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I have 2000 Porsche Boxster S that is misfiring on nearly every cylinder. It started with symptoms of a bad MAF; typical sluggish on take off, CEL light with the corresponding code. I would disconnect the wiring from the MAF and it would clear up. I cleaned the MAF and plenum and it ran perfectly for about a day. Ordered a new MAF. By before I had a chance to put the new one in I got a flashing CEL and a massive loss of power. Put in the new MAF. It cleared up some idle issues but the loss of power and flashing CEL is still there. The codes show random misfire and misfire on 2,3,4,5, and 6. I've also changed the spark plugs but it has had no effect.

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1 hour ago, FStallcup said:

I have 2000 Porsche Boxster S that is misfiring on nearly every cylinder. It started with symptoms of a bad MAF; typical sluggish on take off, CEL light with the corresponding code. I would disconnect the wiring from the MAF and it would clear up. I cleaned the MAF and plenum and it ran perfectly for about a day. Ordered a new MAF. By before I had a chance to put the new one in I got a flashing CEL and a massive loss of power. Put in the new MAF. It cleared up some idle issues but the loss of power and flashing CEL is still there. The codes show random misfire and misfire on 2,3,4,5, and 6. I've also changed the spark plugs but it has had no effect.

 

More often than plugs, old or cracked coil packs lead to misfires.  Pull the coil packs and check them.

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33 minutes ago, FStallcup said:

Is it common that they would all go out at once?

 

 

Depends.  We sometimes get car is that had been running fine, and then developed problems after a rainy spell or they had just been washed.  Inspection showed multiple coils with cracks that were effected by moisture.

 

You need to pull the coils and closely look at them for cracks, you can also check them resistance at the same time.  Coils are like light bulbs, eventually they will fail and have to be replaced.

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1 minute ago, JFP in PA said:

 

Depends.  We sometimes get car is that had been running fine, and then developed problems after a rainy spell or they had just been washed.  Inspection showed multiple coils with cracks that were effected by moisture.

 

You need to pull the coils and closely look at them for cracks, you can also check them resistance at the same time.  Coils are like light bulbs, eventually they will fail and have to be replaced.

Very interesting.  I'll give that a shot.  Guess I'll be going down to get an OHM meter.  Any pointers on how to test?  I've never done it before.

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2 hours ago, FStallcup said:

Very interesting.  I'll give that a shot.  Guess I'll be going down to get an OHM meter.  Any pointers on how to test?  I've never done it before.

 

Check the resistance of each of the coil packs.

Resistance between terminal 1 and terminal 15 at 20°C: 0.3 - 0.7 ohms.

Any coil pack that is drastically different should be replaced.

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9 hours ago, Ahsai said:

Some more thoughts...Is your new MAF from Bosch and does it have the correct p/n? Any non-Bosch non-genuine MAF is problematic. How are your engine air filter and fuel pressure filter? Any massive intake air leak?

My MAF is from bosch and has the part number recommended by Porsche of Nashville(ending in 125.01).  My engine air filter has been cleaned within the last month.  As far as my fuel pressure filter goes, I have no idea.  The car has 184K miles on it and I have never replaced a fuel pressure filter.  I'll look into that and get back.  I don't think I have an air leak.  What are some symptoms of that?  My AOS went out a couple of years ago and that caused an air leak and unstable idle.  I replaced it and fixed the problem. I started having unstable idle again once my MAF started going out.  Now that the new one is in the idle is rock solid.  It's just running terribly otherwise.

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P1118 Oxygen Sensor Heating after TWC Bank 2.  You have a code for the rear O2 sensor heating element on bank 2.

 

When we see this code in a transient mode (goes away and comes back), it is often after the car has been wet (rain, ran through standing water, etc.).  Does any of that apply?
 

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For those reading this thread in the future, the MAFs for the 2000 base and S vary according to the build date.

 

The 124.00 part number is for:

Early 2000 (1/31/2000)

 (thru Boxster 2.7L Chassis #98 6YS 62 0414 and #98 0YU 62 5099)
(thru Boxster S 3.2L Chassis #98 0YS 66 0257 and #98 3YU 66 2413)

 

And if a 125.00 or 125.01 part is used for those cars, a reflash is required.

 

Is the car has a 125.00, a 125.91 can be used without a reflash.

 

This can be verified by consulting the PET.

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  • 2 months later...

So sorry to keep anyone waiting on a diagnosis of this if you were interested.  I took it to a Porsche repair shop and they confirmed that it was my coil packs.  They were going to charge me over $2000 to fix it!  That also included $1000 for changing the spark plug tubes which they said were leaking externally.  What a joke!  It's easier to replace the tubes than it is to replace the spark plugs; and it's an $8 part.  UNBELIEVABLE!  Anyway, I replaced the offending coils for a grand total of $80.  Car runs great now.

 

Thank you all for your opinions and advice.

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