E36 320 drop off in fuel economy

[McAndy]

Hi All

I had my 1995 320i serviced in December, new tyres etc, tracking checked post pothole clunk, but I've noticed a drop off in miles per tank of around 80 miles. It has 3 green service lights left and I've checked the oil (possibly a little over full if anything). It ought to be in very good mechanical health...does anybody have any ideas what could be causing it? Should I check the oil filter even though it's been serviced recently? It's still picking up fine and feels like it's warming through quickly in the mornings.

Sorry for not having many symptoms to go on...I am only an amateur when it comes to vehicular surgery (although learning fast!).

Many thanks

Andy

[TheEnd]

at a rough guess, your lambda sensor has died, but tricky to confirm without diagnostic stuff

[McAndy]

TheEnd said:

at a rough guess, your lambda sensor has died, but tricky to confirm without diagnostic stuff

Cheers TE. What other symptoms may this cause please?

[TheEnd]

the main one is a drop in economy, and the idle might be a little more lumpy.
sometimes you will get a petrol smell from the exhaust, but that's pretty common in cold weather, so not always a good sign

[Shropshiremike]

Also McAndy, since when has your fuel economy dropped off? If it's since about December or last few months it may be attributable to the recent cold weather ( depending on where you live? ). Some people leave their car ticking over while they scrape ice/snow off their windscreen on cold mornings and doing this for a few mins will bring down your average consumption. A difference of of 4 or 5 mpg over a tankful can make a difference close to what you are getting.
On my E36 I average a few more mpg in the summer/warmer months than I do in the winter ( even allowing for the fact I drive a bit quicker on warm/dry roads than snowy/icy corners ).

I'd echo what Enda said as well. I changed the lambdas on my 328 as they'd got sluggish in operation. The hardest part was routing the cabling in between the back of the block and the bulkhead. There were spring clips on mine for tghe wiring and you need hands like a girl/kid to get in there without scuffed knuckles. The mpg did perk up slightly. I think you only have one on yours rather than twins on the 328?

Make sure they've changed the air filter as well ( even though you say it has been serviced, some places can overlook this )

[McAndy]

Thanks TE, Mike. That gives me some thing to hunt around for and see if there are trends. Greatly appreciated!