Hey Scotty, my sister recently bought her first car, a manual bmw e39 523i from 1998 with 150k miles on it.
However, when we had bought it and driven it home, we realised that the longer the car is driven and the more it gets up to temp the more it misfires, I haven't driven it that much but I believe it misfires less above 4k rpm. It also doesn't misfire if you give it very low gas at the lower rpms, only when you try to accelerate faster than a big rig on an upwards hill.
We believe previous owner tried changing the maf sensor because we found one in the trunk, haven't read codes because I only have a cheap Bluetooth 16 pin scanner and the car has a 20 pin port.
We tried with stp injector cleaner but no success.
You got any clue what it can be?
Best regards from Sweden.
For us to really help you we need the exact codes. If you don’t have the appropriate scanner, take to an auto parts store to scan for you. Here in the US, we can easily do that; not sure over there how feasible it is.
Find a good independent mechanic to read your car’s codes first.
And pray it isn't the head gasket, starting to go.
