An odd thing happened two days ago. We had single-digit weather, and my car was outside for a large majority of it. Upon starting it, I noticed that the idle was bouncing from 1000 RPM to close to 400. As I drove, power felt intermittent, and each time I put my foot on the clutch, the revs would drop to 400, rev up to 600-800, and repeat.
After 3 duty cycles, the SES came on:
Code:
P112F
Description:
Throttle-valve angle - intake-manifold pressure, correlation: Limit value exceeded
People-friendly description:
The fault is recognized when the relationship between the indicated intake manifold pressure and the mass airflow calculated based on throttle-valve angle is not correct.
The next day, temperatures went up to a Florida-like 26 degrees. When I started the car, it idled and drove as if nothing was wrong. The temperature has been slowly climbing, and the symptoms have not come back since.
Common fixes:- Check intake system and crankcase for leakage
- Check throttle valve (contamination, carbon deposits, icing)
- Check plug and wiring harness between intake manifold pressure sensor and DME
- Check plug, wiring harness at electric throttle valve actuator
- Replace pressure sensor
- Replace throttle valve
Two things have been done in the recent past (~3 weeks ago):
1. VANOS Recall
2. Oil change
The two possibilities I am thinking are:
1. Since it only occurred during extremely cold weather, icing causing the throttle valve to stick is very plausible
2. The VANOS recall involves removing the valve cover, meaning things like the intake and crankcase vent connections are removed. I noticed that the left-side rubber intake boot was ever-o-slightly not flush. I corrected this, but it did not seem to make any air leaks. Note that this is an aFe sealed intake, and not stock.
I did not see anything awry on the valve cover, albeit there were oil stains coming from the oil cap. They did not look fresh, so I am guessing that it occurred during the oil change. Maybe someone spilled something and did not notice it. The cap does not appear to be leaking, but I will clean it and check later. I did not have any leaks in this area prior to having the recall and oil change done.
I'm hesitant to take it to the dealer for reasons of them saying something like it's unrelated to the VANOS recall, and then charging me a diagnostic fee...though, I am under CPO I'm more likely to believe it has to do with the cold weather and icing.
What are your thoughts on this, before I ask the dealer to look at it in case they made a mistake?