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Engine Failure 2003 996 C4S 118,000 miles, Gearbox failure and replace


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I have an ongoing thread on the Porsche Club GB Website. The thread title is "Mis-fire Problem".

http://www.porscheclubgbforum.com/tm.asp?m=242384

The first entry is below. I've had some very useful comments from fellow club members and thought it might be useful for reference here and any comments the Renntech forum members might have. The latest entry on the thread confirms that the engine is being taken out for deeper level investigation and hopefully a fix.

Mis-fire problem.

I would be grateful if anyone one would comment and/or give me any advice regarding the problem below. Apologies if it appears somewhat verbose, but I felt that if I missed anything out, the full picture would not be understood.

I have a 2003 996 C4S and current mileage is 117,907 (114,071 of those done by me as it’s a business car). The car’s been serviced at the relevant mileage intervals. No running problems have been encountered until the last 10 days.

On the first frosty morning of this autumn (November 1st) I started the car and immediately noticed unevenness in the engine performance on tick over. The car vibrated as if there was an imbalance in the number of cylinders firing and the “Check” warning light came on as well as the “Drive to Workshop” message. On listening to the exhaust note there was a distinct “chugging” and intermittent “pop” from the nearside exhaust. The offside exhaust sounded normal. When the car was driven a short distance however, the performance did not seem to be impacted but the “lumpiness” and “chugging” persisted on tick over.

Upon underside engine inspection, a faulty coil pack was suspected. Subsequent diagnosis at an OPC indicated a coil pack problem. The condition of one coil pack was particularly poor and others were showing the signs of splitting, so all six were changed on November 3rd. It was noted at the time the work was done, that the nearside exhaust showed more emission deposits than the offside one i.e. it was blacker

All seemed well until the same symptoms, or be they not quite as severe as when they first appeared, recurred the day after the coil packs were changed. Again the performance under normal driving did not appear to be impacted. After some miles being covered the check warning light went out. This resulted in a second visit to another OPC on November 8th. The diagnosis this time indicated a problem on cylinder number 6. Consequently a different coil pack and spark plug for the cylinder were tried but the diagnosis persisted. The suggestion was that it could possibly be a broken valve spring but this I believe does not fit in with the problem being an intermittent one and only being noticeable on tick over. Whilst driving home, around 120 miles, the warning light and message did not appear but I did notice on a couple of occasions when I braked for a junction the “lumpiness” recurred but then cleared upon acceleration.

The charge from the alternator/battery connection has now been tested as part of the problem diagnosis and has been found to be below the power reading expected. It is thought that this could be having an effect on the Engine Management System and hence causing an engine malfunction e.g. causing a cylinder/cylinders to run too rich.

The other odd thing now is that the offside exhaust outlet is now blacker than the nearside one. Also when I put my hands close to the exhausts I get the impression that the offside one is running hotter than the nearside one. Photos are attached.

I’d be interested to find out if anyone has had similar experiences and would appreciate any replies that you are able to post.

Regards

John C

Edited by Loren
Changed title to reflect issue better
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Well, the first thing I would do is find out what all the sensors reading are on the engine. This should have been collected by the dealer or you can get the info from your own scanner. Record LTFT, STFT, MAF, engine load, timing, intake temp and coolant temp at idle on warm engine. Also, record the after cat O2 sensor readings at warm idle for both banks.

From this info, we may be able to better see what the engine is doing, if anything, differently from one bank to the other. A vacuum check will show valve problems, but this is beyond the most modern day mechanics as they have never been taught how an engine works, but only on how to read a computer printout.

What is the measured voltage output from the alternator on warm engine at idle?

Edited by 1999Porsche911
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Johnny, sorry to hear about your problem. I hope it turns out to be something simple. Anyway, please be sure to let us know what becomes of this. Cheers.

Thanks for your thoughts. The engine's being taken out of the car today as when the sump was inspected a small fragment of "white metal" (Bebbitt Metal) was found and this could be off the Intermediate Shaft Bearing. Won't know for sure until further dismantling.

The OPC where I bought the car from did say that they had experieced a misfire moving from one bank of cylinders to the other caused by swarf getting into the tappets. However this was on a brand new car and they wouldn't expect it to happen after 118,000 miles unless it was a component breaking down.

So whether the two are linked and this has resulted in the moving misfire, we'll have to wait and see.

Rgds

JCR

Edited by Johnnyceesred
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If it makes you feel better, I have a 2002 C2 coupe with 125k miles on it and I just found out that I'm going to need a new engine in the near future. It's nothing I did. It's just worn out . . . It's leaking oil past the exhaust valve stem seals and a lot is getting into the combustion chambers. It's causing the computer to cancel fuel to injector on that cylinder(s) because it's sensing crappy combustion byproducts. The check engine light keeps coming on because of it too.

