Alfa Engine Stalls: Key Signs of Fuel Regulator Failure

Had a similar issue with my 2008 Alfa 156 2.2 JTS. With some experience working on fuel system issues, I can relate to these symptoms, especially the rough idle and power loss combined with the check engine light. Took it to my regular workshop when the problem started. They diagnosed it initially as a fuel pressure regulator issue, but it turned out the fault code was triggered by a recent fuel filter change. The fuel rail pressure was inconsistent due to improper bleeding of the system after the filter replacement. The fix was straightforward, proper bleeding of the fuel system and resetting the engine management system. Total cost was 45 Euro and took about an hour. The check engine light cleared and the rough idle disappeared completely. Before suggesting more specific solutions, could you share: Current mileage on your 159? When was the last fuel filter change done? Are you getting any specific error codes? Does the problem get worse when the engine is warm? This info would help determine if your issue matches what I experienced or if it might be something else in the fuel delivery system.

This problem started shortly after my last service at 76878 KM. After checking the suggestions, I can confirm the engine misfire gets worse when warm. The rough idle is most noticeable during morning starts. My mechanic pulled code P0171 which points to a lean fuel mixture. The fuel pump seems to be working as I can hear it prime when turning the key. Based on the feedback, I will have the fuel rail pressure tested first before replacing parts. Thanks for the input regarding the bleeding procedure, will make sure this is properly done if any fuel system work is needed.

Your symptoms with the P0171 code match exactly what I dealt with on my 156. After getting the fuel rail pressure tested, we discovered that the pressure sensor and fuel pressure regulator were both contributing to the lean mixture problem. The rough idle during cold starts was a clear indicator, and like yours, my issues got worse as the engine warmed up. The fuel pump was also working fine in my case, but the fuel pressure regulator wasnt maintaining proper pressure across different operating conditions. The complete fix involved: Replacing the fuel pressure regulator (180 Euro), Installing a new pressure sensor (95 Euro), Full system bleeding procedure After the repair, the lean condition cleared up completely. The engine returned to smooth idle, and power delivery became consistent again. My mechanic mentioned that when these components start failing, they often deteriorate gradually, which explains why the symptoms get worse with heat. One tip: make sure they check the fuel pressure at both cold and hot running temperatures. This helped identify the failing components in my case, as the readings were inconsistent between cold and hot operation.

The diagnostic process is starting to make more sense now. Thanks for sharing that detailed experience, especially about checking fuel pressure at different temperatures. My mechanic has scheduled the pressure testing for tomorrow morning, and based on your feedback, Ill make sure they test both cold and hot conditions to get a complete picture. My case seems very similar to yours with the lean condition and temperature-dependent symptoms. Good to know both the pressure regulator and sensor might need attention, will budget around 275 Euro for parts just in case. The investment seems worth it to resolve these fuel efficiency issues and clear that persistent check engine light. Interesting point about the gradual deterioration pattern. Looking back, I did notice slight power drops over the past few months before the major symptoms appeared. Will update the forum once we confirm whether the fuel pressure regulator is the root cause and complete the repair.