Grammar still becomes one, among other factors, that contributes a serious problem for students to write in EFL classes but which component is said to be the cause needs a careful study. This article is written to identify the components that trouble them the most and to find out ways of solution. In this article, eight grammatical components were identified, including (1) consistency of subject and verb tenses,(2) consistency of singular and plural nouns,(3) parallel construction,(4) tautologies and redundancies,(5) misplaced modifiers,(6) faulty references,(7) passive construction,(8) choice of verb forms. Data were collected from students’ free writing. For this purpose, they were asked to write essays before and after feedbacks were given. The feedbacks consisted of various class activities, such as formative tests, peer reviews, teacher notes, and class discussion. Using dependent paired t-test, scores from both writing tasks were compared to see the difference. In addition to such quantitative computation, a qualitative analysis was also made to find out reasons how and why students encountered grammatical problems in writing. The research reveals the findings, such as (1) all respondents encounter problems about the eight identified grammatical components; two of which are severe,(2) frequencies of such arising problems vary from one student to another,(3) interference of native language, Indonesian grammar, is suspected to be the contributing factors to affect students’ quality writing,(4) individual feedback and classroom discussions turn out to be an effective way to improve students’ writing,(5) there is significantly different achievement of students in writing before and after feedback.