Volvo Repair: Volvo 1998 S70, fuel pump relay, cam sensor

Question
hi, thank you for your help.....

i am having trouble with my volvo 1998 S70 series.
It is surging while cruising for no apparent reason and only for a sec or two, it happens about 3 times over 30km after warm up.  Our Volvo mechanic can't get a reading on his computer as to a problem, there are no warning lights.  We have checked all basics such as:
*Spark plugs
*ignition leads
*CDI ignition unit?
*Replaced fuel filters
*Checked fuel pump
*Checked fuel relay
*Distributor cap is clean, looks good
*Rotor Button good
*Fuel pump relay
*Checked vaccum hoses

Any advice you can offer with this i would be very grateful
Thanking you
regards
Cathy

Answer
Cathy, sounds like an intermittent problem with the Air mass meter or cam sensor.  Did he change the Spark Plugs and wires or did he just check them.  I have seen some strange stuff over the years.  It can be something very simple.  This is one of those things that we would have to drive and do our own tests.  Roger