P0343, woe is me
 

2003 996, 2wd, man trans
here's the run-down, symptoms:

• when fully warmed-up, driving at 2800-ish RPM at light throttle, there is an intermittent surge or jerk, best described as a 'hiccup' felt
• very intermittent hard starting (crank, no start) after a short hot soak, starts on 2nd or 3rd try. Has stalled two or three times at idle, soon after coming off of a long freeway run (but not immediately after)
• has thrown P0343 code a couple of times, after experiencing the 'hiccup' for an extended period (long freeway drive, smooth road), freeze frame data always shows it at 2840RPM
• one time also recorded misfire codes on the opposite bank at the same time as the P0343
• check engine light does not stay on

The camshaft position sensor for bank 1 seems pretty well hidden, but at least I could see there were no signs of rodent activity in the engine bay

Any suggestions or anecdotes?

There is a bracket that holds on the sensor that is a known failure point. it can crack and vibrate. Sounds like it with the intermittent failure.

Might want to get cam deviation checked to be sure nothing more going on.

Do you have service history?

P0343 is bank1 cam sensor shorted to B+. The sensor should be below the alternator. Need to check the wiring of the sensor. No way around that.

So is the sensor located at the "front" of the engine (rear of the vehicle)?
When I try to look it up, I find varying descriptions.
If I'm getting a cam position sensor fault, will my deviation readings be accurate?

Yes, it's the black connector to the right of the green cam plug. I think the DME is smart enough to detect a short and ignore the bad readings. Do you have odd cam deviation readings?

https://cimg0.ibsrv.net/gimg/rennlis...873e9b0281.jpg

Ahhh, I see it in the picture, thanks.
I haven't checked cam deviations yet, will have to fire up the Durametric this weekend

The Variocam+ will give a slight, brief "surge" at about 3100 RPM's. /X3

This is definitely not a variocam surge, it's just below 3000RPM and harsh

I suspect your bank 1 cam sensor is acting up or there's an intermittent short in the wiring. The cam sensor wires go from that connector in the pic to the X59 connector, then to the DME. Not sure why it always happen at the same rpm though.

I'm hoping for it to be the sensor only. Considering how it only acts up when really warmed-up, and driving on a smooth surface...
You'd think if there was a broken wire or connector then rough roads would be a factor.

I was finally able to spend a little time poking around. With the airbox out, I could see the sensor and connector on the driver's side cylinder head. I was able to unplug the connector, and it was "wet" inside. With what, I cannot tell. Next I want to remove the sensor, but haven't figured out how to get a wrench to the allen head bolt holding it in. It seems as if I'll need to support the engine and remove the carrier plate to gain access.

OK, with the help of a stubby 5mm 1/4" drive, I was able to extract the old sensor. It appears to be full of oil. I have a new Bosch sensor going in, we'll see what happens...
https://cimg3.ibsrv.net/gimg/rennlis...67d71b1df8.jpg
https://cimg5.ibsrv.net/gimg/rennlis...a452dbb3c1.jpg

I'd say Sensor has deteriorated and is wicking oil back to wiring connector head, I had similar on my MB, II went ahead and replaced , Later Crankshaft Sensor went, giving same symptoms, intermittent firing after warmed up. replaced. Runs like new.

You may want to use contact cleaner to clean the electrical socket thoroughly before plugging it to the new sensor.