Notorious p300 help

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The misfiring gang

Greenie N00B Member
Hey guys so long post here.. but I need help.

I bought a 2008 speed 3 back in March which had a misfire, didn’t think it would cause me as much trouble as it has but I don’t know what else to do.

i have changed so much an tested so much. Such as the spark plugs (ngk 7 gapped at .028), 2 sets of coil packs, 2 sets of cleaned an tested injectors with new oem seals upon install, got the valves cleaned, replaced pcm, replaced engine harness ( was getting p202 an p203 codes before replacing), hpfp, crank shaft sensor, cam shaft sensors, pcv valve, intank fuel pump an regulator, fuel pressure sensor, spill valve, cleaned an new gaskets on egr, boost solenoid, complete timing kit with new oil pump, all new relays an most fuses, tested purge valve an vvt solenoid, replaced every gasket besides head an exhaust gasket, check the turbo all seemed okay, sent it to mazda an they said injectors or clogged cat so I replaced the injectors again an installed catless dp. With no change. Compression test 195 each cylinder an leak down test passed with less then 15% leakage. Car only has a the catless dp an sri upgrades an I haven’t got a tune YET (I know I need one by read on an you’ll understand) cuz I’m just troubleshooting.. from when I bought the car till now nothing has changed.. When I’m driving normal the car does not misfire. Has a baby misfire at idle. It misfires on hard loads such has more then 25% throttle or over 2-3lbs of boost. Anything under that no issues at all. Which is why I haven’t got it tuned yet cuz I couldn’t WOT it even if I wanted to. But the tune is coming soon. But even before the catless Dp it was doing the same thing so. I’m no newby to any of this. I’m just lost at this point.

Any help or insight would be much appreciated before this thing goes up parts.
 
What brand and size of SRI do you have? Without a tune, your ECM might have problems making the proper calculations. The first action in a tune is to calibrate your intake before doing WOTs. The dp could potentially be an issue down the road without proper mods/tuning...You dont mention upgraded hpfp internals which are 101% required.
 
You have done about everything I would. Now are you using OEM coilpacks? If using that yellow crap, that is your problem. Also, injector seals should be upgraded too. OEM sucks. What HPFP upgrade? Can you do some logging and post them? idle, etc.
 
Raider said:
You have done about everything I would. Now are you using OEM coilpacks? If using that yellow crap, that is your problem. Also, injector seals should be upgraded too. OEM sucks. What HPFP upgrade? Can you do some logging and post them? idle, etc.
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i haven’t done the upgraded internals yet cuz I’ve been trying figure out this misfire. Once I got it I was gonna baby it until I could get the tune and internals. An I’ve been using the v2 accessport an the thing it kinda wonky tbh. An coil packs are oem.
 
I have seen bad HPFP internals cause random misfire. Grab some Corksport and upgrade. If it continues, do some logging and upload the log file.
 
Raider said:
I have seen bad HPFP internals cause random misfire. Grab some Corksport and upgrade. If it continues, do some logging and upload the log file.
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The hpfp on the car rn is off my friends 2012 speed 3 an he has mine. His car runs just fine with my old one and my car still misfires with his.
 
A worn cam lobe or a bad lifter can cause a misfire but have no noticable leak down. You'd still show good compression as well.
 
I didn't read if you have a AP, so do you have one and logs? Once you post some with correct logging parameters. Look on forum for more. The list of work done is great. Logs though are like Candy to a kid here. Lot more interactive help once others look at logs. No AP?. Spent just enough for a compatible cable and Download free VersaTune version to log stuff..
 
SyntheticAtmosphere said:
What brand and size of SRI do you have? Without a tune, your ECM might have problems making the proper calculations. The first action in a tune is to calibrate your intake before doing WOTs. The dp could potentially be an issue down the road without proper mods/tuning...You dont mention upgraded hpfp internals which are 101% required.
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I understand I need the upgraded internals which will be coming soon. I want to fix the misfire first. Then I’ll be getting everything else needed. The Sri was on the car when I bought previous owner said it was on there before he purchased. An it’s a sure performance 3” intake with Cobb turbo inlet hose.
 
