14mpg!!!

hello all, this is my first post since i picked up my '92 325i manual. i hit cheshire last friday and blasted all the way home. huge thanks to steven.seed who was a huge source of help and info. (he went as far as picking me up from the airport and bringing me to the dealer).

will take a few pics soon. now, the fun stuff.

i've read back a lot through the various threads about my problem and i'm fairly sure it's either the air-flow meter or lambda sensor but i'm open to correction.

the symptoms are -1) 20 mpg over the 300 mile trip home. and 14mpg on the subsequent tank of petrol (180 miles or so). needle usually reads about 20mpg at 55mph in 5th.

                            2) occasional chugging/ spluttering at around 40mph.

                             3) smokiness and hunting

                             4) every so often, at around 55mph, the mpg needle will jump to around 40mpg. if i pull in, the engine doesn't hunt even after a few minutes and when i pull away, it runs very smoothly.

any thoughts??

didn't get a chance to get the car checked out yet. it seems every decent mechanic in the country has a 2 week waiting list which isn't very handy if you're wondering if you're doing your car car harm by driving it every day.

as a small sub-point, the car has started trying to die every so often. it kind of chugs and loses power for a few minutes, whenever i press the accelerator. if itake my foot off the accelerator, it decellerates as it should, but press it again and she starts chugging. pull in to the side of the road and give it a minute and it'll pull like a train again.

thanks for your help andy. i have learned on many occasions the hard way (read: expensive way) that i am officially.....all thumbs!

on one particular occasion, i ended up ordering new headlamp for one of my last cars. the guy in the motorfactors told me "oh, you can actually get the lens on it's own" to which i replied that the lens was fine, everything else in there is knackered including the beam adjuster motor. that was the last time i ever tried to change a parking lamp