Misfire and flashing check engine light

Tiny
BADDAD56
  • MEMBER
  • 2007 DODGE MAGNUM
  • 2.7L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 100,000 MILES
My problem is I just I just left AutoZone they pull the codes up for me and it was p300 random misfire or multiple misfire. So I replaced the spark plugs had the throttle body cleaned replaced six fuel injectors, replaced camshaft sensor, replaced crankshaft, sensor. I got in car started it drove it for maybe two miles and the check engine light started flashing. What is up? I am really getting frustrated help is needed.
Saturday, June 16th, 2018 AT 12:15 AM

14 Replies

Tiny
JIS001
  • MECHANIC
  • 3,411 POSTS
You would need a more advance scanner to see which cylinders are misfiring. When one cylinder misfires, it can slow the next cylinder down on the firing order and cause a random misfire. If you can isolate which cylinder is causing the most misfires then I would suspect a bad ignition coil. If you do not have a scanner to look at live data then remove all spark plugs to see which one is wet with fuel. The one that is wet with fuel then do a compression check. Do a compression check with another cylinder with the dry spark plug. If readings are the same then the cylinder with the wet plug is most likely the one with the bad coil. Here is a link for misfire diagnosis:

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

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Saturday, June 16th, 2018 AT 1:01 AM
Tiny
BADDAD56
  • MEMBER
  • 8 POSTS
Day two decided to take it to a local shop for them to scan it when they did it came up crankshaft sensor which I replace two weeks ago. They took another look and said it could possibly be the harness they put it on the lift they said they did something with the wiring that went to the sensor. The check engine light was off and I was on my way home. And the check engine light came back on but the car was running fine now what I called the shop they told me to bring it back Monday morning.
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Saturday, June 16th, 2018 AT 6:31 PM
Tiny
JIS001
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  • 3,411 POSTS
Thank you for the update. If it is the same code then they may need to do crank and cam relearn if the feature is available or the crank sensor may be defective. Please let us know what fault codes came back when they recheck it Monday.
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Saturday, June 16th, 2018 AT 6:54 PM
Tiny
BADDAD56
  • MEMBER
  • 8 POSTS
Okay day three car's check engine light. Well as all of you know been having some problems what this check engine light of mine. So far six new fuel injectors, one gas cap, one set of plugs, one camshaft sensor, and one crankshaft sensor. Well today the code came up po172 which is oxygen sensor in bank one. So I believe that would be the upper so I guess that is next. I also replaced the serpentine belt I noticed it was slightly worn. I hope replacing the oxygen sensor will resolve this problem once and for all. Do you think I should replace both of them or just the one thanks again? Your buddy
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Monday, June 18th, 2018 AT 9:16 PM
Tiny
JIS001
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  • 3,411 POSTS
P0172 is for system running too rich. You would need to check both banks to see if both are running rich. Looking at long term fuel trims bank one will most likely be -25% or higher.

If bank two shows the same readings then I would focus on the mass air flow sensor. Also, they should look at the freeze frame data to see if the codes are set at idle or cruising to try and duplicate the concern. Get back to us on what fuel trims are at on both banks, both long and short term fuel trims to better guide you before you replace the oxygen sensor. Also, what were the trims on freeze frame and if rpm shows idle or cruising speed?
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Monday, June 18th, 2018 AT 11:04 PM
Tiny
BADDAD56
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Here is what I have so far:
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Tuesday, June 19th, 2018 AT 1:40 AM
Tiny
JIS001
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Both banks are running rich. Can you post what the freeze frame is? Would need to see RPM and short and long term trims.
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Tuesday, June 19th, 2018 AT 12:57 PM
Tiny
BADDAD56
  • MEMBER
  • 8 POSTS
Magnum no check engine light on replaced upper and lower oxygen sensors along with the serpentine belt and I am rolling no lights, no misfires. Thanks guys for everything.
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Tuesday, June 19th, 2018 AT 10:48 PM
Tiny
BADDAD56
  • MEMBER
  • 8 POSTS
Well, just when you thought you were going to have a fantastic day. Yeah, hop in your car start that baby up and you are ready to go! Wrong check engine light came back on. This is really starting to frustrate the heck out of me. I have got to go pull the codes.
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Wednesday, June 20th, 2018 AT 12:39 PM
Tiny
JIS001
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If it is the same codes then please post the freeze frame data as well.
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Wednesday, June 20th, 2018 AT 12:55 PM
Tiny
BADDAD56
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I think I am giving up.
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Thursday, June 21st, 2018 AT 12:36 AM
Tiny
JIS001
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Sorry to hear you are getting frustrated? Did the same codes for fuel trims return?
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Thursday, June 21st, 2018 AT 8:05 AM
Tiny
BADDAD56
  • MEMBER
  • 8 POSTS
Hey guys, it is Magnum 2007 2.7, back to my check engine light problem. It is still there let's see where did we leave off I believe it was codes p0175 and p0172 well that is where we are at. Took it to my local Pep Boys and wanted to get it diagnostic check there after them having it for twelve hours they said they could not find nothing the matter with it. I honestly believe they did not even look at it.
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Monday, July 23rd, 2018 AT 7:32 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 50,480 POSTS
These fuel trim issue can be caused by a MAP sensor that needs to be replaced. The problem is when this sensor gets off a little it will affect the engine management without triggering a check engine light. here are diagrams to help you replace the sensor.

This guide can help as well.

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

Check out the diagrams (below). Please let us know what happens.

Cheers, Ken
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Friday, July 27th, 2018 AT 11:19 AM

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