Started racing in 1976. Won the Spanish Touring Car Championship in 1981. In 1986 he moved to sportscars with the Brun Porsche 962, winning at Jerez with Oscar Larrauri. They finished 2nd in Le Mans 24 Hrs that year.
On September 23, 1990 while participating in a World Sports Championship race in Montreal, Quebec, Canada, Team Bruns driver Pareja had a close encounter with a manhole cover. Driving fairly close behind a Jaguar in his Porsche 962C, Pareja soon discovered the effects of the suction effect race cars have on the track. The updraft of the Jaguar in front of him dislodged a manhole cover and sent in flying through the air. At least until it made contact with Pareja's racecar. At this point the manhole cover smashed through the Porsche's windshield, narrowly missing Pareja and piercing through the rear of the car, tearing the fuel tank apart. Both this and the impact with the wall the Porsche experienced caused the $750,000 car to burst into flames. Luckily Pareja came out alive, and probably not too fond of manhole covers any more. The manhole covers are since welded down for raceday at that track.
In 1997 he drove the BRM P301- LMP1 at Le Mans with Harri Toivonen and Eliseo Salazar. The car was a development of the 1992 P351 Group C car but with a Nissan twin turbo V6 engine from Clayton Cunningham of the USA. Entered by Pacific Racing, the car retired after just six laps with engine problems.
Retired from racing in 1997 to set up the GT Sport company. 2000 his company ran the Spanish GT Championship and in 2001 ran the Spanish F3 Championship.