Cadillac CTS Power Loss + Black Smoke: EGR Guide

Had similar issues on a 2016 Cadillac ATS with the 3.6L engine. The symptoms matched exactly, rough idle, significant power loss during acceleration, and increased fuel consumption. The check engine light triggered due to improper exhaust gas recirculation. The EGR valve was indeed the culprit, completely stuck in the open position due to carbon buildup. This allowed excessive exhaust gases back into the intake, causing the erratic performance and black smoke. The hissing sound typically indicates a vacuum leak around the EGR system. This is a serious issue requiring immediate attention as it can damage other engine components if left unchecked. The repair involved removing the EGR valve, cleaning the passages, and replacing the valve assembly since it was beyond salvaging. The carbon deposits had also affected surrounding components. After the automotive repair, the engine returned to smooth operation with normal fuel consumption. Would recommend having a complete diagnostic check, as carbon buildup can affect multiple systems. The mechanic should also verify the intake manifold condition since EGR issues often impact this component. Worth noting the repair requires specialized tools and proper diagnostic equipment to ensure all related systems are functioning correctly after the fix.

Thanks for sharing your experience with the EGR valve issue. Really helpful since my CTS showed almost identical symptoms. My repair is scheduled for next week. The vehicle emissions problem has gotten worse and the rough idle is really starting to worry me. Did you remember roughly how much the complete repair cost? Also curious if you had any related issues pop up in the months after the fix? Want to make sure I budget properly and know what to watch out for going forward.

Good news, I got the EGR valve replaced last month and the repair completely resolved all those issues. The total cost came to 355€ for parts and labor, which included cleaning the entire exhaust gas recirculation system and surrounding components. Since the fix, my Cadillac runs perfectly smooth again with no check engine lights or performance problems. The rough idle disappeared completely, and fuel economy returned to normal. No vacuum leaks or unusual sounds anymore either. The automotive repair shop did a thorough job checking connected systems to ensure there were no lingering issues. Three months later, everything is still working great with no related problems. Just make sure your mechanic performs a complete diagnostic check of the intake system while they have it open. The carbon buildup that causes EGR valve failure can affect other components too. The vehicle emissions are now back to normal levels and the engine runs noticeably cleaner. For preventive maintenance, consider having the EGR system checked during regular service intervals to catch any carbon buildup early.

Thanks everyone for the advice. Just got back from the repair shop and wanted to share my experience. The catalytic converter actually needed cleaning too, but thankfully the EGR valve replacement fixed most issues. Total repair came to 420€, bit more than expected but worth every cent. The mechanic showed me the old valve, completely gunked up with carbon. They cleaned out the whole system while it was open. The difference in performance is incredible. No more rough idle, black smoke, or that annoying hissing from the vacuum leak. Fuel consumption dropped back to normal too. The check engine light is finally off after weeks of worry. Really glad I got this sorted before it caused more damage. Engine runs smooth as new now. Going to keep up with regular maintenance to prevent this happening again.