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Car Forum / BMW Cars / January 2009Strange fuel consumption on a 330t
My brother recently bought an 00 330t manual. Seems to run just fine. Fuel consumption on his sort of local journeys is ok - about 24 mpg UK. On most long journeys he tows a caravan - so lets ignore that bit. ;-) But recently he did 500 miles plus without caravan. Consumption according to the OBC was 27 mpg - and he stuck to the speed limit. Doing the exact same journey in my 528 auto gives 32 every time. My first thought was a dirty air filter - but that's been changed recently. Any guesses?  Signature*It's this dirty because I washed it with your wife's knickers* Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > My brother recently bought an 00 330t manual. Seems to run just fine. Fuel > consumption on his sort of local journeys is ok - about 24 mpg UK. On most [quoted text clipped - 6 lines] > My first thought was a dirty air filter - but that's been changed > recently. Any guesses? The usual suspects are tire pressure, spark plugs and O2 sensors. I'd also check for a plugged catalytic converter. FloydR > > My first thought was a dirty air filter - but that's been changed > > recently. Any guesses? > The usual suspects are tire pressure, spark plugs and O2 sensors. Definitely not the first - as he has to alter them regularly for towing. I'd have thought the spark plugs would cause missing if making that much difference? O2 sensor problem would presumably show up on a diagnostic check? > I'd also check for a plugged catalytic converter. But would a blocked cat? Signature*I finally got my head together, now my body is falling apart. Dave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. > Floyd Rogers <fbloogyuds@hotmail.com> wrote: >> > My first thought was a dirty air filter - but that's been changed [quoted text clipped - 5 lines] > I'd have thought the spark plugs would cause missing if making that much > difference? No, a mis-fire would trigger the engine check - at least in the US with OBDII; not sure in EU. I got about 1mpg more after changing plugs at 120K (after 60K) miles. > O2 sensor problem would presumably show up on a diagnostic check? In the US, a failing O2 would usually trigger the check engine. But it's possible that all 4 (in the US) getting "weak" might not trigger it but significantly affect performance. >> I'd also check for a plugged catalytic converter. > > But would a blocked cat? A cat can fail slowly over time, or just fall apart suddenly. It just depends. FloydR >In the US, a failing O2 would usually trigger the check engine. But it's >possible that all 4 (in the US) 4?? >getting "weak" might not trigger it but >significantly affect performance. I doubt that. > Floyd Rogers wrote: > >>In the US, a failing O2 would usually trigger the check engine. But it's >>possible that all 4 (in the US) > > 4?? 4. http://www.realoem.com/bmw/showparts.do?model=ES53&mospid=47726&btnr=11_2181&hg= 11&fg=50 >> Floyd Rogers wrote: >> [quoted text clipped - 6 lines] > >http://www.realoem.com/bmw/showparts.do?model=ES53&mospid=47726&btnr=11_2181&hg= 11&fg=50 What's the difference between a REGULATING LAMBDA PROBE and a LAMBDA MONITOR SENSOR? > Floyd Rogers wrote: >>> Floyd Rogers wrote: [quoted text clipped - 11 lines] > What's the difference between a REGULATING LAMBDA PROBE and a LAMBDA > MONITOR SENSOR? One provides a reference from before the converter, the other tells the control system that just enough O2 was in the exhaust to burn the hydrocarbons, NOx and CO in the converter. This allows the leanest burn (complete combustion, best mileage.) Just knowing there is no O2 downstream isn't sufficient to ensure lean burn, or that all the pollutants got burned. Google "closed-loop control". Floyd Does it run cool? A lot of these seem to have sticking thermostats causing the engine never to reach the correct temperature. It should be in the middle of the gauge. SignatureWho needs a life when you've got Unix? :-) Email: john@unixnerd.demon.co.uk, John G.Burns B.Eng, Bonny Scotland Web : http://www.unixnerd.demon.co.uk - The Ultimate BMW Homepage! Need Sun or HP Unix kit? http://www.unixnerd.demon.co.uk/unix.html www.Strathspey.co.uk - Quality Binoculars at a Sensible price > My first thought was a dirty air filter - but that's been changed > recently. Any guesses? usually losing the oxygen sensor results in higher gas consumption as the computer trys to run the engine without proper information coming in as it is burned out (precious metals that make the chemical reduction into an electical impulse have worn away from heat, petrol, and the cleaners that one used from time to time putting in a leptokertic wear curve on the engine parts ... for faster wear. Steady on with the correct petrol mix works best on these beamers. oxygen sensor is usually easy to access and swap out at the bottom of the exhaust pipe outside of the engine manifold ... however it must be tested to know if that is what the problem is. also ... if you have dash lights that stay on after engine start for a long time before winking out ... then you have wearing parts. for the 500 series ... a turn key brings on 5 green bars, starting dashlights go out straight away ... car passes smog right then and there if all the parts are sorted out correctly. later on ... 