Error Code P0304 Cylinder 4 Misfire Detected

[WV05Cruiser]

My check engine light has been coming on and going off for the last couple of weeks. When I pulled the code, I got P0304 Cylinder 4 Misfire Detected. The car has a rough idle when at a stop light, but other than that it runs fine.

I installed Chapion Platinum plugs and Mopar Performance Plug Wires 7,000 miles ago and gapped the plugs at 0.040.

Could it be that I may have a coil starting to go bad?
Has anybody seen this problem??

Also, what should the torque be for reinstalling the intake bolts???

Thanks!

[quicksilverdon]

Not many coils go bad, and when they do, it takes out 2 plugs...
Get some starting fluid and spray along intake manifold seam - if idle smooths out, you have an intake gasket problem.
I'd also swap wires 1 to 4 and see if anything changes - I think you can swap 1 & 4 without having to take intake off..

[66CUDA]

Yeah, the 'ole P0304 code...had it pop on my wife's previous car, 2004 Hyundai Accent....We drove it for over 30K with it lit...turned out to be an air leak from the intake side on the #4 cylinder. MPG's never suffered...avg 33mpg with auto.trans. I cranked down and tightened the intake bolt and it stayed off for about 200 miles but came back on. Its a 4 hour job on that motor because you have to depressurize the fuel rail which is above the intake. We ended up selling the car with it still lit. Car acted the same as yours...rough idle @ stop but drove like a top! Maybe you didn't follow the proper intake bolt pattern and proper torque ft. lbs. on the bolts after you did your plug & wire change. That would cause a vacuum leak. The intake bolts require 13ft. lbs of torque and the tightening pattern is on the sticky post for the spark plug change. Geez, I miss that Hyundai...car ran great.

Good Luck, 66CUDA

[WV05Cruiser]

Thanks for the ideas! I plan on working on the car this weekend, so I will keep you posted.

The vaccum leak seems a little wierd, since it has been a year since I changed the plugs and the best I can remember, I did tighten the intake bolts from the center out... I think!

I had already ordered a scremin' demon coil before my post, so I am going to install it, check all the wires, regap the plugs and make sure that I torque in intake bolts in the right order.

The funny thing is that the check engine light has now went OFF.
Go figure.

Thanks again!

[Hooligan]

Just think, the threat of a "Scremin' Demon" coil fixed the code!!!

[66CUDA]

My CEL on my Accent went off and on for the first six months, sometimes staying off for a few days. Then it progressed where it would flash during warmup and stay lit after I drove it a few minutes...

Good Luck, 66CUDA

[dsmturbo]

I just got this same code today, and I haven't messed with anything. So, it could be a leaking intake gasket?

I was going to change the plugs and wires, as the wires look original (82K) on car.

Which cylinder is which, starting from left to right when looking at engine?

[Hooligan]

#1 is at the left, looking at the engine. #1 & 4 take the short wires, #2 & 3 use the long ones.

[CREWZIN]

I believe #2 and #3 take the short wires.

[dsmturbo]

Much appreciated guide, thank you

So, I decided to replace plugs/wires, I started at far left, on the turbo it appears I can change all without pulling intake. Well, it took me 2 hours to replace that plug and wire!!! reason, I could not get the wire off, until I grabbed a really long pair of needle nose pliers and used a piece of 2X4 as a safety so as not to damage anything on engine, and twisted and pulled for 45 minutes. It finally let loose.

I am sure these are original plugs/wires with 82 Kilo on them.

I had enough and went for a relaxation journey for rest of day.