JanosP

Hi everybody!

So my 4S looses power a little over 6.000 rpm with an occasional judder, accompanied by a little puff of white smoke (noticed from another car). The engine light comes on for about 10 seconds.

There was a 637 fault code (valve lift control checksum error) and 627 (valve lift control cylinder 1), misfires on one bank (4-6), checked the cam deviation (-1,11 position 1 and -7,28 position 2). We replaced the tensioners and the deviation dropped to -0,48 on position 1 and -6,55 on position 2, the valve fault codes don't come on anymore, the misfire number also dropped.

So where do I go from here? My mechanic thinks these are two separate problems and wants to change an injector on one cylinder. What about the camshaft dev? Change the pads on one side? It's a bit frustrating because I had the engine out last year immediately when I bought the car and my mechanic and I failed to notice the issue beforehand (he works with 911's but is not a proper Porsche specialist).

I know this is something that has been talked about a lot on this forum already, but anyway, I'd like to engage a bit and maybe get to know a bit more about my car in the process . Many thanks for the answers!

pdxmotorhead

I personally would change all 6 injectors or they are all the same age and generally injectors have pretty even wear.
You could also have bad coils (Again age related)

To change 1 injector you have to pull a fair amount of parts, by the time you're there getting the other intake out is just not that big of a deal.
basically the labor is where the money is at, LN engineering sells the injectors, there is no free lunch on 996 injectors.. Pay to play..
There are multiple tasks that are enough work to start that the "while your there" can make sense for the long game.

One of the good reasons to run top end lube like Techron/Seafoam at least once between oil changes.. Helps keep the injectors free and clean.

De Jeeper

What year car/motor?

JanosP

It's a 2003 Carrera 4S.

JanosP

So, time to finally solve this problem. Just did a short drive with the OBD connected again. The misfires happened under full acceleration in second gear, and only on one cylinder this time. No misfires when accelerating slowly or just revving stationary to 7000 rpm.

I'm starting to think this is not only camshaft deviation related (7,14 on one side and 1,11 on the other today). The coils are fairly new, so this leaves me with the injectors.

yelcab

What have you done to the bank where the deviation is 7.14 degrees?

JanosP

Nothing yet , but I don't know what was going on before my ownership.

ZuffenZeus

Personally, I would check for cylinder bore scoring on bank#2 before I'd dump anymore money into this engine.

wdb

I'd also check to see what engine mounts and transmission mounts it has. There are reports that some of the stiff mounts cause misfire codes and pulled timing.