Hi, welcome to jA.
Alright, thanks for the info. We recieve 3-4 gasoline vehicle's which received diesel, a month. I have had this occur on Rav4's before...it really isn't a big deal, you simply drain the gas tank, replace the fuel filter, and we normally run the engine on a injection machine (gasoline) prior to letting it run on it's own again. I doub't any real damage could have occured, with such low milage. At our facility we charge 2.0 hours (approx $180) to repair this condition. I'm confused as to why the dealer is having such a difficult time, unless they're not familiar with this occurance, or they're trying to sell you more than what you need. It's also possible they didn't completely drain the diesel, even if one gallon was left in the tank and they added 2 gallons or so after the cleanup, well the dillution is still not enough to properly run a gas enigne, so ask how much they added after. Or it may be that after driving it 20 miles, another coincidental problem arrose. Find out for me what is occuring now, does the engine crank and not fire, does it not crank, does it fire and run bad, does the check enigne light come on, etc...this will give me a better idea on if something new has occured after the fact.
So, i'm a little confused becuase I wonder how the dealer came to the conclusion that Diesel was in the fuel tank. If this occured once the gasoline was used up in the tank (Diesel floats on fuel) the engine would stall, and you couldn't drive it. So this Diesel scenario doesn't make sense (unless someone added Diesel or another substance to your fuel tank). Now, these have common problems for stalling such as the IAC (Idle Air Control) valve, but it is not accompanied by a Check Engine Lamp. The Check Engine Lamp illumination is the key to what is going on, do you have any diagnostic codes they retrieved while working on your vehicle? Codes can help me better understand what the engine's computer is seeing. Also, this can be a computer re-flash concern, but the dealer should already know this?? The one item that does make sense is a bad battery. A shorted battery can let the vehicle drive and start normally, than cause intermittent issues such as stalling, becuase the engine's computer is sensitive to power surges, and voltage drops. Has the battery been replaced yet? What did the dealer do for $900, it sounds like they don't know what they're doing, which is uncommon practices of a dealer.
If the battery was of an inferrior brand/quality...it can pose a problem as well. Many of these AutoZone, Pepboys, Advanced Auto, etc they're batteries can cause these problems, or if the cables weren't tightened it can do this as well. And most good technicians will overlook something as simple as a battery, or loose cables. Your Rav4 has got very low milage to be having this problem out of the blue. Thanks for the second accpet, but let me know what goes on, and if your having difficulty with the dealer; even though the insurance co. has made the payment your entittled to a repaired vehicle, and i'm sure the insurance would hate to know it's still not repaired. Also, the dealer should be paying for a rental by now.