass. As I said, we are two days away from leaving town and the car wouldn't run. I swapped the coils and the code did not follow the swap. Then I swapped spark plug #1 and #4 and the code followed the swap. I can't see anything wrong with the plug but there must be a defect in it. Put in a set of NGK BKR5E-11 plugs (the best I could do on short notice) and the car runs fine.

Really? The parts store didn't stock 6's. Fail on their part. The only ones i have trouble with are the 7's

Yeah, I can live with them. If I start having problems I'll change them out.
$10 for an emergency fix isn't too bad!

The good news is that I picked up a Squier Mini at the pawn shop today (a rare one with a speaker <G>):



http://www.lightweightmiata.com/misc/squiermini.JPG

So, 3.5 years and 700 miles later (I know, I really need to be driving the car more) I decided to drive the car to Walmart. I pull the car off the lift where it normally lives and the engine is missing like crazy. I put it back in the garage and drive the Geo to Walmart instead. A few days later (today) I read the codes. P0304 again. I'm going nuts at this point because I know I'm in for at least a new coil pack, at worst .... who knows. I pop the hood and get ready to pull the coils and run a compression check. What do I find? The #1 plug wire on the #4 coil is pulled off. Not loose - completely off. I have no idea why it is like that but I am one happy camper at this point (and my wife still has a horseshoe up her ass). I wish my auto tranny problem (some of you may have read my post about my V8 Miata tranny slipping) will be this easy to fix. I somehow doubt it will though.