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CEL & P0300 Code

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Old Nov 5, 2015 | 04:07 PM
  #1  
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Default CEL & P0300 Code

Short story, went on a spirited drive the last few miles before home. Everything was normal, no issues at all. I parked in the garage and was letting the car idle for a few minutes while i unfolded my car cover. I got back in and noticed i had a solid CEL (was not flashing), so i shut the car off and pulled up the codes and it displayed:

10-PCM P0300 H C

From what i understand that is a misfire code. I cleared the code and let the car sit for awhile. I fired it back up and everything seemed normal. Any idea what this is about? Some general searching on google shows a lot of people have trouble with the ignition compenents but i have no negative symptoms at all.


Car has 40k miles, normal bolt on's, and a Texas Speed 228R cam. Still has the stock heads but i was told the car was tuned and i've never had an issue with it in the 5k miles i've owned it.
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Old Nov 6, 2015 | 06:50 AM
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Clear your code and see if it comes back. If it does I can post the diagnostics on it.


Mr. Sam
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Old Nov 6, 2015 | 07:47 AM
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Have you had a crank position sensor relearn performed after cam replacement? A lot of people say it's not necessary but believe me, it is. I found out the hard way. Check the usual culprits such as spark plugs, wires and coils. If all checks out, you may need a CKP relearn.
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Old Nov 6, 2015 | 10:39 AM
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How does the car idle? May simply be due to a rough idle. I presume the coolant temp got a bit warmer than usual from those "spirited drive" miles before home. May just need to have a bit more idle air programmed into the tune at higher coolant temps.
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Old Nov 6, 2015 | 10:55 AM
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Originally Posted by Brad055
Short story, went on a spirited drive the last few miles before home. Everything was normal, no issues at all. I parked in the garage and was letting the car idle for a few minutes while i unfolded my car cover. I got back in and noticed i had a solid CEL (was not flashing), so i shut the car off and pulled up the codes and it displayed:

10-PCM P0300 H C

From what i understand that is a misfire code. I cleared the code and let the car sit for awhile. I fired it back up and everything seemed normal. Any idea what this is about? Some general searching on google shows a lot of people have trouble with the ignition compenents but i have no negative symptoms at all.

For what it's worth... PULL the CODES BEFORE you shut it OFF next time


Car has 40k miles, normal bolt on's, and a Texas Speed 228R cam. Still has the stock heads but i was told the car was tuned and i've never had an issue with it in the 5k miles i've owned it.
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Old Nov 6, 2015 | 11:25 PM
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Old Nov 13, 2015 | 02:05 PM
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Little update: I've sense started the car and let it idle up to temp and it sounds and runs just as it always had. Unfortunately i bought the car with the cam, so i have no idea if any tuning has been done to it. I was told it was tuned by a shop in Kansas but i do not have any proof other then word from the previous owner (which i trust). After letting the car idle up and rev'ing it a few times the code did not reappear. I did not have time to take it for a drive, hopefully this weekend.
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Old Nov 18, 2015 | 11:20 PM
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There are certain mods that create "false misfires"--- On an automatic car a stall converter is known for creating false misfires----On an automatic or manual trans a cam can also create a false misfire--- Most tuners know this and can massage the misfire tables in your tune so the false code does not re-appear----
ALSO on an automatic trans-----A misfire whether real or false will make the TQ converter UNLOCK--- so you will get a constant locking and un locking of the converter which eventually will overheat your trans and lead to a failure !!!!!
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