SPONSORED LINKS

Check engine light on and code P0306

Tiny
JVRBKA
  • MEMBER
  • 2004 CHRYSLER TOWN AND COUNTRY
  • 121,000 MILES
My wife's van has check engine light on. The code it p0306. I know it's a #6 cylinder misfire, but I can't figure out why it is misfiring.

The engine light is on. P0306. I've changed the plugs, plug wires, coil pack, and fuel injector, and the light is still coming on. I don't know where to go from here. I thought maybe fuel pressure was low and because the #6 cylinder is the last one on the fuel rail it's not getting enough pressure, but I can't figure out how to test it.

There is no scrhader valve anywhere. I've had the fuel rail out when I changed the injector and there isn't a valve on it to hook a fuel pressure gauge to. How do you check fuel pressure on these engines and is there any other ideas as to what could be causing the misfire?

Thanks!
SPONSORED LINKS
Thursday, October 4th, 2012 AT 3:35 AM

15 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Does it missfire constantly or just sometimes.
Was this
answer
helpful?
Yes
No
+3
Thursday, October 4th, 2012 AT 4:04 AM
Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
Fuel pressure can't be any different at the various cylinders. All the injectors are fed from the same large tube. I have to guess at the engine size. The 3.0L doesn't use a fuel pressure test port. You pull the supply hose off and insert a tee with a fitting.

You might consider a compression test. Chrysler typically has extremely little trouble with injectors. The spark plugs and wires normally solve 95 percent of misfires, injectors and fuel pump about one percent.
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
+1
Thursday, October 4th, 2012 AT 4:07 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Thats where I was going is compression thats why I asked if it miss fired constantly?
Was this
answer
helpful?
Yes
No
-1
Thursday, October 4th, 2012 AT 4:13 AM
Tiny
JVRBKA
  • MEMBER
  • 6 POSTS
It's a constant misfire. The engine is the 3.8l. So the next step should be to check compression?
Was this
answer
helpful?
Yes
No
Thursday, October 4th, 2012 AT 5:19 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Yes if its constant I would check the compression.
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
-1
Thursday, October 4th, 2012 AT 5:34 AM
Tiny
JVRBKA
  • MEMBER
  • 6 POSTS
If the compression of that cylinder is low, what do I do after that?
Was this
answer
helpful?
Yes
No
Thursday, October 4th, 2012 AT 10:49 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
I would check all the cylinders compression and if only the number 6 cylinder was low.I would suspect a valve issue. Then I would do a cylinder leak down test to pinpoint if that's what it is.
Was this
answer
helpful?
Yes
No
Thursday, October 4th, 2012 AT 3:05 PM
Tiny
JVRBKA
  • MEMBER
  • 6 POSTS
Ok. I'm going to try and get a compression gauge tonight.
Was this
answer
helpful?
Yes
No
-1
Thursday, October 4th, 2012 AT 3:07 PM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
They rent them at auto zone.
Was this
answer
helpful?
Yes
No
Thursday, October 4th, 2012 AT 3:51 PM
Tiny
JVRBKA
  • MEMBER
  • 6 POSTS
Finally got a compression gauge that works. The first one I got had a small hole in the hose, so I had to take it back. The #6 cylinder only had a psi of about 100. The others were around 150. I also poured about a capful of oil in the #6 plug hole and it was still reading about 100 psi.
Where do I go from here now?
Was this
answer
helpful?
Yes
No
+1
Saturday, October 6th, 2012 AT 3:54 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
I see the compression shouldnt be less then 100 psi and not vary more then 25 percent from cylinder to cylinder.I would do a cylinder leak down test next.
Was this
answer
helpful?
Yes
No
Saturday, October 6th, 2012 AT 4:35 AM
Tiny
JVRBKA
  • MEMBER
  • 6 POSTS
Ok. I'll try and get a leak down gauge in the morning. I've never done a leak down test before. Am I basically just trying to figure out where it's leaking from?
Thanks for all your help so far!
SPONSORED LINKS
Was this
answer
helpful?
Yes
No
Saturday, October 6th, 2012 AT 4:40 AM
Tiny
SATURNTECH9
  • MECHANIC
  • 30,869 POSTS
Yes you need a air compressor to supply air to the tool. You put the cylinder on tdc and see what the percentage of leakage is and where its going. The tool should have instructions.
Was this
answer
helpful?
Yes
No
Saturday, October 6th, 2012 AT 4:47 AM
Tiny
RONSTAFFORD
  • MEMBER
  • 1 POST
If you compression tested a second time with oil in the cylinder and didn't see an increase in pressure. Then you have a valve seat sealing problem and will have to have a valve job performed.
Was this
answer
helpful?
Yes
No
Wednesday, March 13th, 2013 AT 4:32 AM
Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
There's a couple of things to keep in mind. Did you have a battery charger on it while doing the compression test? If not, the last cylinder is going to read lower than the rest because the engine will be cranking slower. Also, if the engine is cold, things won't seal as well as when it's warmed up.

While 100 pounds is definitely lower than the other cylinders, that should not be low enough to cause a misfire. That cylinder will still be contributing close to the same amount of power as the others. If a valve is burned the compression will be MUCH lower. I had an old Dodge 340 on the racetrack with one quarter of an exhaust valve burned away and at higher speeds you could hardly tell. I'm probably going to be proven wrong, but I'm not convinced yet compression is the cause of the misfire.
Was this
answer
helpful?
Yes
No
+1
Wednesday, March 20th, 2013 AT 7:44 PM

Please login or register to post a reply.

Related Check Engine Light Content

Is it Safe to Drive Check Engine Light?
VIDEO
Is it Safe to Drive Check Engine Light?
Instructional repair video
Check Engine Light
GUIDE
Check Engine Light
Why is my check engine or service engine soon turned on? In this guide we talk about what this is associated with this notorious light, what it is used for and what you...
VIEW MORE

Sponsored links