Smart Forfour Misfires Point to Intake Manifold Issues

I experienced something very similar with my 2004 Smart Fortwo CDI. These symptoms immediately remind me of my own vacuum leak troubles, which turned out to be a scorched intake manifold. The symptoms you describe, rough running, jerking, and stalling, match exactly what I dealt with. The engine performance was seriously compromised, and the check engine light was a constant reminder something was wrong. After taking it to my regular workshop, diagnostic testing confirmed air intake issues stemming from a damaged manifold. The car manifold had developed leaks due to excessive heat exposure, causing irregular air-fuel mixture and engine misfire problems. The complete repair included: Manifold replacement, New gaskets, Pressure testing, System recalibration Total cost came to 1180€, but it completely resolved the issues. Before offering more specific advice, could you share: Current mileage, Any recent repairs, Whether you notice the problems more during cold starts, If you hear any whistling sounds under acceleration This information would help determine if your case matches what I experienced and could guide you toward the most effective solution.

Just finished checking my diagnostic readings after the latest service 2 weeks ago. The manifold sensor showed irregular voltage patterns similar to yours. Using my scanner, I got error codes P0106 and P0107 pointing towards issues with the intake manifold pressure readings. Interestingly, my vacuum leak symptoms got worse after 193534 KM. The engine performance decline was gradual, starting with occasional misfires before developing into the constant issues you describe. The air intake system definitely needs thorough inspection, especially around the manifold gasket seals. Workshop quote for diagnostics and potential manifold replacement stands at 950€. Might be worth getting a second opinion given the repair complexity and cost.

Thanks for sharing those diagnostic details, the error codes P0106 and P0107 definitely confirm our shared manifold pressure sensor issues. Based on my repair experience, those irregular voltage patterns are a telltale sign of manifold problems in these engines. The 950€ quote actually sounds reasonable compared to what I paid (1180€). The manifold sensor replacement alone was a significant portion of my total cost. Given your mileage is close to when my issues peaked, this repair timing makes sense. A quick tip from my experience: have them pressure test the entire intake system. My mechanic found additional vacuum leaks around the gaskets that werent obvious initially. The complete manifold replacement resolved both the sensor readings and the vacuum issues. Getting a second opinion is smart, but with those specific error codes and matching symptoms, you are likely looking at the same repair I needed. Just ensure they use OEM parts for the manifold sensor, aftermarket sensors caused problems for some forum members with similar issues.

Thanks for the diagnostic code info and mileage details. Really puts things in perspective. My vacuum leak symptoms did follow a similar progression path, started small and got worse over time. After comparing the similarities in our cases, especially those manifold pressure sensor readings and error codes, I am more confident about proceeding with repairs. The gasket leak and intake manifold issues seem nearly identical to what you experienced. The 950€ repair quote feels more reasonable now seeing your final costs. Will definitely request the complete pressure testing you mentioned to catch any additional vacuum leaks around the manifold area. Makes sense to fix everything while they are in there. Still planning to get that second opinion, but your repair experience has been incredibly helpful in understanding what I am dealing with. Will make sure they use proper OEM parts for the manifold sensor replacement. Going to schedule the diagnostic inspection for next week and will update once I know more about the full extent of the repairs needed.