2001 volvo s40 with 188,000 km.
the customer is complaining that the car starts off sluggish, then all of a sudden kicks in at like 2500 rpm and accelerates very fast. also sometimes it wont have any power at all.
when you first start the car and sometimes while running, and after you shut it off there is a clicking noise coming from the fuel pump. I have never heard this before. He had a new pump installed and few months ago from bosch. also he has had a tune-up done.
I have checked fuel pressure ( 35psi at idle) boost pressure under hard accel is 10-12 psi. I tried another boost controller that is good and no change. It had 2 engine codes P0455 and P0172. I found a broken vacuum servo on the brake booster and changed it.
I do not see any other vacuum leaks, the engine idles nice and smooth.
any ideas or suggestions would be much appreciated.