Cfoldone said:
I didn't read if you have a AP, so do you have one and logs? Once you post some with correct logging parameters. Look on forum for more. The list of work done is great. Logs though are like Candy to a kid here. Lot more interactive help once others look at logs. No AP?. Spent just enough for a compatible cable and Download free VersaTune version to log stuff..
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I have a v2 which is trash lol an I’m got the versa tuner but the problem with that is my girl done forgot the password to the laptop.
 
3" intake needs a proper tune and at this point upgraded hpfp internals. What else is in your mod list? If a downpipe is on your car stop driving it and get the internals upgraded. Corksport has a combo deal too.

I had Autotech but they seized in my pump so I went Corksport.
 
The misfiring gang said:
Didn’t even think of that, how would you be able to tell without replacing?
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You would have to take off the valve cover and look at all the camshaft lobes. They would be excessively sharp, cracked or flat on the tip. But the chances of this are very slim. It seems by your initial post you have changed so much stuff that should have corrected a misfire but yet it is still there.

@Raider is right about the intake, HPFP internals, and a tune. Stop driving the car until you can get that sorted. My suggestion was simply an out of the box idea since you have already checked a lot.

Is the code only a generic P0300 or have you been able to isolate it to a specific cylinder in any way? I know some scan tools can show cylinder specific misfire count. I am not sure if our ECMs can show that data but if someone else knows maybe you can take it to a shop to see if they have a Snap On Zeus or Versus scan tool to see if it is a specific cylinder or not.
 
The dealer can see misfires by cylinder...that's what they told me at least. Was a bulletin about misfires on 1 and 3 potentially being a bad/worn out dual mass flywheel that led to replacing mine back in the day.
 
L337TurboZ said:
You would have to take off the valve cover and look at all the camshaft lobes. They would be excessively sharp, cracked or flat on the tip. But the chances of this are very slim. It seems by your initial post you have changed so much stuff that should have corrected a misfire but yet it is still there.

@Raider is right about the intake, HPFP internals, and a tune. Stop driving the car until you can get that sorted. My suggestion was simply an out of the box idea since you have already checked a lot.

Is the code only a generic P0300 or have you been able to isolate it to a specific cylinder in any way? I know some scan tools can show cylinder specific misfire count. I am not sure if our ECMs can show that data but if someone else knows maybe you can take it to a shop to see if they have a Snap On Zeus or Versus scan tool to see if it is a specific cylinder or not.
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They were coming from cylinder 2 and 3, haven’t checked it since I’ve done the harness, injectors and catless dp. But replacing the harness has seem to clear up my 202 and 203 codes. But will be checking it out when my work schedule frees back up. And the car doesn’t misfire under light loads or normal driving. At all. Just under heavy loads
 
L337TurboZ said:
You would have to take off the valve cover and look at all the camshaft lobes. They would be excessively sharp, cracked or flat on the tip. But the chances of this are very slim. It seems by your initial post you have changed so much stuff that should have corrected a misfire but yet it is still there.

@Raider is right about the intake, HPFP internals, and a tune. Stop driving the car until you can get that sorted. My suggestion was simply an out of the box idea since you have already checked a lot.

Is the code only a generic P0300 or have you been able to isolate it to a specific cylinder in any way? I know some scan tools can show cylinder specific misfire count. I am not sure if our ECMs can show that data but if someone else knows maybe you can take it to a shop to see if they have a Snap On Zeus or Versus scan tool to see if it is a specific cylinder or not.
Click to expand...
And yes. Just p300
 
Easter Bunny said:
You need at least a maf cal in order to run that intake.
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The car has 202k on it an the intank was on the car when I purchased it at 195k the person I got it from purchased it at 186k which he said the intank was already on the car when He purchased. The owner before him had owned the car since new.
 
That all sounds really familiar to my issue. Did you manage to find the guilty part?

I'm curious if you've gotten any logs where you could check rpm, load and ignition timing, and if that would show ecu retards timing when on boost under high load.
 
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