M20 producing atrocious mpg. Update 15/6/16

[reggid]

ok lets get serious and a proper test. fill up the tank full with fuel (makes sure its full) reset the odo button thingy or note the odo and drive until the fuel light comes on and fill it up at the same pump. how many miles do you do and how many litres/gallons do you use?

you might just be a crap driver with lead in your shoes? but 30L/100km is impressive

[dimebag_from_hell]

Irrespective of mpg, I'm know I'm either over fueling or have a leak, I don't need to run a full tank of fuel through to confirm this.

[Cloggy Saint]

If you had this kind of leak I'm pretty sure you'd smell it. I had a small split in a fuel line that didn't affect mpg and it reeked.

[dimebag_from_hell]

You can smell it when it's running but cannot tell if it's coming from the exhaust or fuel hoses. Going to inspect the hoses tomorrow and eliminate that issue.

What I will say is, the oil that came out of it stank of petrol. which injector is typically the culprit for leaking?

[jmc330i]

those plugs dont look like bill gates rich. how long had the car been idling before pulling them? plugs might suggest it might be under load that is overlfuelling rather than at all times and at idle its ok? if so could be AFM

It idled for about 10 minutes a day or two before I tested the blue temp sensor.

Surely if the AFM was faulty the car wouldn't be driving so good?

Surely the car wouldn't be running so good if it's actually trying to burn enough fuel for 9mpg???

[BenHar]

ok lets get serious and a proper test. fill up the tank full with fuel (makes sure its full) reset the odo button thingy or note the odo and drive until the fuel light comes on and fill it up at the same pump. how many miles do you do and how many litres/gallons do you use?

You don't have to run it to the fuel light. Just fill it up, drive it for 30 miles or so and then refill it.

Ben

[Brianmoooore]

The worst ever MPG I achieved for an E30 (325 touring) was 19 MPG. This was towing a heavy, tall, flat fronted trailer, with the aero. of a barn door, as fast as I possibly could, for 200 miles, along a major A road, into a strong head wind.

[dimebag_from_hell]

those plugs dont look like bill gates rich. how long had the car been idling before pulling them? plugs might suggest it might be under load that is overlfuelling rather than at all times and at idle its ok? if so could be AFM

It idled for about 10 minutes a day or two before I tested the blue temp sensor.

Surely if the AFM was faulty the car wouldn't be driving so good?

Surely the car wouldn't be running so good if it's actually trying to burn enough fuel for 9mpg???

Yeah, so it must be leaking but I haven't seen anything obvious.

The worst ever MPG I achieved for an E30 (325 touring) was 19 MPG. This was towing a heavy, tall, flat fronted trailer, with the aero. of a barn door, as fast as I possibly could, for 200 miles, along a major A road, into a strong head wind.

lol!

Brian, is much needing removed to get to the fuel hoses?

cheers

[Brianmoooore]

Underbonnet fuel hoses are readily accessible on a M20, but there are also short ones around the fuel filter in front of the left rear wheel, the return pipe to the side of the tank, and the hose from the fuel pump.

[dimebag_from_hell]

thanks brian

[dimebag_from_hell]

Hoses checked, nothing obviously split.

Popped the dipstick, and despite having the oil changed less than 50 miles ago I can smell petrol of it.

[reggid]

did you pressurize the hoses (those that are under pressure) when inspecting?

check if the injectors are not leaking partially stuck open this can contaminate oil

[dimebag_from_hell]

Yeah I started the car, then inspected the hoses. They are like new, everything on the car is like new actually.

Going to pull the injectors today, would a leaky injector show on the print out from emissions on mot test. Increased hydrocarbons?

[Samcez]

Please update it here regurarly. I cannot pass MOT, high MPGs, car smells like running rich. Already replaced the Lambda sond, checked numerous things, the car was at 3 workshops. So far, no results. The problem is almost, if not the same, as yours. Thanks!

[Speedtouch]

Perhaps try running some Redex or similar injector cleaner through it for a week or so.

[dimebag_from_hell]

Please update it here regurarly. I cannot pass MOT, high MPGs, car smells like running rich. Already replaced the Lambda sond, checked numerous things, the car was at 3 workshops. So far, no results. The problem is almost, if not the same, as yours. Thanks!

MOT is tomorrow, so will let you know.

The print out for the emissions will be interesting.

[dimebag_from_hell]

So emission results are

CO at idle - 2.340%

HC - 128 ppm

Would a leaky injector affect a HC test?

[Speedtouch]

Almost certainly. The injectors should either squirt the requisite amount of fuel in a funnel spray pattern when requested to by the ECU, or not at all.

[dimebag_from_hell]

So going by that HC reading can we say the injectors are working as they should be?
What do you think of the carbon monoxide results, the limit is 3.5%....

[Speedtouch]

Sounds from your other thread that the readings are well within the limits. Perhaps add a dose of Redex or similar injector cleaner before embarking on your 300-mile trip - they should be pretty well cleaned by then...

[dimebag_from_hell]

I read that the CO emission result may be considered higher than normal? What have other zoners achieved for CO at MOT?

