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Enes, VOLVO Master Technician
Category: Volvo
Satisfied Customers: 5477
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I have a 2001 Volvo S40 that has the following OBD codes:

Customer Question

I have a 2001 Volvo S40 that has the following OBD codes: P0301, P0302, P0303, P0304, P0133 and P0171. I changed the spark plugs and it was running fine right afterwards but the next time I started it up it stalled, seemed to be missing, would stall at idle and intermittently would run fine on high throttle I've rented a fuel pressure regulator to check the fuel rail but don't know what that pressure should be. I will also check the vacuum on the pressure regulator to see if it is cracked or has fuel in the line after reading a previous answer. Any other thoughts? thanks
Submitted: 1 year ago.
Category: Volvo
Expert:  Enes replied 1 year ago.

you can check that fuel pressure regulator first unplug vacuum hose look for fuel smell than remove spark plugs and inspect them again ? also you can have 2 bad coils the*****all 4 cylinder and you have misfire per codes on all 4 check that also pay close attention to wiring small wires can get pinched and short to block and crate misfire very easy missed and very common wire damage under the spark plug cover look very close

Customer: replied 1 year ago.
All plugs had spark, didn't measure any pressure at the fuel rail No fuel in regulator vacuum line. How do I check if regulator or fuel pump is bad?
Customer: replied 1 year ago.
No response, is my question still open? Thanks
Expert:  Enes replied 1 year ago.