Batman33

Well, indy mechanic number 1 failed to show up this AM at the agreed upon time. His shop is five minutes from my house! I thought it would be a good idea if he listened to the cold start up sound when, you know, the motor is actually cold. I called him out for not showing up and he offered three different excuses. I have essentially tossed him aside because after I described the noise to him (when I stopped by his shop and scheduled the appointment) he immediately wanted to blame the IMS bearing as a likely cause and he dismissed out of hand my suggestion/question that it could be a timing chain tensioner. So, I was not willing to put much faith in him anyway. And, by the way, when I visited his shop there were no Porsches around....only Bimmers and Benzs. Sort of like visiting a restaurant at dinner time and nobody is there. I know my rant does nothing for the Forum, I just have to vent to somebody! (My dog just looks at me and tilts his head!) Oh well. On to the next guy.

labdag

hi Batman33, nice thread. any update on this? thanks

Batman33

Thanks for asking, labdag. After talking with fellow 997 owners at car gatherings and reading all that I could, rightly or wrongly, I ultimately attributed the noise I was hearing to the car's normal start up sounds. It's more like a burble than something mechanical, if that makes sense. After getting caught up, as a new 997 owner, in all the doom and gloom about the IMS bearing, bore scoring and such in these forums, I simply decided to just drive the damn thing and not worry about it. I've run it hard at two HPDE weekends this summer at Summit Point with no issue. I sent a sample from the first oil change after purchase to Blackstone Labs - the related analysis and report were glowing. I also checked the over rev history with a Durametric...it had only one slight incident, in "level" 2 I believe, that was likely caused when I bounced it off the rev limiter once at Summit Point when I lost track of what I was doing for a second. I'm going to continue to maintain the car according to conventional wisdom, keep my ears open for any changes and continue to have fun and let the chips fall where they may. As I told some of my fellow HPDE participants last weekend, do you realize how lucky we are to be able to indulge ourselves with these cars?!

Batman33

PS You might say I effectively said "F___ it, let's go bowling."

Z00mie

Not an Porsche engine guy, but was thinking I'd swap the IMS tensioners. Why would one need to lock the engine (cams/crank) ? The chains cant fall off the sprockets, cam or IMS? Or, don't I get it?

Flat6 Innovations

Pulling the tensioner with any cam on lobe will result in loss of valve timing. The chain will often jump, and skip 2-3 rollers.

Don't play with this

cormax

Hi guys, my first post, but my sixth Porsche.

I have a '05 C2S (3.8) which recently started flashing the CEL and gives misfire on all three cyls on Bank1.
I've replaced the easy/cheap suspects (MAF, Spark plugs, coils..) but no change. Still CEL + intermittent misfires on 1,2,3.

Bank 2 has never misfired.
Does not happen when cold (oil thicker...?).
Does not happen when >1000 rpm, only at idle.
So, when warm, idling... it suffers misfires and there is a slight knocking sound detectible from Bank 1 head (this goes away at higher engine speed).
Basically, I can drive all day as long as I don't stop for traffic lights (it may even stall if idling for too long..)

I'm thinking chain tensioners, which is bad enough, I guess... but has anyone actually had continuous misfires at low revs due to slappy tensioners?
I've had the tensioners wear out on an Audi S6 (V8), which gave a very clear noise from the cyl heads, but never misfires on every cyl..

Just interested in your opinions, car is parked while I research how I'm going to deal with this..

Thanks!

ejabour

Any codes? Could be a cam sensor. I don't know what diagnostic equipment you have but it would be helpful to check the cam deviation angle.

cormax

Hi ejabour,

Yes, I read out P300/P301/P302/P303 = Misfires Bank 1 / Misfires Cyl 1 /2 /3 respectively.
Again, If I clear them the CEL will remain off until next time I have to idle.
Performance-wise, it's still quite happy to go, but I have parked it for the moment until I'm sure what's going on.

I should also point out, for what it's worth, that these symptoms only started after I had the transmission out to replace the clutch.
I'm wondering, now that you've put that idea in my head, whether I touched a sensor or it's cable during the rebuild. I guess I should raise it up and crawl under again...

Never had this kind of thing old air-cooled SC : engine and gearbox whipped out in 60 mins flat

Macaero

if you figure this out let us know, I have a 05 997.1 (early) and have the same issue. I have spent close to $2000 just trying to sort it out. it is the only reason I may sell it. I carry a OBDII code reader and clear/go forward. A real PIA

cormax

... Just waiting on parts... will update

cormax

Hi everyone,

It's been a while, but today I swapped out the solenoid valve on bank 1 and started up the 997 3.8.
It ran a little smoother, but after it reached temperature (5 mins) it started to misfire and give errors... so problem not solved.

I then replaced the solenoid actuator and restarted the engine.
Bingo.
Smooth running at stationary.
Immediate reaction to the throttle.
After 15 min of idling and reaching operating temperature the engine stayed stable at about 750 rpm.

The swap out of both solenoids took about 45 minutes.
I didn't remove the silencer (muffler), as I didn't need to in order to remove the heat shield.

I'm really pleased with the results and would advise anyone with rough idling that is not solved by MAF, spark plug or ignition coil replacement to consider the variable cam solenoids as the culprit(s).
For the 997 3.8 the part numbers are :

Actuator : (in order of updates)
- 99610530302
- 99610530303
- 99610530304
- 99610530305

Valve:
99710530100

cormax

I can confirm (see my post further down).
Replaced both cam solenoids on the side in question (bank1) and it turns out to have been the actuator solenoid that was end of life.
An easy (25 mins per solenoid) and relatively inexpensive repair (about $200 for the actuator).
Engine is now idling smoothly and no misfiring.

Thanks for your comment, which steered me in the right direction!

cormax

Just a quick update; A little over a week onwards and the 997 S is running sweetly. I'm still very relieved