Will try redex.

[BenHar]

CO should be around 1%.

Ben

[dimebag_from_hell]

So what does everyone reckon, she's not getting enough air?

[dimebag_from_hell]

So bit of an update.

Checked FPR- seems fine.

Removed injectors which are getting flow rested and rebuilt tomorrow if necessary.

While injectors were out I removed the idle control valve and gave it a spray with carb clean, hoses seem ok but I was a bit alarmed at how easy the u bend metal connection to the throttle body came undone? Should I use some sort of sealant when attaching it again?

So I removed the throttle body, noticed the gasket has seen better days, going to call bmw tomorrow to see if they can do me next day delivery for a new one.



Is it safe to clean the throttle body with carb cleaner in terms of the ports where the coolant hose/ fuel hose attaches etc?

The rubber bung under the throttle body was also showing signs of degradation.




I read about how the tps attached to the bottom of the throttle body should click when throttle is fully opened? I don't hear that click BUT my car runs smooth, no stuttering, flats spots, anything. Anything to worry about?

The breather pipe from the cam cover to throttle body, is showing fine hair line cracks when I flexed the pipe, so hoping to get one next day delivery tomorrow.

I also found this plug which was not connected to anything and pulled back from the rest?

It was attached to the loom the tps is attached to iirc!

All advice appreciated.

[dimebag_from_hell]

So bit of an update.

Checked FPR- seems fine.

Removed injectors which are getting flow rested and rebuilt tomorrow if necessary.

While injectors were out I removed the idle control valve and gave it a spray with carb clean, hoses seem ok but I was a bit alarmed at how easy the u bend metal connection to the throttle body came undone?


Should I use some sort of sealant when attaching it again?

So I removed the throttle body, noticed the gasket has seen better days, going to call bmw tomorrow to see if they can do me next day delivery for a new one.



Is it safe to clean the throttle body with carb cleaner in terms of the ports where the coolant hose/ fuel hose attaches etc?

The rubber bung under the throttle body was also showing signs of degradation.




I read about how the tps attached to the bottom of the throttle body should click when throttle is fully opened? I don't hear that click BUT my car runs smooth, no stuttering, flats spots, anything. Anything to worry about?

The breather pipe from the cam cover to throttle body, is showing fine hair line cracks when I flexed the pipe, so hoping to get one next day delivery tomorrow.

I also found this plug which was not connected to anything and pulled back from the rest?



It was attached to the loom the tps is attached to iirc!

All advice appreciated.

[reggid]

Did you check fuel pressure as in numbers in psi or bar ? At idle and reving, with and without vacuum hose connected?
If the injectors are dirty a new filter is an idea.

TPS should work properly there are 3 settings so the Ecu know what map and fuelling. Check at the sensor then at ECU. Follow Bentley

You can silicone the metal hose connector but don't hard glue it in to reduce Chance if vacuum leak

[reggid]

Also why is there a rubber hose on the bottom of TB capped off?? The charcoal canister should hook onto that

[Carmo13]

I have a little bit of knowledge that i have built up from being a member on here for a few years but i do recommend that you wait for some reinforcement from a senior member. (A little bit of knowledge can be dangerous!)
Im pretty sure that the TPS should click just as the the throttle body butterfly moves from the fully closed position rather than the fully open position.
Also im fairly sure that many cars came with the rubber bung from the factory and it is a know air leak problem area.

[jmc330i]

Also why is there a rubber hose on the bottom of TB capped off?? The charcoal canister should hook onto that

I don't expect there is a charcoal canister fitted, not many 325i had cats fitted over here.

[aimlessrock]

I would be looking to replace the rubber bung as a matter of course as yours is perishing.

Now that you have removed your TB it would be wise to undo the three screws (part 6) (see the below link), once removed part 4 will come off and you can scrape what's left of the gasket off (replace with 5). Fitting is the reverse.

BTW the rubber bung in no 7.

Carb cleaner is fine to use.


http://www.realoem.com/bmw/enUS/showpar ... Id=13_1331

[dimebag_from_hell]

Yes aimlessrock, I treated that area of the TB last night with lubricating oil as it was particularly corroded.

Two screws came out this morning and the one closest the coolant pipe broke like cheese. Bastard.



Anyone reccomend the best way to tackle this, the screw diameter is particularly fine.

[Speedtouch]

Use a thin drill to create a pilot hole in the centre, then use a suitably sized Easy-out (reverse threaded screw) to unscrew it. Beware of el-cheapo ones though, because they'll probably just snap off.

Use a bit of heat from a blowtorch before attempting to unscrew it, and penetrating fluid such as PlusGas left to soak for an hour or so, to give you the best chance of unscrewing it.

If you have a MIG welder, you could try and weld a nut on top of the snapped stud, then try undoing it.

[dimebag_from_hell]

Cheers speed touch and everyone who has contributed to this thread. A few people I need to reply to and will do once I'm home from work.

[reggid]

had the same thing happen to the screws on mine

[aimlessrock]

is she a B20 or B25?

I mention this as I have 3 spare TB's for a B20 in my stash- more than one man will ever need.