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Discussion Starter · #1 ·
05’ 4 motion1.8t AWM
CEL codes p0300,p0301,p0302,p0303,p0304
Came out of nowhere one cold December morning. Vacuum lines/valves checked thoroughly. Spark plugs clean. Coil packs rearranged. Disconnected/reconnected battery. MAF was recently replaced.
The curious thing is that I remove the SAIP pump annually after inspection to save it from being waterlogged and live with p0411 for twelve months, but after removal from last inspection (October 20’) p0411 didn’t trigger. Another curious event the other day was the trip miles and trip time showing extremely high values. The car hasn’t been driven for awhile. I also reconnected the SAIP but it didn’t activate from cold start.
 

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Discussion Starter · #2 · (Edited)
Eek, looks like I’m in a real pickle. Failed to mention there is also very light smoke emanating from the oil fill cap when it’s running.
 

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The smoke you are seeing could be normal just from the engine being hot. Did the misfire switch when swapping coils? Also which plugs are you using these engines are picky with plugs, NGK and denso seem to work without issues, Usually coils are the biggest culprit when it comes to misfires in these engines. If the coils you have are old or never replaced it might not hurt to go and replace them anyway.
 

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Are there any other codes, did you scan with VCDS or other VAG specific scanner ?
If you have a CPU Power Supply Relay, I suggest you replace it.
 

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Discussion Starter · #5 ·
The misfires are happening in every cylinder, so swapping the coil packs didn’t change anything. The spark plugs are oem and low miles. I don’t have vagcom. Codes are random misfire and misfire for each cylinder 1-4 only. I do have a CPU PSR. Would replacing that address the misfire issue? This is really baking my noodle. I can’t imagine all the coil packs crapping out at the same time.
 

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I’d start with replacing the power supply. After that If you have a spark tester use that and see if your coils are firing
 

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plugs need to be gapped correctly ,which I assume are. You mention two things of interest MAF and SAIP. Double check your connections and wires to and from it. And as to the SAIP, I would make sure your combi valve is functioning correctly, I suspect it is stuck open, last but not least, check/clean your the plug/ignitor ground connection on your head. Are the misfires the only codes appearing.
 

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The misfires are happening in every cylinder, so swapping the coil packs didn’t change anything. The spark plugs are oem and low miles. I don’t have vagcom. Codes are random misfire and misfire for each cylinder 1-4 only. I do have a CPU PSR. Would replacing that address the misfire issue? This is really baking my noodle. I can’t imagine all the coil packs crapping out at the same time.
It is a common cause of issues like you have, that is why I suggested replacing the CPU Power Supply Relay.
 

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as a caveat to Tomvw,s post, I have replaced these a few times, I always disconnect negative battery cable/terminal, open up CPU/ECM. The relay number is #429 and I always use VW OEM. It is O.K. to use a "value" relay for stuff like wipers etc. but in this case OEM. I always try and do a forensic of stuff I replace and the last #429 I took out had major pitting, I mean 20 years later it should. While you are in there check the 40 amp SAIP fuse and its associated relay #373 no OEM needed. That relay if original, probably is toast ,throw it at the chickens. It should be super pitted if original. Now if that #429 does or does not fix the problem it is money still well spent, takes it out of the equation and more than likely worn out/tired.
 

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Discussion Starter · #10 ·
Replaced power supply relay 429 and SAIP relay 373. Power came back to the SAIP but unfortunately the misfires continue.
 

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hang in there ,I went back and looked over posts again and thought I had mentioned it . If I recall just in front of number 1 ignitor, it is where the 2 ground wires attach ,remove nut clean. I would also check pinouts to ignitors from ECU bonnet to each of the ignitor harnesses. Do you have a Bentley? What year and engine code ?
 

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Discussion Starter · #13 ·
2005 AWM. No Bentley. Power returned to the SAIP the first time I installed a different 373 relay. Subsequent cold starts the SAIP hasn’t triggered nor does swapping the relays help (I have a couple on hand). I will be trying new coil packs this week and will give the grounds a cleaning.
 

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2005 AWM. No Bentley. Power returned to the SAIP the first time I installed a different 373 relay. Subsequent cold starts the SAIP hasn’t triggered nor does swapping the relays help (I have a couple on hand). I will be trying new coil packs this week and will give the grounds a cleaning.
the reason I ask about the Bentley is it has wiring diagram with the pinout numbers, the only issue that should bear caution when checking the continuity is it should be done "stress tested" with a small turn signal bulb or equivalent, in a manner that forces the individual wire to carry a small load. Once the ground wires are secured start car and wriggle/move harness around , this is low voltage so you will not get shocked. This could possibly make the misfire better or worse. If you have not checked combi ,block it off with a plug of some sort by removing the rubber connection coming from the SAIP.
 

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btw on the way home thinking about this ,have you done a "throttle body adaptation" since disconnecting battery and MAF replacement, also on your laundry list clean MAP sensor as they can get "oil logged"
 

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Plug wires? They are known to be a problem after getting baked crisply for 15-20 years atop the cylinder heads. (Edit: never mind, only for the V6)

Also, the hard lines for vacuum (e.g., in the rear, going to the combi valves) often become brittle and crack.
 

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The chance of having all 4 coil packs faulty at the same time is almost nil.
I suggest you check the wiring to the coil packs as chief suggested.
 

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Discussion Starter · #18 ·
Tried new coil packs, cleaned map sensor, cleaned coil ground, checked combi valve lines, rearranged spark plugs, jiggled wires. Nothing. Noticed there is moisture on the top of piston 1. The misfire codes are random. Was getting just 301 after a few starts. Then 300, 302, 301.
 

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Tried new coil packs, cleaned map sensor, cleaned coil ground, checked combi valve lines, rearranged spark plugs, jiggled wires. Nothing. Noticed there is moisture on the top of piston 1. The misfire codes are random. Was getting just 301 after a few starts. Then 300, 302, 301.
This could indicate flooding, you might have a faulty CTS at the back of the engine.
 
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