Alfa 147 JTD Power Loss: Intake Manifold Warning Signs

Had almost the exact same issue with my Alfa 156 1.9 JTD from a slightly older build year. As someone with some hands-on experience working on diesel engines, those symptoms immediately point to intake manifold issues. The manifold pressure sensor was giving incorrect readings, and there was a significant gasket leak where the manifold connects to the cylinder head. The scorching around the gasket area made it impossible to just clean and reseal, complete manifold replacement was necessary to restore proper engine performance. The workshop found carbon buildup and heat damage had warped the original manifold slightly. They replaced the entire intake manifold assembly, all gaskets, and the manifold sensor. Total repair cost was 1180 Euro including parts and labor. The fix completely resolved the power loss, rough idle, and stalling. Engine performance returned to normal and the check engine light cleared after the repair. Could you share: Current mileage on your 147? When did the symptoms first appear? Have you noticed any black smoke from the exhaust? What error code is stored? This information would help determine if your issue matches what I experienced and whether cleaning might work or if replacement is needed.

Thanks for sharing your similar experience. My 147 has 116296 KM on the clock, with the last major service done 6 months ago. After inspecting more closely, I found traces of what might be a vacuum leak around the manifold gasket area. The air intake system seems to be compromised, leading to these engine performance issues. The misfire symptoms and rough running get worse when the engine is warm. The stored error code is P0401, EGR Flow Insufficient. Havent noticed black smoke, but the diesel smell is quite strong, especially during idle. I will probably have to go with a complete manifold replacement rather than just cleaning, based on your experience. The car manifold seems too deteriorated for a simple fix.

Thanks for providing those additional details. The P0401 code matches exactly what I experienced before the manifold replacement on my Alfa, and the mileage is also in a similar range where these issues typically develop. The strong diesel smell combined with the EGR flow code strongly suggests restricted flow in the intake manifold system. On my 156, the manifold deterioration was causing improper air-fuel mixture, leading to engine misfire and the same performance issues you describe. A crucial detail you mentioned is the symptoms worsening when warm, this was also the case with my car. The heat cycling causes the warped manifold to expand differently, making the vacuum leak more pronounced and affecting engine performance even more. Given the similar pattern of symptoms and the visible traces of vacuum leaks, I would strongly advise against just cleaning. From my repair experience, once the manifold gasket area shows deterioration, a complete replacement of the intake manifold assembly including new gaskets and manifold sensor is the only reliable fix. Have you noticed if the check engine light flickers or stays constant? On my car, it would occasionally flicker during acceleration before staying permanently on, which was another telltale sign of the failing manifold system.

I appreciate all the detailed information. The check engine light stays constant except during hard acceleration when it sometimes flickers. This matches what you described perfectly and confirms my suspicions about the manifold. Based on the similar symptoms, error codes, and especially your point about heat cycling making it worse, I am now convinced I need a complete intake manifold replacement rather than attempting any temporary fixes. The vacuum leak and EGR flow issues are clearly affecting engine performance in the same way you experienced. I will schedule an appointment with my workshop and request they replace the entire manifold assembly including all gaskets and the manifold sensor. The quoted 1180 Euro repair cost seems reasonable given the amount of work involved. The fact that your repair completely resolved the diesel smell, rough running, and power issues gives me confidence this is the right approach. Better to fix it properly now before the compromised car manifold causes additional engine damage or leaves me stranded somewhere. Thanks for the thorough explanations, this helped narrow down the problem and avoid wasting time with partial solutions that likely would not have worked long term.