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Engine misfire? I've been getting the P0301 code?

Tiny
STUCKINRENO
  • MEMBER
  • 2003 DODGE CARAVAN
80,900 miles. I've been getting the P0301 code on and off for the last two months. Firestone replaced plugs, wires, coil, and injector and also ran fuel system cleaner through it (total $900) and purred like a kitten for two weeks and then the code came back. They deferred me to Dodge dealer saying it's probably a burnt valve and they didn't want to get into that. Dodge ran their own fuel system cleaner and de-carbonization ($390) through and got nothing. They then replaced the valve ($1600! Which they said was burnt but wouldn't show me) and it still misfires. Compression comes back within normal range. Now they want to "test" to see if ECM is the problem. If not ECM, they want to pull the tranny and inspect the flex plate. They think its creating enough of a vibration that it is causing the misfire. What have they not considered or tried? They want $300 to diagnose the ECM and $600-$700 to pull and put back the tranny. The Dodge dealer told me they swapped/changed plugs and wires around to make sure they weren't missing anything there. They also ran a jumper wire from the molex plug on the ECM straight to the #1 injector to make sure it wasn't a wiring issue.
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Friday, October 9th, 2009 AT 4:53 PM

76 Replies

Tiny
CH112063
  • MECHANIC
  • 1,320 POSTS
So plug, wire, injector, valves, compression, all good. So the engine runs good, the check engine light stays on and it makes a metal sound and vibration. What engine? And the dealer must have monitored the engine with their DRBIII and saw that the engine was ok and the fuel pressure was ok. What they did was what anyone would have, there is only the computer and the noise. I hope a flex plate causes this.
Vigration yes, possible crank sensor problems, maybe. Hope it is ok. You have a great van but stay with a good dealer, the firestone uses cheaper parts and cheaper labor. Then send you to dealer. It'll all be ok. Anything I could help with I'll try.

This guide can help us fix it

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Joe
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Saturday, October 10th, 2009 AT 1:09 AM
Tiny
STUCKINRENO
  • MEMBER
  • 5 POSTS
After all the repairs, engine still misfires and check engine light comes and goes with no consistency. Dodge dealer sees the misfire on their computer when monitoring it. Only vibration comes from the misfire and no additional noise other than the obvious sound of a misfiring engine. Engine is 3.8 v6. Great vehicle. This is the first major work beyond steering rack replacement years ago.
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Saturday, October 10th, 2009 AT 5:07 PM
Tiny
CH112063
  • MECHANIC
  • 1,320 POSTS
3.8L misfire in number one cylinder. The latest repair was a flex plate, a PCM, and it was returned to you with this problem(dead miss) still present? Is that where you are at now? Joe I'll check back at 11.
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Saturday, October 10th, 2009 AT 7:26 PM
Tiny
CH112063
  • MECHANIC
  • 1,320 POSTS
You only put let's see 2000.00 at dealer and another 1000.00 at Firestone. You have a good van with all services and parts your gonna need someday anyway. Don't drive it too much on 7. Later I'll tell you how to proceed. If you ask me. OK Check later, ok Don't worry, it will be fixed and its good all the expensive parts were replaced.
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Sunday, October 11th, 2009 AT 4:02 PM
Tiny
STUCKINRENO
  • MEMBER
  • 5 POSTS
PCM and Flex plate are what dealer wants to do next-haven't done it yet because I don't know if it's the right thing to do next. I am hoping there is something the mechanics have overlooked that won't cost me another grand.
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Sunday, October 11th, 2009 AT 8:32 PM
Tiny
CH112063
  • MECHANIC
  • 1,320 POSTS
I get it. If they swapped out the Injector(not spark plug) it may be the PCM, but you mentioned plug, not injector. Did you have this dead miss when you were just driving along, or did it occur after any one incident? And why is the plate being looked at? Also who replaced coil pack?
You understand that These two items(coil pack, injector) if swapped leave only the PCM or a very unusual wiring problem. Why don't you find transportation, or have them replace the PCM, and hold on the engine repair to see how it runs, if it still has a miss, from the cylinder, then leave it with them til the engine has 6 cylinders and wait on the flex plate. Ok Joe
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Sunday, October 11th, 2009 AT 9:58 PM
Tiny
STUCKINRENO
  • MEMBER
  • 5 POSTS
Firestone was the first to completely replace plug, wires, and injector. Dodge switched out all three to make sure they weren't bad. Dodge also replaced coil. They think flex plate is bad and is causing the misfire. They used a scope camera to do a visual inspection of the flex plate but couldn't see anything and want to pull tranny to see for sure. But. They want to run tests on PCM first which will cost me $300 and for that price, I can get a rebuilt one and switch it out myself which I'm thinking of doing.
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Monday, October 12th, 2009 AT 11:22 PM
Tiny
CH112063
  • MECHANIC
  • 1,320 POSTS
Good idea. Where from? Dealer or parts store? That's a damn good idea. Unless you could find one on someone elses caravan.
Good luck. I was talking to a friend about this problem, it is a very unusual problem but we both would try a PCM first. I don't understand, the flex plate but I'm sure it must have something to do with the trigger for number one, did anyone pull yhe plug wire to make sure that it is a no spark AND a no injector? I guess so.
I agree, It controls both. And you will have a spare just in case. Well I hope it gets going for you. I want you on the road again ok. Joe
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Tuesday, October 13th, 2009 AT 9:04 PM
Tiny
STUCKINRENO
  • MEMBER
  • 5 POSTS
I ordered the PCM from a salvage yard in Louisiana-gave them the numbers off of my PCM so they can match it up but it was no help. Then I have a different shop look at it and they changes the MAP sensor all fixed ! Man that was an expensive run around.
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Tuesday, October 13th, 2009 AT 11:42 PM
Tiny
CH112063
  • MECHANIC
  • 1,320 POSTS
Glad you could get it fixed, that kind of problem can be tough. Please use 2CarPros anytime we are here to help

