Hi Amin, I had a chance to review the work records on my 262C. The previous owner appeared to be experiencing a problem like yours. FIRST ATTEMPT to resolve 2001: Work was done @ a Certified Volvo dealership,i) throttle plate was adjusted; ii) replaced dist. cap, arm & cables; Car was also experiencing poor fuel economy, the 02 sensor was replaced, SECOND ATTEMPT:Independent garage used, they replaced fuel distributor, aux air pipe seal, reconnected the vacuum supply hoses(correctly); ignition advance & warm enrichment device adjusted; THIRD ATTEMPT: @ same independent garage, adjusted fuel pressure regulator, basic fuel pressure to lower specs; re & re brake vacuum pump, new kit installed; lasted for 4 years, appears to have fixed the problem FOURTH ATTEMPT: replaced all injectors & reset engine. It appears that the primary problem was with the injectors. Other work in 2001 may have also contributed to resolution. In 2005, just attended to fuel injectors & reseting engine. Summary, looks like they had to make 3 attempts before they got it right. In 2005 the solution was to replace the injectors & reset engine. That seems to have worked. I've had the car since September 2005. Always starts, quick & runs without difficulty. The vacuum pump can be noisy. This symptom is erratic. Engine continues to run, noise comes & goes. Mechanic replaced the vacuum pump valve kit, symptom (erratic noise, like a hammer hitting the engine block) reappeared within days. The mechanic recommended disconnecting the vacuum hose. This has not resolved the problem. Motor is strong, lots of pep, the noisy vacuum pump is intermittent. Acceleration seems to correct problem. Comment: The Bertone V/6 is a piece of work, not too many can work on it. Lot of guess work & luck involved in correcting problems. I did a lot of research. The Douvrin PRV V/6 engine was a highly sophisticated joint effort of Volvo, Peugeot & Renault. I recently sat in a 1981 DeLorean & perused the Shop Manual. The DeLorean has the same engine. The problems mentioned above were cited in the manual. It is a highly, maybe even over, engineered engine. When running, a joy to drive, but wants to be pampered. Summary: check the injectors, ignition system and adjust to specs. Good luck, let me know how you make out. I love to drive my 262C. Solid & fast. A little annoying when the vacuum pumps acts up, but doesn't seem to slow it down. Bill