M20 producing atrocious mpg. Update 15/6/16

[dimebag_from_hell]

Alright lads, got an m20 here running very smooth, no issues at all bar it's very sore on fuel.

Basically in less than 20 miles driving sheepishly, over a tenner of petrol used.

She smells rich but then again they all seem to.

When I changed the oil it stank of petrol.

There are no obvious leaks but I haven't specifically checked yet.

What's the protocol, where to start, what to eliminate?

Thanks

[andysheep]

Iv put my cabby m20b20 on a auto box on the road last week and jesus it drinks like a scotsman ,but like you said they all do that,good luck cos not even mine drinks that much
Andy

[Speedtouch]

Check out the Zone Wiki guide:

http://www.e30zone.net/e30zonewiki/inde ... n_Problems

[Brianmoooore]

Pi**ed as a newt, on the wrong end of a bottle of red, sitting by the Loire near Nevers, but I can still just about type! Check out the blue temp. sensor resistances, hot and cold, AT THE ECU PLUG, is the first thing to check, but you reallyneed a printout from an exhaust gas test. Always ask for this at a MOT test.

[aimlessrock]

are the HT leads original or aftermarket- does it have a CID?

http://www.e30zone.net/e30zonewiki/index.php/CID

[aimlessrock]

Pi**ed as a newt, on the wrong end of a bottle of red, sitting by the Loire near Nevers, but I can still just about type! Check out the blue temp. sensor resistances, hot and cold, AT THE ECU PLUG, is the first thing to check, but you reallyneed a printout from an exhaust gas test. Always ask for this at a MOT test.

lol- sounds good Brian.

[reggid]

id check FPR first and leaks

[dimebag_from_hell]

How would you test fuel pressure regulator? With the amount of fuel its using I can't imagine it's leaking, I have a tiled garage floor and just think I would see evidence of this somewhere.

The thing is it idles perfectly from cold, never stalls, in fact it's perfect bar the amount of fuel its using.

[reggid]

using a pressure gauge.... you can also pull the vacuum hose off the back see there is fuel in there sometimes they leak into vacuum hose indicating a fault. what MPG you getting now and a few months back?

[dimebag_from_hell]

She was always sore on fuel being a m20 but now I might aswell by driving a hummer.

[dimebag_from_hell]

Pi**ed as a newt, on the wrong end of a bottle of red, sitting by the Loire near Nevers, but I can still just about type! Check out the blue temp. sensor resistances, hot and cold, AT THE ECU PLUG, is the first thing to check, but you reallyneed a printout from an exhaust gas test. Always ask for this at a MOT test.

I'm finally getting free time to look at this later, do you have to remove the ECU from the glove box to get to the ECU plug?

[dimebag_from_hell]

Ok plug located, it's a 35 pin plug


Pin Function Pin Function Image
1 Ignition coil output 19 Ground Image:Motronic1_0Pins.jpg
2 Idle switch 20 Main relay
3 WOT switch 21 Tachometer
4 Cranking signal 22 AFM Temp sensor
5 Ground/Crank PosS Gnd 23 Inlet Air Temp/Crank SpS Gnd
6 AFM ground 24 O2 sensor signal *
7 AFM signal 25 Crank position sensor 1
8 Crank speed sensor 1 26 Crank position sensor 2
9 AFM supply 27 Crank speed sensor 2
10 Auto only special 28 Water Pressure switch
11 Fuel consumption gauge 29 A/C switch (if installed)
12 30 +Inlet Air Temp
13 Water Temp 31
14 Injector output cyl 3&4 32
15 Injector output cyl 1&2 33 ICV pulse
16 Ground 34 ICV pulse
17 Ground 35 Injector ground
18


The e30 wiki guide states, "Putt your multimeter electrodes onto pins 24 and 45 of the ECU (for facelift engines. For others, such as the 318iS, check the ECU Pinouts)"

Pin 24 is ground and 45 is coolant temp input, the pinouts for the 35 pin plug do not show a pin for coolant temperature input, can anyone advise further?

http://www.e30zone.net/e30zonewiki/inde ... CU_Pinouts


EDIT

So this is what I have



Going by the e30 wiki link, pin 13 is coolant temp but looking at the plug there isn't a pin at position 13....

[dimebag_from_hell]

Anyone? Cars up for MOT on Monday so desperate to get this sorted.

Just test at the sensor itself? Was going to just take it of, test it from cold and then dip the sensor in a cup of hot water and test it.

[jmc330i]

Pi**ed as a newt, on the wrong end of a bottle of red, sitting by the Loire near Nevers, but I can still just about type! Check out the blue temp. sensor resistances, hot and cold, AT THE ECU PLUG, is the first thing to check, but you reallyneed a printout from an exhaust gas test. Always ask for this at a MOT test.

