WTFitsCarter

Hi Everyone,

I have a 2005 997S mods include IMS upgrade, Quaife, sachs sport disc. 65K on the clock

Anyways i had a CEL which came up flashing.. Car drove fine for a few hours then it started to lose power a bit and was making an awful sound. Hard to replicate since i shut it off asap. Anyway I had it towed to my mechanic (he is good!) scan came up as P0301 (misfire cylinder 1) Anyways he performed a leak-down test for a piece of mind and found all cylinders to be in the 9-11% range. He then changed out the plugs and coils and the CEL came back on again boom misfire cylinder one..

he put it aside for now since he has a few other cars he needs to get to but any ideas one what else could cause the misfire in the one cylinder?

Thanks!
Carter

Macster

What did the plug from the #1 cylinder look like?

May not make much difference. I do not like to read the engine was making an awful sound.

However, awful is in the ear of the listener. Was the sound truely awful like well I don't know how to describe it, but let me try another tack.

Because these engines sound so good, run so smooth when they run right, anytime they get sick whether is it a bad coil or the engine's near total death, because the engine is not running right the difference can be like night and day and naturally one will think 'awful' when a more experienced person will know the noise is *not* that awful.

But how the engine sounds is important.

But to make matters worse since the engine may well be teetering on the edge, I'd not advise you run the engine any at all. Save whatever running is left in the engine (in case it is truely sick sick sick) for the tech to make his diagnosis.

However, he heard the engine running and apparently he didn't think it scary enough enough to advise you to not run the engine... I don't know. I'm a bit concerned you may not be getting the best service. But if you trust you mechanic. And he is at the car while I'm just at my computer. Nevermind.

Ok. If the engine is just sounding awful because it is running poorly and not at death's door, and the check engine light was flashing which means the engine controller detected a condition (misfire in this case) which is dumping unburned fuel in the exhaust and this puts the converter at risk.

The plug change didn't help so this pretty much eliminates the plug, but not the coil of course. (One trick is to swap coils and see if the misfire follows the coil or stays put.)

So that leaves the injector. It is possible the #1 injector is bad, leaking.

Or possibility is there is a burned valve. A leakdown test might not detect this. One thing that gets done during a leak down test is one listens very carefully at the intake runners and the exhust runners to listen for sounds of air making it past an intake or exhaust valve.

One listens at the oil filler tube for any air coming through which could be a cylinder/piston problem.

If this wasn't done or if the valve ain't that bad yet...

If the engine is truely making awful noises though... A bit of running might be necessary to listen to the engine at various locations (with a mechanic's stethescope) to determine as best as one can if the noise is coming from the IMS area, from under a camshaft cover, or from deeper in the head or from deep from within the crankcase.

Sincerely,

Macster.

WTFitsCarter

Thanks for taking the time to reply. The mechanic I use is world class and well respected within the area. He had to put my car aside because 4 cars came back from VIR and he needed t fulfill those commitments first. I am thinking it's a bad injector as well. He seems to want to check the signal line coming from the dme to the coil. Not sure how I feel about that but it's possible he checked the injector already.
Thoughts?

WTFitsCarter

Oh and the horrible sound seemed to be from the car running poorly not something catastrophic happening. Almost like a sputtering sound.. Hard to remember it

Quadcammer

9 to 11% leakdown is pretty high fwiw

Chip McCoy

Carter,
I have the same model and year--2005 C2S, mine alternated between plugs 1, 3 and 5 misfiring. First they replaced the coils, which were cracked, problem came back two weeks later. Just talked to the Sewickley Porsche service manager, Dwayne and the problem was the DME. So $2200 for DME, +$700 for diagnostics...car only had 35K miles on it. Keep in touch, maybe we can get a recall out of it. Porsche North America is following this one although my car is out of warranty. My next job is back in Stuttgart with AFRICA Command and I'm fluent in German so even if Porsche North America is not interested maybe the Porsche CEO Mueller will be
Sincerely, Chip McCoy
chipc4s@yahoo.de

fontana302

9 to 11% leakdown is fine.

Set national records in blown drag cars with more than that. Low leak down figures (from Gapless rings, tight end gaps) don't necessarily equate to improved performance under operating conditions.

If 1 hole was way different I'd be worried.

Leak down is much better than compressions test............

Quadcammer

are you mad? Did you really just compare a BLOWN DRAG CAR to a factory 997 engine? Obviously with a blown motor, you are going to be running huge ring gaps and the 2618 pistons will require bigger p/w clearance.

Generally, an engine that leaks down less will perform better, that doesn't take an engineering degree to figure out.

hell, if a 993 were to leak down 11%, it'd be in the shop for new valve guides.

2fas4u

Let's hope it's the injector, cause if not there isn't much else in that cylinder except for the valve, which my guess is if it's not the injector a valve guide or very slight bend in the valve. hope i'm wrong just my .02

2fas4u

Oh and by the way sorry for double post but I had a misfire one cylinder and it was the injector. However had a friend with a misfire and his was a slightly bent valve.

WTFitsCarter

DME should be covered under the federal emissions warranty that last 8years of 80,000 miles. it specifically lists the computer (ECU) as one of the components. you should try and get your money back!!

I am praying its the computer and not a bent valve.

My mechanic did a boroscope of the cylinder and it was fine. he rotated the injectors around and it still misfired, swapped coils, plugs, etc still misfired, compression test and leakdown was ok as stated. nothing that would cause a misfire. He also made a harness and used an oscilloscope and compared the readings for cylinder number 1 and 6 which they were the same. so i am guessing the computer isn't telling the injector when to fire correctly or when to fire the coil (off time?)

BTW their are NO misfires until about 3 minutes when the car starts to warm up then it misfires like crazy.

So what did the bill run you with a bent valve????

s2Rick

I have an 05 c2.Have the same problems @ low rpm. My mech thinks its the ethanol in the fuel as my car sat for 3 wks and showed up after starting. New coils ,plugs runs better but still misfires. My mech has talked to other porsche mechanics and they all told him that the ethanol is causing lots of problems.

WTFitsCarter

Figured out the problem.. It was a stuck lifter on cylinder #1. it was wierd the car would run great on cold start and in the upper rpms but miss fire at idle.. opened it up and it was the stuck innerlifter on the main lifter. $2200 repair bill coming my way

gota911

Sorry about the bill, but glad you found the problem. Thanks for the update.