Hi. I have a 1999 C2. I recently took the engine out to replace Vario-Cam pads along with the other "while you're in there" stuff(AOS, clutch, water pump, thermostat...). Several times since then I have gotten a P1123 code. I reset the light and things will be fine for hundreds of miles. Then a repeat of the same.

My OBD2 scanner gives me freeze frame info from the time the code was set. It shows that it was set at idle and -22 LTFT on both banks. It seems to be running this "high negative trim" at idle all of the time. I have researched the P1123 code and am aware of the usual suspects (MAF, leaking injector, high fuel pressure). I have checked the fuel pressure, which is fine.

I also have durametric from which I have baseline data from before this issue began. What jumps out is that now my TRA on both banks is now .3, whereas it used to be slightly negative. I see in the WSM that this rise in TRA is also associated with removing the oil cap. I have a manometer and plan to get crankcase pressure readings later today. Perhaps my new AOS is defective?

I find it noteworthy that the OBD2 LTFT seem to be cutting fuel while the TRA read from durametric seem to be adding fuel. Durametric doesn't show me the post cat o2 sensors or freeze frame data, which the OBD2 scanner shows. I would think all of the OBD2 data would be included in the Durametric data.

Any insight would be appreciated.

Thanks,
Edward

 

I've checked the crankcase pressure and it is 0.3 inH20 vacuum. I understand it should be around 5 inches.

 

According to your Tra and FRA and manometer reading you are running very lean from a large crankcase leak../

OBDII fuel trims are wonky and don't follow Porsche tester logic, so I rarely use them...

Since you have a 99 check the rubber bellows under the AOS and the oil fill tube for big cracks...Also any AOS tubing..

Anything else will also leak oil as an indicator ( like the rubber cam plugs ect.)...