I'm finally getting free time to look at this later, do you have to remove the ECU from the glove box to get to the ECU plug?

ECU is drivers side on a RHD car, not above the glovebox.

[jmc330i]

Anyone? Cars up for MOT on Monday so desperate to get this sorted.

Just test at the sensor itself? Was going to just take it of, test it from cold and then dip the sensor in a cup of hot water and test it.

You need to check the sensor from the ECU end to rule out any wiring issues and make sure the ECU is receiving the signal from the sensor. There is a plug under the inlet manifold that can cause issues, so it's important to check at the ECU end.

[dimebag_from_hell]

Pi**ed as a newt, on the wrong end of a bottle of red, sitting by the Loire near Nevers, but I can still just about type! Check out the blue temp. sensor resistances, hot and cold, AT THE ECU PLUG, is the first thing to check, but you reallyneed a printout from an exhaust gas test. Always ask for this at a MOT test.

I'm finally getting free time to look at this later, do you have to remove the ECU from the glove box to get to the ECU plug?

ECU is drivers side on a RHD car, not above the glovebox.

Jesus Christ epic fail!

Will have a look when I'm home. Thanks!

[dimebag_from_hell]

So from cold I get 2800 ohms and hot 250, sounds about right. Obviously never bothered testing at the blue temp itself after getting those readings.

From experience where would you chaps reccomend checking next. Fuel tank looks good, no visible signs of leaks on garage floor.

[dimebag_from_hell]

So I am reading the C191 plug could be at fault, is there any issues when removing the intake manifold? I am at work trying to visualise it in my head.

I must stress this car started perfectly after a few years of no use, it idles perfectly, drives perfectly with no misfires....so I am hoping that will narrow down what could be the issue.

Could a leaking injector be the cause? The oil that came out of it stank of petrol.

Did the "wild chip" which I believe was supplied on here by ant, known to cause excessive fueling?

I am mad to get this sorted as I have a 300 mile journey to do in it to a car show on the 18th

[Brianmoooore]

You've already tested the C191 if you've checked the temp. sensor at the ECU.
Have you taken all the spark plugs out and checked them all for the colour of their tips?

[dimebag_from_hell]

Yes Brian, I removed them when doing the timing belt. They were bmw Bosch and like new.

Any other ideas?

Thanks!

[pianist]

Brand new is not a colour, we need to know if the tips are brown, black, white etc

[Brianmoooore]

^ ^ ^ ^

What he said!

Condition isn't what we need to know. Colour is.

[dimebag_from_hell]

^ ^ ^ ^

What he said!

Condition isn't what we need to know. Colour is.

Standard greyish colour

[Brianmoooore]

Second pic. is too out of focus to see anything, but the first pic., although from the wrong angle, appears to be a little on the black (rich) side.

[dimebag_from_hell]

I'm getting pretty much single figure mpg, blue temps good, C191 good, what'I would you suggest to check next Brian? Thanks

[jmc330i]

I'm getting pretty much single figure mpg

How are you calculating the mpg?

[dimebag_from_hell]

I'm getting pretty much single figure mpg

How are you calculating the mpg?

As I know I've used at least 10 litres of petrol in within 20 miles.

[reggid]

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

[Brianmoooore]

As I know I've used at least 10 litres of petrol in within 20 miles.

That must be a leak! If the engine was burning it at that rate (less than 10MPG), then the plug tips would be a ball of soot.
A leak in the form of a fine spray from a high pressure fuel hose, that only occurs when the engine is running, can be surprisingly difficult to detect.
I remember one years ago when I only found it when the back of my hand happened to pass through the jet.

[dimebag_from_hell]

The fuel hoses are beneath the air intake? If a leak cannot be detected by hand would it be worth just replacing them all?

[Brianmoooore]

There are hoses at the rear of the car as well. They usually fare better than those in the engine bay, since they're not exposed to so much heat, but they can still fail.
Bending a hose will show if it needs replacing - cracks into the braid are not good.
Did this drop in MPG happen suddenly?

[dimebag_from_hell]

No Brian, I always felt it ran rich but after a long lay up, couple of years, it's using an excessive amount of fuel

[jmc330i]

I'm getting pretty much single figure mpg

How are you calculating the mpg?

As I know I've used at least 10 litres of petrol in within 20 miles.

How do you know?

[dimebag_from_hell]

I know what your trying to get at, however I know the car, have owned it for years and can tell from the guage that I've used at least a tenner of fuel.

[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?

I'm going to check the fuel hoses tomorrow after work. Is there much to remove to get to them?

Thanks