Chrysler Repair: My car wont start, lean mixture, egr valve

Question
Hi Kevin,
I have a 1997 Sebring Convertible.  I have had no problems up until now.  Problems started when I hit a manhole and broke an axle.  Since then my car would randomly slam into safe mode.  I took it to two mechanics and they got an underdrive fault reading in the selinoid pack.  But they could not be confident that this was actually the problem and they didn't want to add it then take it off again if it wasn't fixed.  All other electrical tested fine.  Well, 2 days ago, after many fits of limp mode, pull over, turn off, turn on and drive, my car left me in the street dead.  It was turning over but it wasn't catching.  Towed it to the shop and 2 days later both the mechanic and Chrysler are now confused as to why this won't start.  No new codes were found, just the underdrive.  But again, they are not sure about it.  One reason why they are not confident is that the pack looks like it has been replaced in the last year.  It's practically new.  It's getting gas, there is a spark, the tranny's turning,  they just don't know.  When she died, she was throwing a safe mode fit and it felt like someone was pulling backwards on my car.  It took everything just to get it to the side of the road.

My dad says the it could be the wiring harness in the main computer.  Is this possible?

Also, while my Hubby was cleaning out the air filter, there was acorns under the filter at the bottom of the compartment there. I don't know how they got in there as the car doesn't sit long enough for a squirrel to set up shop.  Is it possible that some acorn pieces(some were broken and eaten)  got into the engine itself?

Sorry for such a long question.  I love this car and I can't understand why even my mechanic can't find the issue.
Thanks Mandy

Answer
Hi Mandy,
About the only item that might very well produce a no start with both gas and spark and no codes is if the egr valve is stuck slightly ajar. That will cause a too lean mixture to allow it to 'catch' and idle. So if the shop wants to inspect the egr valve, move the valve stem back and forth with the tip of a screwdriver, lubricate it where the stem enters the valve, and then make sure the stem closes to a dead stop with the help of spring-action, then try to start it. It might just spring to life. I can tell you more details if you want to try this yourself.
Sorry for the delay but I just found the question in the 'pool' to which Kevin had referred it.
Roland
PS Please 'rate' my answer, and where you see the question about a nomination of me to be "volunteer" of the month consider responding 'yes'. Thank you