miss fire

Hi Everyone ... Can a weak battery throw misfire codes in a 2000 540i ?White smoke is seen too early in morning but sometimes only..one it didnt start n when i got a jump it smoked.. one mechanic say it can especially early in the morning ..Any advice on this ? another said coolant leak, another said valve seals, car did a full tune up all dealer parts in june .. this only happens once in a while

Waek battery maybe--my first bet would be Vacuum leaks--how the fuel mileage and engines power doing out on the road--if both are down--bet you have a vac leak somewhere

thanks..the power not too bad but, today i went under n checked the catalytic converters , the left rear driver side sounds bad inside when i tap it ...can that cause enough back pressure to cause that...it did throw a calalitic code too ,since i have all brand new bosch sensors too...it was at bmw dealer few month back for complete diagnostics and they found a vacume line cracked after doing a smoked test it was replaced tho...can it be a new one?

Clogged cats can cause misfires, but they are generally random multiple misfires on the bank with the clogged cat.

Ok Thanks allot I think that is exactly what's going on ....the computer did say random misfire and today no smoke and very little engine shake ..its crazy...i'm gonna change the cheapest cat in the failed bank first ...the one thats broken inside isbank 2 rear ( driver side) crossing my fingers it solves the problem and i don't need to change the front one

If it has power at all and drives OK out on the road--it isn't a cat that's the problem--a cat will let the car go only so fast and then feel like the car is surging--check out for vac leaks first--they can cause the very problem you experiencing

ok thanks ...will do

Originally Posted by poolman

check out for vac leaks first--

For misfires, look here ...
- How to diagnose a BMW E39 engine misfire (1)

Found a leak at the throttle body gasket ,,thanks guys .. will change it and let you know how she runs