Also, about half the coil packs needed replacing too. I drive my car in the rain, snow (with salted roads) and the coil packs couldn't handle that.

People are always asking how long will these 996's last and I guess it's around 118k-125k miles!

b-man

Edited by b-man
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There's a guy on porsche-1.net had very similar prognosis to yours.

They went thru the same thing. changed out coil packs. But the problem persisted. Anyway, it turned out to be a faulty throttle body. Hope this helps.

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  • 2 weeks later...

B-man and Scouser,

Thanks for the replies. I'll keep the thread updated with progress on mine.

The main challenges have been to find out what's causing the misfire given we've had 2 different diagnoses from 2 OPCs (1st one was a coil pack failure, hence all 6 coil packs were changed considering the high mileage, and the 2nd was misfire on cylinder 6) and why the misfire moved from one bank of cylinders to the other 2 days after the 2nd PIWIS diagnosis.

Rgds

JCR

Edited by Johnnyceesred
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  • 2 weeks later...

Thanks for the 2 latest posts. The engine's out and in an almost dismantled state. Some evidence has been uncovered regarding corrosion in the connecting rods in the engine block. Will know more and report back (maybe with photos) between Christmas and early January.

Happy Christmas to all members and a good New Year.

Rgds

JCR

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I found out that I'm also having problems with a solenoid that controls the variocam (valve timing). It's not working on one side of the engine so it's throwing off some things. I understand the solenoid is dificult to get to and therefore, very expensive to replace.

b-man

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Hope everyone had a good Christmas and Happy New Year to you all.

The engine has been dismantled and there are some concerns about the crank block.

1. Some striations have been found on one half of the crank block as if something has gouged out metal from parts of it.

2. There are cracks in the steel elements of the crank block.

3. The profile of the steel elements of the crank block differ between the two halves.

I'll attach photos to illustrate the above.

We're not sure whether these symptoms are the cause of the original misfire or additional to it. I'll report back on further results when more is known after the New Year holiday.

Best regards

John

post-15363-1167429488_thumb.jpg

post-15363-1167429500_thumb.jpg

post-15363-1167429512_thumb.jpg

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Just a "far shot" from my yesterday experience with similar problem...

- the car is a MY06 987 with a 3.6 997 engine installed (!)

- car developed very bad idle from noticeable shaking on the wheel to detonation and engine stall within 5 days and 500 miles (all started when weather turned cold)

- CEL light kept coming on after a few minutes of idle, giving every code from 300 to 306 (random misfire and all cylinders misfire)

- checked with generic OBD readers and later with Durametric, found that MAF reads way lower than it should be, while ignition timing going crazy between -4 and +11 degrees

- replaced MAF, replaced all spark plugs, replaced one coil pack, replaced air filter, removed and checked throttle body, whole intake tubing, checked exhaust with tailpipe sensor (obviously very bad values everywhere, 700ppm CH or so...), checked both valve lifting and valve timing electronics - still no joy.

We were preparing to remove the engine when "just my 2c's" removed the breather hose between the oil separator and the intake manifold (the thicker one). Closing the hole on the intake manifold cured the problems - and later found that the :censored: tube developed a very thin crack on the lower side. Unnoticeable otherwise but the vacuum probably sucked it inwards and opened up the gap. This way air could get into the engine passing by both the MAF and the throttle valve, but only when there was enough vacuum from the previous engine revolutions to open the gap. Hence the jumpy-detonating-CEL-throwing idle... :lightbulb:

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Just a "far shot" from my yesterday experience with similar problem...

- the car is a MY06 987 with a 3.6 997 engine installed (!)

- car developed very bad idle from noticeable shaking on the wheel to detonation and engine stall within 5 days and 500 miles (all started when weather turned cold)

- CEL light kept coming on after a few minutes of idle, giving every code from 300 to 306 (random misfire and all cylinders misfire)

- checked with generic OBD readers and later with Durametric, found that MAF reads way lower than it should be, while ignition timing going crazy between -4 and +11 degrees

- replaced MAF, replaced all spark plugs, replaced one coil pack, replaced air filter, removed and checked throttle body, whole intake tubing, checked exhaust with tailpipe sensor (obviously very bad values everywhere, 700ppm CH or so...), checked both valve lifting and valve timing electronics - still no joy.

We were preparing to remove the engine when "just my 2c's" removed the breather hose between the oil separator and the intake manifold (the thicker one). Closing the hole on the intake manifold cured the problems - and later found that the :censored: tube developed a very thin crack on the lower side. Unnoticeable otherwise but the vacuum probably sucked it inwards and opened up the gap. This way air could get into the engine passing by both the MAF and the throttle valve, but only when there was enough vacuum from the previous engine revolutions to open the gap. Hence the jumpy-detonating-CEL-throwing idle... :lightbulb:

Hi and thanks for your reply.

