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Discussion Starter · #1 ·
The car been running fine for a year after mods until yesterday morning The service engine light came on with message "engine system malfunction blah blah blah"

AP reads the code is ECU P0300 Engine control unit DTC's.

I reset it and it was running fine all day yesterday until this morning......lights on and same code.

It feels like it will come back after the car been off for overnight and cold start in the morning.

Any idea what the problem is please?

Mods are....
AP tune
650cc injuectors
Large MAF intake
mid-pipe + exhaust
 

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I dont know the codes off the top of my head, but I had the same message appear on my car, and it was because I forgot to reset the oil interval. Its simple enough to check, just see if it claims you are due for an oil change, and if you have been ignoring it.

Jon
 

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Discussion Starter · #3 ·
I looked it up, is "random/multi cylinder misfiring"
It only happens in the morning cold start and the car will be fine if you reset it until another cold start. =(
 

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JDM R35 Premium
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fouling spark plug?
 

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Discussion Starter · #5 ·
fouling spark plug?
I honestly think it might be the problem since it was parked for a month.
So after I reset it for 3 days in a roll, this moringing the CEL didn't light up....I will just take it to POS and oil change next week and get the TSB done and see =(
 

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LiMiTLeSs
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I got the same code this morning on my way off to the dealership for the bellhousing rattle issue. I just reseted the ecu and also my car has been sitting for like 2 months since the last time I started it up and drove it around. Additionally, it has been very cold outside so I figured that may be playing a factor as well. The light didn't come on again though after I drove it around.

If its a leaky injector and I get the light more frequently I suppose its all good as I'll be swapping my injectors out to the new TSM pro series hopefully that will fix the problem if that's the case.
 

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Same issue here. P0300. Anybody get this resolved?
 

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I get the P0300 code on mine too from time to time. Now that I think about it, it typically pops up on a cold start but not always. The odd thing is the same code would pop up in similar situations when I had my TT350z. I just turn it off and go on my way. Might change out the spark plugs to see if that helps.
 

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JDM R35 Premium
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I get the P0300 code on mine too from time to time. Now that I think about it, it typically pops up on a cold start but not always. The odd thing is the same code would pop up in similar situations when I had my TT350z. I just turn it off and go on my way. Might change out the spark plugs to see if that helps.
3 things to replace

1. Spark plugs

2. Coil packs

3. Injectors (the worst case)
 

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Bumping this back up but i just got mine this afternoon after work. Seems kinda odd since i've been driving it the past 3 days, it has been sitting since January though. Are there any aftermarket coil packs to look into? Also how often do you guys change out plugs? I know i changed my plugs every oil change on my old evo since they're so cheap to buy. Mods are a Switzer p700 w/downpipes.
 

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LiMiTLeSs
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Bumping this back up but i just got mine this afternoon after work. Seems kinda odd since i've been driving it the past 3 days, it has been sitting since January though. Are there any aftermarket coil packs to look into? Also how often do you guys change out plugs? I know i changed my plugs every oil change on my old evo since they're so cheap to buy. Mods are a Switzer p700 w/downpipes.
Which plugs do u have?
 

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JDM R35 Premium
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Bumping this back up but i just got mine this afternoon after work. Seems kinda odd since i've been driving it the past 3 days, it has been sitting since January though. Are there any aftermarket coil packs to look into? Also how often do you guys change out plugs? I know i changed my plugs every oil change on my old evo since they're so cheap to buy. Mods are a Switzer p700 w/downpipes.
Okadas here with stock plugs
 

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Mine did the same thing I changed out injectors and a reflash problem solved the code would come on after start up sometimes because it would misfire and be rough to start once the injectors were changed out it would start up smooth like stock no more codes
 

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Interesting well I'm on the Switzer injectors from their p700 package. Never had any issues til Monday. Can it be because I'm still on a base tune? Haven't started data logging just yet.
 

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Bumping this back up with a update. Seems I only get this code in the morning when it's 30-35f. Got it the last 2 mornings and cleared it with the Cobb. Going to replace the plugs maybe. Anybody know the part number, gap size, and if I should be looking at any aftermarket ones?
 

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LiMiTLeSs
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Bumping this back up with a update. Seems I only get this code in the morning when it's 30-35f. Got it the last 2 mornings and cleared it with the Cobb. Going to replace the plugs maybe. Anybody know the part number, gap size, and if I should be looking at any aftermarket ones?
If you keep getting this code then you may have something up. Its either plugs, injectors, or something else. HKS makes aftermarket plugs but you should get OEM and their pregapped.
 

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P0300 is a random misfire, usually bad plugs will give you individual misfires. Random misfire while cold could be dirty mass air sensor or vacumm leak ie intake gasket etc. I would look at short/long term fuel trims while cold.
 
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