Your IELTS speaking test result was still not satisfactory, while your spoken English is much better than the average, grammar was high in quality, and you are able to express your ideas in a much better way, you have a rich vocabulary and spoke fluently. The reasons behind your failure is you followed tips in a wrong way. Tips that gone misunderstood are:
Tip 1. Don't speak too slowly
This is the most common type for IELTS speaking: speak slowly, not speak like you are running, and communicate in a slow and clear voice without confusing the examiner. But here the main element of the tip is not reducing the speed of the speech, instead speak fluently with a constant average speed. If you speak too slowly or too faster than in that case you'll get a low mark for fluency if you speak slowly in the IELTS speaking test. Try to speak at a normal talking rate instead of an unnaturally slow or fast speed.
Tip 2. Don't worry too much about pronunciation
Many candidates believe that their first language accent while speaking English will fetch them low marks in the test. In fact, having an accent is not a problem. It's possible for you to speak with a foreign accent and still get a high mark for pronunciation. Even if you occasionally pronounce a word incorrectly, you can still get a band score that's good enough for entry to most university courses or for migration to another country.
Tip 3. Don't use only simple words
The main objective of the speaking test is to evaluate your ability to communicate efficiently in spoken English. The examiner at IELTS test will definitely look for is whether you have the words to talk about known and unknown topics. The examiner also evaluates whether your vocabulary is good enough to talk at a stretch on topics without employing the similar words while whole test. There is provision to give separate marks for vocabulary in IELTS speaking test. You will get more marks if you have a wide range of vocabulary which you can use appropriately.
Thus, the idea here is you should try hard to show your knowledge and expertise in English. Try to show the high range of words you have to present your idea. Try to use less commonly used words, phrases and idioms, but use them in a correct way. This tip will surely help you in getting more marks.
So, follow all these advices like, speak at a normal speed; don't worry about pronunciation; use some high-level vocabulary; use lengthy sentences; and give full answers when appropriate for better marks.