Did the misfire move from one bank of cylinders to the other bank as mine did?

As the engine's now totally dismantled it will give the independant specialist a chance to inspect all tubes connectors etc. Our collective worry is the state of parts of the one crank block half as seen in the first thumbnail on my last post. My hope is that an authoratitive technical specialist from Porsche GB or maybe even Stuttgart if necessary, will come out and view the engine in its current state and give us a verdict on what he/she sees. I also spotted some further gouging in another part of the engine casing but we're not sure whether this was done at the factory to remove some imperfections in the casting or for some other reason.

Anyway I'll let you know more as things develop.

Best regards

John

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The symptoms - a little bit more in detail - were:

1. Noticeable uneven idle, practically a bad feelingof a "missing heartbeat" on the wheel

2. A day later it could be seen a passenger seat back shaking while at idle

3. Meanwhile car developed an "idle dropping behavior" - coasting from high RPM, depressing clutch, idle fell down to 400ish and the car either stalled (a few times) or not, idle caught up

4. Idle turned to "unacceptable", better when engine cold (but still huffing and puffing), and a very specific "tramm...tramm...tramm...tramm..." instead of the nice "dumdumdumdumdumdum" of a healthy engine. Almost as if a complete row of cylinders were not firing

5. Exhaust gas analysis showed unburnt fuel

6. CEL codes always appeared as 300 first (unspecific / multiple misfire), then within a minute all 6 cyls dropped specific misfire codes (301..306)

What helpe me a lot was removing literally everything / started to be _very_ suspisious when removed both MAF connector and e/gas connector and the car still idled and responded to throttle. There had to be a leak...

Will keep my fingers crossed for you!

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Btw, could you take a picture of those marks from right angle, possibly with macro setting, but lighting kept at a low sweeping angle? Some of us here with some machining/milling experience could have a bet if those are finishing moves from the manufacturing process or impact humps because of a loose part running amok inside your engine...

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Btw, could you take a picture of those marks from right angle, possibly with macro setting, but lighting kept at a low sweeping angle? Some of us here with some machining/milling experience could have a bet if those are finishing moves from the manufacturing process or impact humps because of a loose part running amok inside your engine...

Hi again,

I really appreciate your last 2 posts, thankyou.

Regarding the difference in sound, when the problem first appeared at tickover, as you described the tone was different between the nearside exhaust affected by the misfire and the offside exhaust which seemed unaffected by any problem. Revving the engine and driving the car a short distance sounded and felt OK. This first situation resulted in a "coil pack failure" reading from the diagnostics done at the 1st OPC I took it to and so I had all 6 coil packs changed in consideration of the mileage and condition of the other 5 coil packs.

When the CEL light recurred within 24 hours of the coil pack change, a second PIWIS test 4 days later at the OPC I bought the car from 3 years ago, indicated a misfire on clinder 6. Their advice was that it could be a broken valve spring and they estimated a labour cost of £2,500 + Tax to get the engine out and tell me whether they were right or not.

When the problem switched to the offside exhaust and associated cylinders the tone became more like a tugboat "chugging" sound accompanied by "popping". Revving the engine at that stage resulted in a "spluttering" tone. I tried reversing the car a short distance off my driveway but the misfire seemed too severe to risk any distance driving, so I called roadside assistance and had the vehicle towed to the independent about 20 miles away from my home.

He did the usual emissions reading and found the offside exhaust at around 820+.

Looking at the randomness of the marks and the fact that there appears to be a crack in the steel insert as shown in my first photo of the 3 thumbnails, I don't think its finishing moves but next time I'm over at the indie, I'll take the camera anyway and try to provide the type of photo you requested. I'll also try and attach a higher quality photo to this post if the file size is OK with the web site settings along with a photo of the car from the showroom. It looked great and you'll probably appreciate why I bought it.

Thanks and regards

John

post-15363-1167494497_thumb.jpg

post-15363-1167494856_thumb.jpg

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Thanks for the picture repost, now I'm almost sure that those marks are not part of the manufacturing process. However, the parallel meandering "valleys" give me a hint of something really big went loose in there (at least the size of a dime, maybe a few coils from spring?!?!?!) Just my uneducated guesswork...

Btw, the car looks marvelous, no wonder you fell in love with it :D And rest assured, there is no such thing as engine beyond repair - maybe some parts will have to be replaced, but you'll have it purring on the road soon...

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Hi again,

Glad the better photo gave you more info to assess. Any thoughts on what appear to be cracks in the darker sections? The indie hasn't mentioned finding any broken springs which was one of the early potential suggestions.

