Vrombir is a french second group verb. So it follow the regular conjugation pattern of the second group like: 
finir. Follow this link to see all the endings of the conjugation of the second group verbs : 
conjugation rules and endings for the second group verbs.
																												
																												Vrombir is conjugated the same way that verbs that end in : 
-ir.
																												The prototypical verb for the second conjugation is 
finir. The conjugation is, marked by the vowel 
i and the infix 
-iss- in the indicative present and imperfect.																												
																																																																																																		
Vrombir verb is conjugated in negative form. The placement of the negative adverb follow the following rules:
									
 - the adverb 
« ne » is placed after the pronoun and before the verb.
									
 - in simple tenses, the adverbs (
« ne ...pas », 
« ne...plus », 
« ne...jamais », etc...) surround the verb 
vrombir.
									
 - in compound tenses or in passive voice, the negative adverbs surround the auxiliary.