inexperienced (but learning!) Liberty CRD owner here, would really appreciate some advice...

The problem: when I go up a hill, I lose a lot of power and have to creep along at 20-30 mph on the highway. When this happens a lot of thick black exhaust is coming out of the tailpipe. I am also hearing a new "whirring" sound, that kinda sounds like an electrical motor...not sure if that is related to the main issue.

A little history: I bought the Liberty about 8 months ago knowing the EGR valve was not functioning. I saw online that this was a common issue and not really problematic, so I have not fixed it yet. The check engine light has been on the whole time as a result.

This problem first began on a trip I made to the Oregon coast where you can drive 4WD vehicles on the beach. I was driving down the beach no problem but to get off the beach I had to go up a hill through some heavy loose sand. I didn't make it very far before the thick black exhaust came pouring out. I then found an easier exit and got off the beach but got stuck in deep sand at one point and a dune buggy with a winch pulled me out. Ever since that I have experiened the problem and have not been driving much as a result. (side note: I pulled my travel trailer across the country with this Liberty and a couple times experienced similar symptoms when going up steep hills but it was never this bad and always had plenty of power)

Please tell me what you think and advise me on how to troubleshoot this problem in a cost effective way. I really appreciate the help. THANKS!