With the series already decided 2-0 in favour of Pakistan, India were expected to play for pride. But the Indian top order failed once again after skipper Mahendra Singh Dhoni opted to bat on a chilly afternoon.
Dhoni, who was a doubtful includion because of a sore back, once again top scored with 36 while Suresh Raina made 31.
Ajmal suffocated the middle-order after a fine opening spell by Pakistani pacers, Junaid Khan (1/17) and Mohammed Irfan (2/28).
For Ajmal it was his second fifer - the first (5/43) coming against England in Abu Dhabi last year.
With Sehwag dropped, India started with Ajinkya Rahane and Gautam Gambhir but the pair flopped.
Irfan was the first to strike by removing the two openers. He lured Rahane (4) into a drive and a faint edge carried on to wicketkeeper Kamran Akmal.
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Gambhir's poor run with the bat continued as he managed 15 before playing a loose shot off a short and wide delivery from Junaid only to find the other Akmal brother, Umar, at point.
Virat Kohli carried on his unimpressive run in the series and edged Junaid to Younis Khan at second slip. Kohli, who has been India's highest run getter in both Tests and ODIs this season, managed seven and has failed to get to double figures in this series. The Delhi boy failed to open his account in Chennai and got just six in Kolkata.
Junaid and Irfan left India struggling at 37/3. Junaid's first spell read 7-1-12-1 and Irfan's 7-1-28-2.
Runs were hard to come by when the two fast bowlers were in action during the first 14 overs. India merely scored 43/3.
Yuvraj Singh (23) started off well with two consecutive boundaries off Irfan. The southpaw also came down hard on Umar Gul.
Yuvraj hit Gul for three boundaries as the pacer gave 18 runs from his first over after coming in as a first change for Irfan.
But Yuvraj's flashy innings ended after he was castled by Mohammed Hafeez (1/44).
Dhoni and Raina tried to repair the innings with their 48-run stand but Ajmal wrecked the middle-order.
Ajmal picked up Raina and Ravichandran Ashwin (0) in consecutive deliveries while Dhoni fell to Gul, caught at point by Umar.
The last four wickets all went to Ajmal as India slumped from 131/6 to 167 all out. Ravindra Jadeja (27) hit some lusty blows, but it was not enough to save India from the ignominy of not being able to play the full 50 overs.