Q5 Cold Start Issues & Heavy Fuel Drain, Fix Needed

Had identical symptoms on a 2011 Audi A4 2.0 TSI last winter. The PTC heater failure caused similar issues, rough cold starts and excessive fuel consumption. The heating system would struggle, making the engine compensate by running rich mixture until reaching operating temperature. The temperature control unit was malfunctioning, preventing the heating element from properly engaging during cold starts. This caused the engine management to adjust fuel mixture incorrectly. The diagnostic showed the auxiliary electric heater had failed completely. The repair required replacing the complete PTC heater assembly and reprogramming the heating system control module. This was not a quick fix, the components are tucked behind the dashboard requiring significant disassembly. The cold air issues and rough running disappeared completely after repair. This is typically a serious problem that should be addressed promptly, as continued operation can impact engine components and fuel system. The symptoms match exactly what you describe, the engine trying to compensate for lack of proper heating during cold starts by running rich. Would strongly suggest having it diagnosed at an authorized service center, as proper diagnostic equipment is needed to verify PTC heater operation and programming.

Thanks for sharing your experience with the PTC heater issues. My Q5 had the exact same symptoms last year, really rough when cold and the heat not working properly until fully warmed up. The blower motor would just push cold air at first. The diagnostic confirmed failed heating elements in the PTC unit. Fixed it about 6 months ago and the cold start problems disappeared completely. The fuel consumption went back to normal too. Just wondering, do you remember roughly what you paid for the complete repair? Also curious if youve had any other heating system issues pop up since getting it fixed? Trying to understand if this is usually a one-time fix or if other related problems tend to develop later.

Really glad I could help identify the PTC heater problem. Had the repair done at a certified shop and the total came to 350 Euro for replacing the defective electric auxiliary heater. The HVAC system has worked flawlessly since, no more cold air issues or rough running during startup. The blower motor delivers proper warm air right from the start now, and cold weather performance is back to normal. In my experience, once the heater repair is done correctly, it tends to be a permanent fix. Have not had any heating-related problems in the 18 months since the repair. The improved fuel economy alone made it worth fixing, the engine no longer needs to compensate for the faulty heating system during cold starts. If the repair is done with quality parts and proper programming, these auxiliary heaters usually last the remaining life of the vehicle.

Thanks everyone for the great advice. Finally took my Q5 to a different mechanic last week, what a difference proper diagnosis makes. The electrical fault was exactly in the PTC heater like suspected. The whole repair took about 4 hours. They had to remove quite a bit of the dashboard to access the heating element and blower motor assembly. Total bill came to 420 Euro including parts and labor. Car runs perfectly now, no more cold start issues or excessive fuel consumption. The heater kicks in right away and cabin warms up quickly. Such a relief to have it fixed properly. The shop explained these heaters usually last the life of the car when replaced with genuine parts. They also did a full system check to make sure there were no other underlying problems. Money well spent compared to the previous botched repair attempt. Really appreciate all the detailed responses that helped confirm my suspicions about the PTC heater being the culprit. Saved me from another potentially bad repair experience.