Got a customer with twin 6.2 mx mpi motors. When engine is cold if you rev it up and drop throttle down to idle the engine will stall. Has new IAC also. When engine is warm the problem is not there. Sound like a bad temp sensor? let me know guys thanks..

I had different behavior, but had to replace the cap + rotor right off the bat on my 2002 6.2. Maybe something just to check?

Check for carbon build up around and in the throttle body. If there do not use carb cleaner, simple green or throttle body cleaner. Reason is there is a gap to allow air to pass even when closed, if carbon builds up air can't pass.

Both engines, or just one. Could be gas. Swap the sensors. What about the map sensor. How is it when it revs, is it smooth. Did you try running a few cans of sea foam through the tank. Check for vacuum leaks too. Might want to smoke test the intake. Just some thoughts ��

Just one engine . Just repowered a customers boat do to elbow gasket failure . The old engine had this problem and I could never figure it out. Boat runs great once warmed up. When cold you can't rev it them slam the throttle back to idle with out it trying to stall. Weird . The engine has no problem idling on its own though.