gurpreetsingh, "try repairing" as for every form " Try + gerund" means experimenting with something. However try + infinitive conveys intent and purpose.
For example:
-"I will try learning this concept" = I will get my hands dirty to learn this concept (not sure will succeed, though)
- "I will try to learn this concept" = I will purposefully strive to learn this concept
In the sentence, I doubt the sentence is "experimenting". Rather, the author's intent is to repair and really do that, rather than junk the car.
The other issues in the sentence are parallelism-related. Only Infinitives are parallel to each other. We should not mix simple gerunds with working verbs, nor with infinitives.
In "try repairing..have it junked" - besides any concision issue, we are paralleling here gerund (repairing) with a noun modified by a past participle (noun modifier). Again this is not structurally parallel.