325 coupe rough

[hazzard]

Hi dont know if anyone can help, i have a 325i coupe on a 1992, and has just started to missfire at tickover and hesatates under 2500 revs... aslo it has gone vary heavy on fuel, whilst the mpg needle in waving up and down at a steady speed .....

any ideas would be great.....
thanks:cry:

[Crcrzy12]

check your 02 sensors or fuel injectors (fuel system in general).

[fun2drive]

You have either bad coils or bad coil boots.
All your symptoms point to that as well as the year car you have is noted for bad coils.
Do a search and you will see what I mean.
Poor fuel economy can be many things such as an O2 sensor.
Are you thowing any codes (CEL)?
By the way your car should have only one O2 sensor before the cat...

[cbouchez]

start with the spark plugs and then O2 sensor.

[DFrolka]

Having the same prob, 92 325is. One bad zundspule coil made me replace all 6, new plugs, found a cracked intake tube (mass air to throttle), the fuel regulator hoses always fall off - hose clamp it, o2 sensors need replacement every 50k and the real bugger - IT STILL MISSES! I'm in cali and it wont pass smog with the miss. I did read somewhere that the 92 M50 2.5L was only a one year release engine and is equipped with a hotter cam than the rest of the years, and to expect a rough lumpy idle.

[DFrolka]

Oh yea, the valve covers usually leak right around the spark plug hole and fill that cavity with oil or water if you wash it. This shorts out the coil. Between this and the fact that the zundspule's crack, both lead to severe ecu damage - ecu replacement is not cheap.

[lesl2]

If you suspect the ignition system, meter the resistance on the coils and boots. Compare the results. Inspect/clean/replace the plugs.

Because your mileage meter is fluctuating, it sounds more like a vacuum leak. Check all your hoses for a vacuum leak. Pinch them and listen for changes in idle speed. Spray carb cleaner around the injectors to check for leaks. Be sure the oil cap and dip stick are secure.