mocne

I bought my 996 about 3 years ago and it came with a P1539 code. Other issues at the start of ownership were a noise only heard at idle that was rhythmic in nature (later found to be a loose plug on bank 2) and chain tensioner noise on startup. A first oil analysis found no issues.

Almost immediately I took it to an old-school Porsche mechanic because I didnt trust myself working on the car but at the same time I wasn't sure how much he knew about the newer cars. Instead of troubleshooting we decided to do the spark plugs, spark plug tube seals, EPS IMS (Dual-row with 92k miles was perfect!), EPS RMS, clutch, cam tensioner pads and chains, and the AOS. I was allowed to help which was amazing and I learned quite a bit but unfortunately when the car was all back together I still had a P1539 code. I didnt have time to troubleshoot it much in the bay so I replaced the most probable part, the solenoid.

I didnt drive much since them, maybe 1k miles out of fear of damaging something, fast forward to today and I found that the P1539 was due to a transistor being burnt in the ECU, I replaced this and now I no longer have that code. I assume the Variocam is now working correctly because if I trigger with my Durametric either of the banks I get the car to stall out.

Currently and before the P1539 fix I have had rough idle when warm since the extensive work outlined before, I thought perhaps fixing the Variocam system could potentially influence the idle, but so far it remains the same. I dont remember if it was a problem before the work because I drove it so little at the time of purchase.

So where should I start to look now? Car runs well at speed. At idle, when warm the car runs rough, it constantly seems to be compensating for something. Bank 2 in layman's terms seems to be coughing and you can hear valve train noise from there, Bank 1 seems to be smoother. I can remove the oil cap when the car is running and you can hear the air getting sucked in. I have looked for loose vacuum lines. I have disconnected the MAF and I didnt really notice any changes. I cleaned the MAF since the car has a CAI.

Another detail that may help, when we did the chains and cam pads, the engine was locked at the crankshaft and a cam tool locked the cams and the tensioners were removed, but when we put it back together we did not rotate the engine and check any of the timing.
Could the timing be slightly off on Bank 2 where I hear the valvetrain noise?
Could it be the Variocam actuator be a bit sticky since it wasn't used all this time?
Could there be some sealant blocking the oil galleys causing some of this noise? It feels like the noise and idle issues on Bank 2 could be related but I'm not entirely sure. On a cold engine I cant hear any valvetrain noise, so maybe lubrication could be an issue too?
Also when installing the engine I pinched the fuel line leading to Bank 2, could this be causing some issues with fuel delivery?
Sorry for the long post, I felt that more information could help. Hopefully someone could point me at what to look for in Durametric to help diagnose the issue. I'm including an Excel spreadsheet of some of the actual values from a drive and from sitting in the driveway.

Thank You!

ltusler

Have a look at the idle control valve on the left side of the TB, they tend to get dirty and stick.

mocne

Update, I cleaned out idle control valve, it was dirty but this didnt influence the idle issue when warm.

What did fix it was replacement of the ignition coils - now she purrs. No codes were ever given but some were cracked.

Thanks!

Noz1974

Have a look at the oil filler tube , it can crack across one of the flexible ribs and not be very noticeable but will be sucking air in, I had that on my 1999 3.4 , I also had a bad solenoid on one bank but it sounds like yours are ok if your stalling out on both banks with the durametric , if it's not the variocam it's usually an air leak somewhere, the oil vent lines break aswel and can cause problems , they are not easy to change either , maybe do a smoke test ?