2006 Jeep Liberty

Engine Performance problem
2006 Jeep Liberty 6 cyl Four Wheel Drive Automatic 47000 miles

The engine light comes on periodically and the engine " stumbles" and sputters, hesitating for a while. Was in shop twice for the problem. First time they could not replicate it and felt it was a gas problem. The second time the electronics system diagnosis was " multiple misfires". They deemed it necessary to R& R intake valves and keepers, grind exhaust valves and lapped. Also removed squirrel debris from airbox and intake. Very expensive. This was in February. Now exactly the same thing is happening- sputtering, stumbling and engine light.
Any idea what is really going on?
April 6, 2010.

The vehicle must have sat fopr a while for squirels to start to make a nest. What it sounds like is a sensor. Have they scanned it lately since they did all the work? Try this, get a can of throttle body cleaner and use as directed. There may be a small piece of carbon messing up the sensor. I had what you described to a subaru. My own sprayed the throttle body cleaner in then let it sit for a few minutes. Then started it and let it run for a while. Then I repeated to spray it again. The light stayed off and the engine ran better with better gas millage.

Apr 7, 2010.