Roma, Coma thrive in Dakar's Argentine heat
Mini's driver Nani Roma of Spain and co-driver Michel Perin compete during the 2014 Dakar Rally Stage 4 between San Juan and Chilecito, Argentina, on January 8, 2014
Roma, behind the wheel of a Mini, had led after three stages and he reasserted his authority on the gruelling 912km run from Chilecito to San Miguel de Tucuman.
Roma clocked 4hr 27min 01sec on the 527km timed section of the stage with South Africa's Giniel De Villiers, in a Toyota, and America's Robby Gordon, driving a Hummer, in third place.
In the overall standings, he now has a lead of 26min 28sec on Qatar's 2011 champion, and Mini teammate, Nasser Al-Attiyah of Qatar.
Carlos Sainz, the 2010 champion who had led overnight, slumped to sixth overall, almost an hour behind fellow Mini driver Roma, after a nightmare day where the Spanish veteran endured a number of navigational errors.
The motorcycling section of the race was shortened as the heat was deemed to be close to danger levels for the riders.
Former champion Coma, on a KTM, was declared the stage winner in a time of 3hr 02min 08sec, with fellow Spaniard Jordi Viladoms in second spot and Kuba Przygonski of Poland taking third.
"It was another tough day. It was really hot out there. It's also difficult in terms of navigation as well because of the rain last week which makes it difficult to see anything," said Coma.
"To get to the end of the stage, I rode for 10 km lost in a river bed. In general, it's tough for everyone. For the race lead, you can lose lots of time at any moment. When you open the way, it's a bit like playing Russian roulette."
In the overall standings, Coma has a 41min 10sec lead on Honda's Joan Barreda, the previous leader.