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Multiple Cylinder Misfire - 2002 996 3.6 Cabriolet


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I am having an intermittent misfire issue with my 996.  It started a few months ago, when the battery ran down after not driving it for a few weeks, and I had to jump the car to get it going.  After a few miles, I got a CEL and the car started to misfire.  Upon arriving at my location, which was just a short distance away, I turned off the engine and went about my business.  Upon returning to the car, it ran fine.  No CEL and did 65mph all the way home, which was about 20 miles away.

All was good, until a couple of weeks ago, when on a slow drive, I got a misfire and the CEL came back on.  I made it to a gas station to fill up, expecting it to clear again.  This time it did not, and I limped it on home.  After a couple of days, I went out to diagnose and checked codes.  They were:

P0300- PFC 507 – Misfire detected

P0301 – PFC 508 – Misfire Cylinder 1

P0305 – PFC 513 – Misfire Cylinder 5

P0303 – PFC 512 – Misfire Cylinder 3

P0304 – PFC 511 – Misfire Cylinder 4

 

These are on both banks.

After a couple of days, I went out, cleared the codes, and the car ran just fine.  No CEL and smooth running.  I drove it a couple of times, without incident.

 However, today, I went out to drive the car.  Went a short distance…all was fine.  When I got back into the car, I once again had misfires and the CEL came on.  Checked codes and all I have is:

 P0300- PFC 507 – Misfire detected

P0301 – PFC 508 – Misfire Cylinder 1

 The only thing I can think of is that it must either be related to a low voltage battery messing with the computer or somehow related to moisture, since both incidences occurred around having just completed a rain storm.  The car was not driven in the rain.  This would possibly point to bad coils.

 I have checked the MAF, but disconnecting the plug, when it was misfiring.  No change in idle.

Seems strange to have multiple Coils fail at once?  But possible.  Same with spark plugs.

 One item of note.  This is a replacement engine, replaced by Porsche, due to an engine failure while the PO owned it.  The current engine has about 30K miles on it.  I am not sure if all the maintenance parts were replaced, such as AOS, coils, plugs, and so on.

 Any thoughts on what to check to help narrow down the issue, other than just replacing everything or taking it to the repair shop?

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As Uwon suggests the coils are the prime suspect for exactly the reason stated.

 

That being said, if the battery is tested as being in an under-volt condition, this can cause some unusual problems. The PPI performed on my car reported that the battery was holding at under 12 volts. The day after I bought my car the Tiptronic transmission went into Limp Mode and only allowed shifting up to third gear forcing me to bring it to Porsche as their PIWIS was required to clear the Limp Mode. Prior to going to Porsche I replaced the battery. After Porsche cleared the fault everything was, and continues to be, normal. The problem occurred because the battery voltage was low. This explanation is not intended to negate the high probability that the coils are faulty, it's just a recommendation to check the battery as well.

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iI agree that the coils are a prime suspect.  However, I also have to ask the obvious question.  What is the likelihood that multiple coils went bad at exactly the same time?  If it was one coil, that would be a perfectly acceptable, but three or four?  Also, the car was not driven in the rain and the roadway was not wet.  I am going to check the battery voltage level, and take it from there.  I hate to throw parts at a problem, but I am going to assume that when the engine swap occurred, that they just swapped over everything from one engine to the other, and the coils and plugs, might be the original ones.  The paperwork shows only the engine, and not of the maintenance items being replaced.

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6 minutes ago, TNT79Bronco said:

iI agree that the coils are a prime suspect.  However, I also have to ask the obvious question.  What is the likelihood that multiple coils went bad at exactly the same time? 

 

Actually, it is pretty high based upon experience.  I would pull the coils and look for small cracks, the give away sign that the coils are on their way out.

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JFP is one of those who knows! The cost to pull the coils is your time.

 

I just changed mine with 44,000 miles on 'em and three of them had huge cracks, two had hairlines, and one looked ok. I logged misfires using Durametric in two cylinders frequently and three other cylinders less frequently even though it never threw any codes, the engine just seemed down on power and misfired and ran very rough only a few times while standing at stops. Even without the cracks I was planning on replacing them simply based on the misfires logged by the computer, I figured it was time.

 

Again, the battery check is not so much to diagnose a misfire, but it may be that it contributed to setting-off the misfire codes "all of a sudden". Just one piece of a possible puzzle that hopefully only has a couple pieces to it.

