Engine light on, rough idle, code P0304

Tiny
DODGESTRATUS2.4L
  • MEMBER
  • 2006 DODGE STRATUS
  • 2.4L
  • 4 CYL
  • AUTOMATIC
  • 120,000 MILES
Misfire on cylinder four. The engine light has been on for months, but I only drive the car maybe four times a week. The symptoms now are very rough idle, the engine light always on but flashes if in idle for long periods of time (more than seven minutes). Engine stops flashing when driving, but still on. Could it be EGR valve stuck open? I have changed the spark plugs. If so, where is the EGR on this model?
Monday, June 12th, 2017 AT 6:54 PM

15 Replies

Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
I have never heard of an EGR causing a misfire code. When you changed the spark plugs, did you change the coil? I would bet that the coil is failing. What you need to do is get a spark strength tester and check the sparks coming from the coil to the spark plug.

With the engine off, you will unplug cylinder four's plug wire, and connect the tester to the spark plug on one end and the wire on the other end. Start the car and observe the spark. Turn off the car, and run the test on a cylinder that is not having a misfire code, like number one. Compare the spark color and frequency. Blue sparks are stronger than yellow sparks.

This is the spark tester that I use: https://www.amazon.com/Lisle-20610-Inline-Spark-Tester/dp/B0002STSC6/ref=sr_1_3?ie=UTF8&qid=1497320343&sr=8-3&keywords=spark+tester
Was this
answer
helpful?
Yes
No
+1
Monday, June 12th, 2017 AT 7:21 PM
Tiny
DODGESTRATUS2.4L
  • MEMBER
  • 8 POSTS
Would a failing coil cause such a rough idle?
Was this
answer
helpful?
Yes
No
Monday, June 12th, 2017 AT 9:55 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Yes. It could be putting out weak sparks.
Was this
answer
helpful?
Yes
No
+1
Tuesday, June 13th, 2017 AT 7:13 AM
Tiny
DODGESTRATUS2.4L
  • MEMBER
  • 8 POSTS
I will buy a spark strength tester and let you know what happens from there.
Was this
answer
helpful?
Yes
No
Tuesday, June 13th, 2017 AT 12:15 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Okay good.
Was this
answer
helpful?
Yes
No
+2
Tuesday, June 13th, 2017 AT 5:33 PM
Tiny
DODGESTRATUS2.4L
  • MEMBER
  • 8 POSTS
The spark was yellow. So should I spend the money on a new coil pack?
Was this
answer
helpful?
Yes
No
+1
Tuesday, June 13th, 2017 AT 7:14 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Did you check another cylinder to get a base line?
Was this
answer
helpful?
Yes
No
+1
Tuesday, June 13th, 2017 AT 7:19 PM
Tiny
DODGESTRATUS2.4L
  • MEMBER
  • 8 POSTS
So all of the sparks on the cylinders were orange, but cylinder 4 was lighter. I am not sure what to do now.
Was this
answer
helpful?
Yes
No
Wednesday, June 14th, 2017 AT 9:44 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
If it was definitely lighter than the other cylinders then I think that you just need a new coil. Simple as that.
Was this
answer
helpful?
Yes
No
+1
Thursday, June 15th, 2017 AT 3:57 AM
Tiny
DODGESTRATUS2.4L
  • MEMBER
  • 8 POSTS
Replaced it. Seemed to have calmed the rough idle. I'm guessing I need to clear the code so that my engine light goes off?
Was this
answer
helpful?
Yes
No
Friday, June 16th, 2017 AT 7:18 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
You can clear it or just keep driving it. If the problem is solved then it'll go off by itself within a few days. I'm glad we got it figured out though.
Was this
answer
helpful?
Yes
No
+1
Friday, June 16th, 2017 AT 8:17 PM
Tiny
DODGESTRATUS2.4L
  • MEMBER
  • 8 POSTS
We cleared the code, but the engine light is back on with same code: P0304. Could it be fuel injector?
Was this
answer
helpful?
Yes
No
Tuesday, June 20th, 2017 AT 10:24 AM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
I'd put a tank of premium gas in it, a fuel additive (Lucas makes a good one in my experience), clear the codes again, and drive it a few days. I know it's an unconventional answer, but it's worked for me in the past
Was this
answer
helpful?
Yes
No
+1
Tuesday, June 20th, 2017 AT 11:27 AM
Tiny
DODGESTRATUS2.4L
  • MEMBER
  • 8 POSTS
Went to drive my car today, waited for cars at a stoplight for about 1 minute and a half, engine light began flashing. I haven't put a fuel additive in there, but can't imagine that would solve the problem.
Was this
answer
helpful?
Yes
No
Wednesday, June 21st, 2017 AT 4:29 PM
Tiny
HARRY P
  • MECHANIC
  • 2,292 POSTS
Flashing CEL means it set a new code. Have you scanned it yet?

Just to review, you've already done the plugs and coil so far. What plugs did you use? On a lot of cars, using plugs that aren't stock (ex. Split fire plugs) can cause more issues than they solve. Let me know.
Was this
answer
helpful?
Yes
No
Wednesday, June 21st, 2017 AT 7:29 PM

Please login or register to post a reply.

Related Engine Idle Rough Content

Rough Engine Idle
GUIDE
Rough Engine Idle
A rough en­gine idle con­di­tion is a com­mon is­sue that many dri­vers face of­ten in­di­cat­ing un­der­ly­ing prob­lems within the en­gine, fuel or ig­ni­tion sys­tem. We have cre­ated this...
VIEW MORE