We don't know.
However, the evidence suggests that Type 42 really did collide with an object and fall to pieces at the critical moment, and that this was not on purpose. The bad timing and unreliability of the suit is a repeated theme of the movie:
- The suit failed to assemble safely at Tony's workshop prompting Jarvis' sardonic remark 'Always a pleasure watching you work, sir'
- Various systems (notably flight and some weapons) of the Type 42 were unavailable during the Mandarin's attack on Stark's residence
- When Stark was tied to a metal frame by the Mandarin's henchmen he repeatedly summoned the Type 42 before it eventually arrived
- Type 42 was smashed apart by an unsighted collision with a lorry after the Air Force 1 rescue
The narrative evidence suggests that Type 42 did indeed fail at the critical moment once again; yet Stark improvised with a more effective strategy than confronting Killian once again in a suit. Stark only got away with this because Killian politely (and overconfidently) waited for Stark to reset himself - rather than finishing him off as Type 42 hove into view.