 

After checking original coils, I'd be shocked if they weren't toast, I would get new coils, screws, plugs, dielectric grease (for the boots and plug porcelain as indicated on Beru's site), and a really tiny dab of anti-seize on the plug threads. I put a small amount of dielectric on the outside body of the coil's electrical socket (on far left in photo) to aid in slipping the connector cover back over the socket, I couldn't make it work otherwise.

 

 

coiltop.JPG

edit: this coil is the latest and is the part that my local Porsche dealer keeps in stock for Boxster, Cayman, 911 and covers many of the years. When I saw that it didn't have Beru on the coil (it's stamped Beru on the boot), I reconfirmed with Porsche that this is the correct part because searches didn't know this part number.

Edited by ttocs
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The issue isn't going to disappear just by clearing codes.  The codes are telling you something is wrong.  Spark plugs and coils are a maintenance item.  How long has it been since either have been replaced?  Cracked coils are common and will cause the problems you are having.  Get some new upgraded coils packs.

 

new coil pack.JPG

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9 hours ago, TNT79Bronco said:

iI agree that the coils are a prime suspect.  However, I also have to ask the obvious question.  What is the likelihood that multiple coils went bad at exactly the same time?  

Hence my qualification if themissfire happens in damp/rainy weather where deteriorated coil(s) are more likely to show faults. If one is cracked surely one or more will be right behind and H2O will only serve to identify the culprits earlier. 

BTW, I share this from actual experience. Long trip through the U.S. Dry day-no issues; next day, quite humid- started misfire; third day -rain-crawled to the dealer. Multiple cylinder misfires. 

Johan

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Ok..have ordered 6 replacement coil packs, and 6 spark plugs.  Should be here in a couple of days.

 

Crazy...called my local Porsche dealership for the spark plugs.  First of all, they needed a VIN to tell me what spark plugs that goes into a 2002 996.  Then the guy tells me, that it could be one of two DIFFERENT spark plugs, based on my VIN number.  Whaaaaaaa??????  I wasn't aware they made two engines for my base 996???  So....once the guy verifies that they have my CORRECT plugs in stock....I could have them for a mere $36.00 EACH!!!  I almost fell out of my chair.  Nothing like $240 in SPARK PLUGS!!!!

 

Keeping fingers crossed that this is the issue.  Will update.......

 

(I can only imagine what blinker fluid costs there!)

 

 

 

 

Edited by TNT79Bronco
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FYI

PCA members get discounts at Porsche dealers. My dealership keeps a copy of my membership card on file so anyone I deal with in the parts dept will know to apply the appropriate discount. Usually it's 10% or 15% depending on the parts in question. An extra dealership discount can also apply (small, but still, lucky me!).

Edited by ttocs
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2 hours ago, TNT79Bronco said:

Ok..have ordered 6 replacement coil packs, and 6 spark plugs.  Should be here in a couple of days.

 

Crazy...called my local Porsche dealership for the spark plugs.  First of all, they needed a VIN to tell me what spark plugs that goes into a 2002 996.  Then the guy tells me, that it could be one of two DIFFERENT spark plugs, based on my VIN number.  Whaaaaaaa??????  I wasn't aware they made two engines for my base 996???  So....once the guy verifies that they have my CORRECT plugs in stock....I could have them for a mere $36.00 EACH!!!  I almost fell out of my chair.  Nothing like $240 in SPARK PLUGS!!!!

 

Keeping fingers crossed that this is the issue.  Will update.......

 

(I can only imagine what blinker fluid costs there!)

 

 

 

 

 

$36 a plug is more than a bit steep.  Check the same part number on board sponsor Sunset Porsche's parts website, I'll bet it is significantly better..............

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uSo I took the rear of the car apart (person who designed this should be shot), to access the coils and plugs.  So far, have only done bank 1. This is what I found. Look like there are some cracks. Hard to tell if they are fatal cracks or just surface issues. 

 

There are more pictures of the cracks, but for some reason, I get errors loading them. 

 

These are also also the plugs that I replaced. 

EE46E82F-1675-460E-8F6B-0A6406D4C5E7.jpeg

A8636A8C-BA5F-43FC-8BDE-20CA9AFD1B9B.jpeg

2BF84ED8-211A-4B78-BF9F-7EBADEB80F69.jpeg

Edited by TNT79Bronco
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I would replace spark plugs and coil packs. The car is 16 years old - plastic is going break.

If the coils test well now they may not after being hit with water. I would not put coils like that back in a car - it's just asking for future problems.

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Good job!  Coils definitely cracked all over the place.  Spark plugs look worn but good as far as no unusual problems.  Glad to hear you are replacing all coils/spark plugs. Your car will run much better.

