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hello, i have a volvo s40 1996 2.0 with engine code B4204S,
i have some trouble with that it as poor acceleration, slow gas response,
uses alot of fuel and it's "jerking" while driving at continious RPM,
it also getting worse when it's high air humidity,
i was thinking maf sensor, but not finding it.
sometimes the acceleration is better, but this is only temporary. do anyone have any idea what it could be?

so far i have changed plugs, all vacum hoses ( i think), filters, cleaned all electric connections.
i was by mistake braking off one of the nipples on the evap system, but the problems was there before that, so now i removed it and put a screw with some silicone in the hose for the system.
the evap sensor here is extremely expensive here, so hope i don't have to change that.

i tried to run diagnose, but none of my tools or software can't connect to ecu.

any ideas besides the evap?
 

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Is it ever hard to start? especially when hot? With the mpg going down and the rougher running i'd suspect the fuel pressure regulator may be leaking. This would cause uneven fuel trims and also leak down residual pressure in the rail, making it respond poorly and run roughly. Do you have any engine codes or lights on dash?
 

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Could also be the crankcase vent system is plugged and causing positive pressure on the crankcase.
 
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