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Multiple Misfire Codes

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I've been reading through other posts on this topic and have an idea as to where to look but wanted some guidance in hopes of narrowing it down.  I was driving home from an out of state meeting on the highway last night when suddenly the Visit Service Center message & Engine Icon popped up.   I scanned temps and pressures and all looked normal and the car had been running fine and seemed to still be until I tried to apply power to pass a truck.  I noticed a significant loss in power and rough engine.  As it was very late, I decided to nurse it home and I ran an OBDII this morning. 


Here are the codes:


P0300 Random Multiple Misfires

P0301 Cylinder 1 Misfire

P0305 Cylinder 5 Misfire

P0303 Cylinder 3 Misfire 


During my ride home, I pondered what the issue might be and was thinking coil pack, MAF, etc.  Seeing the codes for multiple cylinders is making me think coil packs are unlikely (wouldn't all fail at once) and odd that it's in both banks.  Being it's Friday and I need the car Monday I was trying to figure out what I could do this weekend to get it fixed and I don't want to go on a parts swapping binge (or worse yet have a P-Shop do it) and this could get expensive fast.


Thanks in advance

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I think it is just the opposite - coil packs can (and do) individually go bad. As well the spark plug connectors.


1. Check spark plug connectors. Resistance: approx. 2 k ohms
2. Check ignition coil(s). Resistance between terminal 1 and terminal 15 at 20°C: 0.3 - 0.7 ohms
Check the wiring while you are there - it can be damaged by road debris or weathering.
Not likely the MAF as that would affect all cylinders and can't really cause a single misfire.
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Sorry, meant to include the car details.  It's a 2006 C4S Cab with 53K mile on the clock.  Plugs were changed last year (~8K miles ago).  No recent mods or changes to the car, car was fully fueled 3-4 days ago with a little over half a tank of it used at this point.  A subsequent scan picked up a P0304 Cylinder 4 Misfire.  Starting it today, it's running much more rough than last night and backfiring if

throttle is used.

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I would suspect the following and note it may not be realistic to expect to fix it over the weekend.

1) Bad gas

2) Coils (they are likely overdue anyway if they are original)

3) MAF (can read MAF value from OBDII when driving the car)


You may also want to check the LTFT and SHFT values from the OBDII scanner. Would be the best if you have Duramatric to real Porsche-specific codes and pending codes.

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  • 4 weeks later...

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