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Images of Cracked Coils from Driver's Side

IMG_0650.JPG.12f68aca5a935975bd25ec9635ec8c42.JPGIMG_0651.JPG.0aa14ccaf04a41d948cdb53f72f2fe80.JPGIMG_0652.JPG.6fa41bf653ad6008e6937dcf2167dc25.JPGIMG_0653.JPG.af8096d5c7021fc9abb84524fae08396.JPGIMG_0654.JPG.1baebf154bbef363d7fa43cba97373d0.JPGIMG_0655.JPG.61bda217f18d2d1f1759b0491ca5a0a6.JPG

Ok, completed the replacement of the plugs and the coils last night.  BTW...who the hell thought it was a good idea to put a muffler bracket right over the spot where the middle coil goes on each side of the engine????  For those of you that are looking to do this, let me make it clear as to what I think you should do to make it easy and most efficient.

 

1.  Remove the rear bumper covers (don't forget to unplug the connector)

2.  Remove both rear tires (place on jack stands)

3.  Both outer and inner heat shields on both sides

4.  Both mufflers

5.  Drop the engine down about 1/2" or so.

 

Doing all of this might not be 100% necessary, but whatever time it costs you in doing this, will greatly save you in time, aggravation an skinned knuckles.

 

I got the replacement coils at O'Reilly's auto parts, and they were in a generic type box, but were Beru coils, and were the new design, with the longer bolts.  One of the boxes was missing the bolts, so I ran to the hardware store and got a couple of 6mmx40mm bolts to hold the coil down.  Worked just fine.  The new bolts that came with it were of a different head design.  IMG_0663.JPG.25c523541d4f2da953b093062ac01402.JPGIMG_0665.JPG.1a8fa4fb84effd862d6cfc465dbb3285.JPG

 

Before I started working on the car, I had to back it into my driveway.  It started just fine....no CEL...and no misfires.  I wasn't surprised, since it was a warm day and my suspicion is that it is mainly problematic on cold, damp days.  Naturally, I went ahead with the project.

 

New coils installed.....IMG_0666.JPG.9336b06d6233806e6295884b675570c8.JPG

 

Once I buttoned it all back up, I tried to start the car.  DEAD BATTERY!!!  It had only been sitting a few days.  Once I jumped the car, it ran just fine.

 

I am still not 100% sure that the coils were the problem, but even if they weren't, they and the spark plugs needed to be replaced.  I need to check the battery and see when it was installed and maybe have it tested to hold a charge.  If it is bad, I will replace it.  I will update the post periodically, and confirm if I have any more issues or if the problem has subsided for the long haul.

 

Oh...once I got under the car, I confirmed my suspicion, which was that I had a valve cover leak on the passenger side.  I can smell oil, when I drive and I notice that I tend to use oil at a semi increases pace.  I expect some smell and loss of oil, but it is evident that I have some leakage.  This is a replacement engine from Porsche, installed while the PO had it.  It suffered some type of catastrophic engine failure.  Not sure which one, but it was replaced under the class action lawsuit.IMG_0659.JPG.0ef52ede9cbbf3ff477528b78e0c7d3c.JPGIMG_0660.JPG.0d7996e065a4bb14b80eb412e2fc29ac.JPG

 

I am attending the Raby M96 engine rebuild school, and have pulled engines and transmissions before.  Next time I need to change the clutch, I will drop both and do some routine maintenance on the engine, that is easiest done, while it is out of the car.

IMG_0656.JPG

IMG_0657.JPG

IMG_0664.JPG

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As planned, completed the replacement of the coil packs and spark plugs. I got the new packs that came with the longer fasteners. 

 

It looks like I have a leaking valve cover. 

 

When I pulled the car into the driveway, before doing the swap, it was running fine. No CEL it was a warm day. I did the swap anyway. 

 

After the swap, I tried to start the car.....dead battery. Arrrrgggg!!!

 

Had to jump it. Started right up. Took it for a spin, and all was great. 

 

Not sure if this solved the problem for sure, but will keep updating the post. Also, I keep trying to upload pictures, but when get errors, when I try to upload load pictures. Only some so through. 

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Hey, this is all a part of owning. 996/997. I like the 996 because it is fairly easy to work on. I have dropped the engine/trans on a few other 996’s that I have owned, and can do it fairly easily and quickly. 

 

I think that is about the only way to effectively own a 996/997, ya gotta be able to do the work yourself. That’s why I am heading to Jake Raby’s engine Class. 

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