On vehicles with a variable catalytic converter, leaks in the exhaust system before the lambda probe can lead to difficulty starting the engine. Engine stalls, runs erratically at idle, «chokes» during acceleration.
Test conditions: engine cold or slightly warm.
Start the engine and check the exhaust system for tightness by plugging the exhaust pipe with a rag. In this case, the assistant should check all joints and flanges for tightness (hissing sounds and exhaust escaping felt by hand).
Apply leak detection fluid to the cylinder head/exhaust manifold and exhaust manifold/exhaust pipe connections and check for bubbles.
Eliminate leaks.