Cheers
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Thursday, October 15th, 2009 AT 12:34 AM
Tiny
DENNIS MORGAN
  • MEMBER
  • 1 POST
2003 Dodge grand caravan. Bought it last week, ran great in test drive. One owner. After I got it home it started mis firing. Shakes the engine really hard. I have replaced or repaired the following which have not worked. Any advice would be greatly apprecitated.
Dropped gas tank, cleaned it out, new filters, check gas pressure.
New plugs, new plug wires
new coil pack
new injectors
new wiring harness on it
map sensor
replace PCM (GOT THIS FROM JUNK YARD)
What else is there to do?
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Tuesday, October 3rd, 2017 AT 10:45 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Lets start at the beginning. Can you do a compression test to all cylinders please? If you don't have a gauge the auto parts store will rent you one for free, here is a guide.

https://www.2carpros.com/articles/how-to-test-engine-compression

Please let us know what happens and upload pictures or videos of the problem.

Cheers, Ken

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Wednesday, October 4th, 2017 AT 1:52 PM
Tiny
GOLFGUY54
  • MEMBER
  • 2 POSTS
  • 2003 DODGE CARAVAN
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 90,400 MILES
I have a KOER P0302 misfire code. Did not happen until I had plugs and wires replaced (bad move). New coil pack also replaced. Injectors cleaned when plugs and wires replaced. Mechanic can find nothing to cause misfire. Takes about 1 week for Check Engine light to come on after being reset.
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Monday, July 27th, 2020 AT 9:41 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Hi golfguy54, Welcome to 2carpros and TY for the donation

Cyl no.2 misfire-check the sparkplug/compression and injector for this cylinder-then report back-try erasing the code again
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Monday, July 27th, 2020 AT 9:41 AM (Merged)
Tiny
GOLFGUY54
  • MEMBER
  • 2 POSTS
I have not had a chance to do a compression check but what I did notice that makes no sense is that when A/C is on the misfre/stumble at idle disappears.

I was also going to switch the plug with another one and try another wire on that cylinder to see if it makes any difference.
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Monday, July 27th, 2020 AT 9:41 AM (Merged)
Tiny
CMIKE101
  • MEMBER
  • 1 POST
  • 2003 DODGE CARAVAN
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 80,000 MILES
2003 Dodge caravan. The engine start's to stumble just as you take off, it will back fire ever so often when you hammer it at highway speed. I checked the plugs and wire's, I cant find a vaccum leak. Is there anything else I can check? Thanks for any reply. And the check engine lite is on.
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Monday, July 27th, 2020 AT 9:41 AM (Merged)
Tiny
PFK21961
  • MEMBER
  • 1 POST
  • 2003 DODGE CARAVAN
  • 3.3L
  • 6 CYL
  • 2WD
  • 176,000 MILES
Engine is missing at idle and then missing very bad when trying to give it gas. I put new tank filter new wires new plugs. When going down the road it is missing bad. I am thinking its the timing sensor. I have checked at night under the hood no sparks anywhere. What are you thinking? Timing belt or chain is fine. Still thinking is that sensor. What are your thoughts?
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Monday, July 27th, 2020 AT 9:42 AM (Merged)
Tiny
STEVE W.
  • MECHANIC
  • 13,576 POSTS
Timing is not adjustable on that engine. It sounds like multiple misfires. You need to get a scan tool on it and watch the misfire counters for each cylinder. That will narrow it down fast.
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Monday, July 27th, 2020 AT 9:42 AM (Merged)
Tiny
RON1928
  • MEMBER
  • 1 POST
  • 2002 DODGE CARAVAN
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 51,000 MILES
Can some please tell me what I can do to fix the cylinder 3 misfire
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Monday, July 27th, 2020 AT 9:42 AM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
A misfire in a specific cylinder should lead you to check the spark plug, fuel injector and compression start with this. If its a no-go check also below

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel
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Monday, July 27th, 2020 AT 9:42 AM (Merged)

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