Thanks for your comments on the car as well.

With regard to the car itself it's my first Porsche, I was driving a M3 at the time I saw it. I had taken some time out for lunch (which is unusual for me as I often use the time to travel between clients, catching up on e-mails etc.) and chose to look around that OPC. My first words to the salesman were "I'll be honest with you I'm not buying but is it OK just to browse?" Just shows how wrong you can be!!!

The combination of the Cobalt Blue paintwork, the red calipers and the alloys had me hooked. More importantly my wife loved it too (she hated the M3 for some reason). It was their ex-demonstrator and as I sold the M3 myself I got a £500 off their asking price.

I'll do some more web searching to see if I can find some more info on the inserts in the crank block and try and post some links if I find anything useful.

Rgds

John

Edited by Johnnyceesred
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I have no idea about the molding process of the casing - but those two black stripes that protrude from the bearing area may also be "handles" used to position and hold the black/ish (porous iron / carbon-rich steel?) core while the aluminum/magnesium/silica being cast around it. In this case those breaks would really mean no harm to the engine. Meanwhile it is a little bit strange that those "impact marks" appear at the same place... Entirely speculation - but it will be soooo nice when you find out what happened and let me know that all my ideas were just... hmmm... bad guesses :D

As for the loose part - have you cut up the oil filter?

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The specialist cut open the oil filter after he had found a small flake of metal (possibly bearing metal i.e "white metal" or Bebbitt metal) in the sump. Nothing else was found in the filter.

Also did you notice that the profiles of the inserts differed between the two halves in the thumbnail photos? I can't see why there should be "handles" in one half and not in the other.

Rgds

John

Edited by Johnnyceesred
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You're right about the assymetry - how about molding the cast iron part all at once as one piece (hence the need for the "handles" to pour metal in / let air out of the sand mold), then slice it up, then use these one-per-bearing slices as the "core" for light alloy molding? :D Now would really like to hear the truth about these composite crankcases - but still love guessing :D :D :D

I wonder if ToolPants or Loren could comment these pictures (especially about the scratch marks / cracks)?

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If you are talking about the wear marks on the (aluminum looking) bearings - they don't look bad to me. But for the cost of a new set of bearing I always replace them whenever I split an engine case. Just not worth tearing the engine apart again in 20,000 miles. Those bearing come out and are easily replaced.

If the case is cracked at a non-critical point it can be welded (at a specialty shop) - but if the crack is at a critical bearing point then case should be replaced. The one picture looks to me like the latter. - a main bearing support is cracked.

I would like to hear Porsche's opinion on an engine that shows very little wear on the main bearings yet the bearing support(s) are cracked. This should not happen IMHO.

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Looks like we're into very a interesting topic and I like your suggestion.

I did note that the the profile of the insert on the other side of the indvidual section was not the same as the side showing either one "handle" or two "handles" i.e. the other side was similar to the other half of the crank block which had no "handles" at all. Therefore these "handles" do not span the thickness of the sections. (Hope I've explained myself adequately, photos can say so much more!!!). If the inserts are there to provide strength and higher performance characteristics (as I understand the earlier all-alloy crank blocks were problematical), wouldn't they be forged rather than cast?

I tried various web searches for other crank block pictures but didn't come up with anything positive yet. After searching different links and discovering different part names, I question whether the right term for the parts in the photos is crank block, crankcase or crank cradle. Any thoughts?

Rgds

John

Edited by Johnnyceesred
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If you are talking about the wear marks on the (aluminum looking) bearings - they don't look bad to me. But for the cost of a new set of bearing I always replace them whenever I split an engine case. Just not worth tearing the engine apart again in 20,000 miles. Those bearing come out and are easily replaced.

If the case is cracked at a non-critical point it can be welded (at a specialty shop) - but if the crack is at a critical bearing point then case should be replaced. The one picture looks to me like the latter. - a main bearing support is cracked.

I would like to hear Porsche's opinion on an engine that shows very little wear on the main bearings yet the bearing support(s) are cracked. This should not happen IMHO.

Hi Loren,

Thankyou for your input.

My concern isn't with the semi-circular bearing inserts but I'm focusing on the darker colour metal. Attached is a photo showing the difference in the profiles of the dark metal sections in one half of the crank block where the damage has occurred (the other half looks fine) i.e. some have no elongations into the alloy sections, some have one and some have 3. This is quite different to the other half of the block (see previous photos). Is this normal and do you know where there might be other photos to compare with?

I hope that we can get a reasonbly quick response from PCGB after the holidays and get some expertise on the situation.

Happy New Year to all and thanks to everyone for viewing and commenting on the topic.

Best regards

John

post-15363-1167570830_thumb.jpg

Edited by Johnnyceesred
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