4 green bars show up .. then 3 green bars better be in the shop right quick. 2 green bars or less, dash lights on, tow it in. sumbuddie hopes that helps :) >oxygen sensor is usually easy to access and swap out at the bottom of the >exhaust pipe outside of the engine manifold ... however it must be tested to >know if that is what the problem is. My understanding is that there are two, and at least one of them is quite difficult to replace, hence the over-US$1k expense, if done at the stealership. > oxygen sensor ... must be tested. Your O2 sensor might be just fine as well as all your electrical fittings. What looks and sounds like the same problem as you are describing, is a filled up EGR value or sorts in the smog system ... for example. Way back in the day, there were no rubber tubes and pipes around and smog pumps and such. There was just a 6 cylinder block all sealed up for example ... you can see them on those old black and white newsreals of American Troops at the Battle of the Bulge in Bastogne ... they are huddled around a jeep ... and there is this ball cloud of smoke, haze around them. That is the burning petrol products .. it could be all bio-diesel fuel lubricants ... and it will still smoke, and carbon up and cook like any greasy spoon kitchen on fire all day with greeze balls slinging about. With bio-fuel .. there is an 80% reduction in green house gas over petroleum regardless of the engine situation. It smokes, it makes smog, tis a haze burning up .. and they came up with a Positive Crankcase Ventilation ... PCV value .. that suck by negative pressure from the the bottom of the carburator ... down a rubber pipe ... stuck into the valve cover after they drilled in a hole from the existing engine. It was an adaptation ... ordered by the Department of Defense ... have to keep our troops alive you know .. not kill them off ... they are valuable .. this first smog control device if you will. After that .. they were like the devil possessed with oil ... they came up with gazzziol values and miles of tubes .. and they all fill up with carbon. Even coming up with a carbon sack that fails after 20 years and destroys the engine by dumping a few pounds of carbon dust into your engine .. if you have that sitation. Anyhow ..once the value is identified like the EGR value example after maybe 50k miles .. they swap it out ... and the engine ventilates properly ... all is well. Sooooo ... just swapping out the oxygen sensor stuff ... might not be of any help to you at all and a waste of money. Better then 50/50 it will not be it, the problem will be something else. Unless you go to a BMW certified mechanic and have them get the dash lights to go off right after start up ... maybe get successfull after they test it out and dx it properly and getting it right straight away. The longer you let the engine work harshly .. the faster it breaks down from improper use. Oil leaks will make a 'cool' spot on the engine, and warp the block over time, running just fine ... until you have to crack the case for deep maintance ... it will not fix back properly ... constant head gasket blowing up for example as replacement made to fit parts are going back into a warped engine and just will not fit anymore. Toast the engine .. toss the car ... engine is worth more. sumbuddie hopes that helps :) > My brother recently bought an 00 330t manual. Seems to run just fine. Fuel > consumption on his sort of local journeys is ok - about 24 mpg UK. On most [quoted text clipped - 6 lines] > My first thought was a dirty air filter - but that's been changed > recently. Any guesses? Has the OBC accuracy (for both vehicles) been checked against actual distance covered divided by fuel consumed (preferably over 3 or 4 tanks)? The one on my E46 is about 9% optimistic but the one on my 128i is actually about 1% pessimistic. My '99 328i 5-speed is pretty consistent at around 30 U.S. mpg for 70 mph highway cruising, which should be comparable to your auto 528i. Tom > My brother recently bought an 00 330t manual. Seems to run just fine. Fuel > consumption on his sort of local journeys is ok - about 24 mpg UK. On most [quoted text clipped - 6 lines] > My first thought was a dirty air filter - but that's been changed > recently. Any guesses? Reset the OBC? > My brother recently bought an 00 330t manual. Seems to run just fine. Fuel > consumption on his sort of local journeys is ok - about 24 mpg UK. On most [quoted text clipped - 6 lines] > My first thought was a dirty air filter - but that's been changed > recently. Any guesses? Do both cars turn the same rpm at the same road speed? If not, the one with the higher engine speed will (usually) have poorer mileage. lj > > My brother recently bought an 00 330t manual. Seems to run just fine. > > Fuel consumption on his sort of local journeys is ok - about 24 mpg [quoted text clipped - 7 lines] > > My first thought was a dirty air filter - but that's been changed > > recently. Any guesses? > Do both cars turn the same rpm at the same road speed? If not, the one > with the higher engine speed will (usually) have poorer mileage. My 528 is higher geared - but my thoughts are that wouldn't account for such a large difference. Especially given the 330 is newer and lighter. SignatureDave Plowman dave@davenoise.co.uk London SW To e-mail, change noise into sound. |
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