Intermittant code P0300 on '98 V70 R

Post by **scoobycant** » 22 May 2009, 07:14

Getting code P0300 - misfire detected multiple cylinders. Car starts, idles, and drives well. I've cleared the code 5 times within the last month. Comes back, sometimes after 20 miles, sometimes after 500 miles. When code sets, it has always been under light load at slow (< 20 mph). Freeze frame data lists Fuel Sys 2 CL-fault, engine load 1.9%. I have replaced fuel filter, plugs, wires, cap, rotor within past 20,000 mi. Been driving with Techron fuel system cleaner for about 1000 miles since code first set. Started getting this code after I replaced the radiator and radiator hoses a month ago. Could this code be caused by a small vacuum leak? Can a vacuum leak be small enough to not affect idle quality but problematic at light load? Thanks in advance for any information.

Post by **MadeInJapan** » 22 May 2009, 17:39

Just for kicks, how's your temperature gauge on your instrument cluster?

Post by **scoobycant** » 22 May 2009, 18:45

I put in a new coolant temperature sensor during the thermostat/housing project you helped me with a couple of weeks ago. Thanks again. Temperature gauge is at mid-range, 3 o'clock position. No history of overheating. Talked this afternoon with a service manager at my local Volvo dealer. He doubts that a vacuum leak could cause multiple misfires without setting other codes, too. I've done a "visual" on the hoses that I disconnected for the radiator R&R. Tomorrow, weather permitting, I'm going to re-check with propane. By the way, I replaced the ignition coil when I did the plugs, wires, cap, and rotor.

Post by **scoobycant** » 24 May 2009, 13:40

Ok, didn't find anything with the propane. But I did find a loose clamp at the joint between the MAF sensor and the air inlet duct to the turbo. I had loosened this to gain access while replacing the lower radiator hose. Got a full 3 turns on the clamp. I'm hoping this was the source of my intermittent code.