Its always good to help, but don't encourage the poor bloke to diagnose by parts changing/guessing.
Put a scan tool on it. Find out if there are any sensor problems on the engine. GTS Boy gave you the correct answer.
When diagnostic ports were first appearing in cars, Big Bob (our workshop foreman) would march any apprentice down the workshop by his left ear to the Diagnostics Trolley if he found he had not run Diagnostics before hoisting the vehicle. Early Diagnostics units cost the same as a small car, BIg Bob took the price personally.
(Apologies to any new age men out there, this was called learning by example in the old days.)