Rough Idle & Heavy Fuel Use Points to Faulty Sensor

Had similar car problems on a Chrysler 300C 2004. The symptoms you describe, poor performance, rough idle, and high fuel consumption, along with the check engine light point toward ignition timing issues rather than just a knock sensor. The knock sensor helps prevent engine damage, but these symptoms often indicate a more comprehensive issue with the ignition system. In my case, it turned out the ignition coil pack had failing connections and corroded terminals. The repair required replacing the entire coil pack assembly and checking all related wiring harnesses. This is a serious repair that needs proper diagnostic equipment to verify. Ask the mechanic to: 1. Perform a complete diagnostic scan, not just read the check engine codes 2. Test the ignition coil resistance values 3. Check fuel pressure and injector signals 4. Verify timing chain tension Watch for signs the mechanic is just guessing, they should be able to show you test results and explain exactly why they believe specific components need replacement. A proper diagnosis will involve testing multiple systems since these symptoms can have various root causes. Make sure they document all findings and verify the repair solved all symptoms before accepting the job as complete.

Thanks for sharing those details about the ignition system issue. That definitely sounds like what I am dealing with too. The malfunction indicator light symptoms match perfectly. Just wondering, what did that coil pack replacement end up costing you? And has everything been running smoothly since the repair? My Crossfire has been a great car otherwise, just concerned about getting this engine knock and timing issue resolved properly with a competent mechanic this time around.

Since getting it fixed, my 300C has been running perfectly with no engine knock or warning lights. The mechanic found the actual problem was just a loose knock sensor connection causing incorrect ignition timing, much simpler than the full coil pack replacement I initially thought was needed. The fix only cost 95€ to repair the wiring connection on the knock sensor. The malfunction indicator light cleared immediately after the repair, and fuel consumption returned to normal. Really glad it turned out to be a straightforward sensor issue rather than major ignition system work. Make sure your mechanic thoroughly checks the knock sensor connections first before jumping to replace more expensive components. A proper diagnostic scan should pinpoint if you have the same simple wiring issue I had.

The advice about checking the knock sensor connections first really helped. I took my Crossfire to a new mechanic who actually listened when I mentioned the symptoms and your suggestion. After running proper diagnostics, they found almost the exact same issue, a damaged wire harness near the knock sensor that was causing erratic ignition timing. The total repair came to 120€ including diagnostic time. The check engine light cleared up right away and the engine runs smooth again. No more rough idle or excess fuel consumption. Such a relief it was just a wiring fix and not a major engine problem. Really glad I got a second opinion instead of going back to the previous mechanic. The new shop showed me exactly what was wrong and fixed only what was needed. Car has been running great for the past few weeks with no warning lights or poor performance issues.