P0420 P0300

paulmj

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#1
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MAKE: Dodge
MODEL: Dakota
YEAR: 2006
MILES: 134000
ENGINE: 3.7L
DESCRIBE ISSUE....Have been trying to solve misfire problem. It is an intermittent problem but when it does occur the check engine light sometimes does flash and idles rough with hesitation. Used my scanner and have noted that misfires only show up on cylinders 2, 4, and 6 with greatest number at cylinder 6. Cylinders 1, 3, 5 will show less than 5 misfires and 2, 4, 6 will show thousands. Sometimes there will be next to no misfires all cylinders.
Freeze frame data for P0300: fuel system 1 status: cl, fuel system 2 status cl, calculated load value 44.3%. coolant temp 162 Celsius, short term fuel trim bank 1 -9.4%, long term fuel trim bank 1 9.4%, short term fuel trim bank 2 -32.8%. long term fuel trim bank 2 7.0%, intake manifold absolute pressure 6.7 kpa, engine rpm 187 rpm, vehicle speed sensor 0 km/h, ignition timing advance for #1 cylinder 12.5, intake air temp 118 Celsius, absolute throttle position 13.7%, fuel level input 27.8%, barometric pressure 14.5 kpa, control module voltage 14.2 v, absolute load value 32.5%, commande equivalence ratio .999, relative throttle position 0%, ambient air temp 91 Celsius.
New plugs and all COP's; checked fuel pressure which was 58 to 60 and did not change when truck was running or rpm's increased; checked compression in cylinder 6 yesterday and 180 psi; checked around intake with carb cleaner and rpm's did not increase.
Cylinders 2, 4, 6 show misfires with on board monitor test using my scanner and P0420 is for bank 1 cat. P0420 always presents itself first since I have been checking and erasing codes recent month.
Any help is appreciated.
 

kev2

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#2
you only have the one converter?
Seams the system bank 2 -32.8. would be issue
Do you ever get codes in the P020x series?
Do you ever get P035x series?
Anything special in freeze frame?

Check Bank 2 (12v) feed to injectors and coils*, A noid light when issue happens would confirm...

*I show a common red wire, spliced alot.
 

paulmj

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I'm not sure what question is regarding one converter. I have never gotten codes in P020 or P035 series. The information in initial post is freeze frame data for P0300. I will check 12v feed to injectors and coils. I will check on noid light. Misfire never seems to happen when engine is cold or on initial trip for day. Thank you for your help.
 

paulmj

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#4
Sorry, I misunderstood converter question I don't know what I was thinking. No, I have 2 catalytic converters. Bank 2 are the misfire cylinders of 2, 4, 6 and bank 1 is the converter code (P0420) which also confused me.
 

kev2

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#5
It was a question - the vehicle only has the one converter. Double checking without looking it up myself.
THe problem is intermittent - and when hot. correct?

I am thinking something is causing bank 2 cylinders to misfire, intermittent SO I suspect ignition or injectors - the wiring diagram showed a common source of 12v to injectors and coils. With the noid - try to shake tug wiggle the harness.

Another thought - maybe do a fuel pressure test then leaving KOEO observe pressure drop - drops Xpsi in 5min.
 

paulmj

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#6
The problem is intermittent and when hot--yes. I do not have a noid but I am looking into it. I can also try KOEO for fuel pressure...would drop in fuel pressure only cause misfires on 2, 4 , and 6? Thanks
 

kev2

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#7
I am thinking of possibilities - I like easy things first.
And I am thinking electrical a harness chaffed and open or grounded - Why I said tug, pull wiggle harness, see if condition appears.
 

kev2

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#8
I reread your data post 1 - bank 2 fuel STFT It is - neg 32.8 ? or is that a dash for clarity?
 

paulmj

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Yes it was negative 32.8 in that p0300 freeze frame


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billr

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#10
That's a big wad of data to wade through, but several entries seem so bogus it is all suspicious to me. Note these:

ECT = 162C That seems impossible, it is equivalent to 324F
IAT = 118C Same there, it would be 244F for under-hood temp
rpm =187 That's too low to be even remotely reasonable
MAP = 6.7 kPa Maybe possible in extreme "overrun", that is nearly 28" Hg vacuum if I did my math right
Barometric pressure = 14.5 kPa That one is simply impossible, no place on Earth has ever had a baro even nearly that low
 

paulmj

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#11
I was wondering about the ambient temperature and rpm when I saw it but I read it directly off my scanner today and included it all so it may be helpful. I can clear codes again and get new frame of data this week. Why would this happen


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nickb2

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#12
Agree with Billr, the readings he quoted are next to impossible or they were typos, or that freeze frame caught quite a glitch.

We cannot work with those numbers to help you with this random misfire and cat efficiency code. Can't wait to see another freeze frame and see if readings are more adequate to a real world scenario.
 

paulmj

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#13
They were not typos...I took my time so I could be accurate. I'll clear codes again tomorrow and post later in the week. Thanks for your time attempting to help today.


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