Really bad mpg m40 316i

[cypriot_boy_2k7]

Right I'm totally fed up with it now, have changed and diagnosed everything.
Car runs better but mpg is really bad, before I done any work to it I was getting 12.9 mpg now I have diagnosed and changed a few bits, I've got it up to 18 mpg.
Things I have changed:
Afm
Ecu
Throttle body with tps
Icv
Rubber boot Afm to tb
Injectors
Dizzy cap
Rotor arm
Coil
Leads
Spark plugs
Piping for vacuum side of things
Rocker cover gasket
Fpr
Fuel filter
Blue temp sensor

Serviced a 3000 miles ago
I'm dead stuck, help!

[Brianmoooore]

What colour are the spark plug tips?

[cypriot_boy_2k7]

Brown/ Black on a first start it smokes and smells of fuel

[cypriot_boy_2k7]

Anyone?

[redcar]

Hi mate, shame to see that it's still not running right. The fact that it's running rich would suggest something is fundementally wrong or not functioning at all.

Does it start up and idle perfectly from cold? -- This info. will really help as it can give clues as to what may not be functioning.

Seeing as you've replaced a lot (with known working parts (which is helpful)), i'd definitely suggest checking the engine loom.
It's easy for wires going to connectors to actually be dislodged from the connector.

The loom on my 318is had wires pulled out from both the TPS and ICV connectors. To save the tedious process of checking all the connectors and loom is functional at the ecu and plugs, it may be worth replacing the whole engine loom for a working one.
I'd give you the loom from my old m40 engine, but you may have already guessed, the TPS and ICV connector have been cut off/stolen from it

[sweep]

Its not got a small fuel leak from the pipe that runs at the back of the inlet manifold has it?

[redcar]

Its not got a small fuel leak from the pipe that runs at the back of the inlet manifold has it?

Would this not cause it to run lean, rather than rich.

[sweep]

It would cause the bad fuel consumption

[cypriot_boy_2k7]

Hey redcar, im gutted mate, especially after all that. Yes it's starts up and runs ok I suppose, it does have a point during idle that's like a like pulse and change in sound. Before I change all that stuff you sold me it took ages to start and would run shiz till it warmed but even then it was running like a lump.

[bmw9818]

youve changed alot! id say check the loom as well if somethings come loose or any pins are corroded then that could be causing issues, if not that then just make sure all the bits are in good nick

id say also check the rubber pipes hidden by the inlet manifold going to the injector rail, when it was cold mine used to leak out,

[redcar]

Hey redcar, im gutted mate, especially after all that. Yes it's starts up and runs ok I suppose, it does have a point during idle that's like a like pulse and change in sound. Before I change all that stuff you sold me it took ages to start and would run shiz till it warmed but even then it was running like a lump.

That's a shame.

Definitely worth checking the loom though. Wires going to tps may be loose or broken. Causing rich running. Also the case for wires going to the coolant temp sensor.

[cypriot_boy_2k7]

Hey redcar, im gutted mate, especially after all that. Yes it's starts up and runs ok I suppose, it does have a point during idle that's like a like pulse and change in sound. Before I change all that stuff you sold me it took ages to start and would run shiz till it warmed but even then it was running like a lump.

That's a shame.

Definitely worth checking the loom though. Wires going to tps may be loose or broken. Causing rich running. Also the case for wires going to the coolant temp sensor.

I done the blue temp check at the ecu so that's fine, how do you test the tps wiring?

[redcar]

Hey redcar, im gutted mate, especially after all that. Yes it's starts up and runs ok I suppose, it does have a point during idle that's like a like pulse and change in sound. Before I change all that stuff you sold me it took ages to start and would run shiz till it warmed but even then it was running like a lump.

That's a shame.

Definitely worth checking the loom though. Wires going to tps may be loose or broken. Causing rich running. Also the case for wires going to the coolant temp sensor.

I done the blue temp check at the ecu so that's fine, how do you test the tps wiring?

Try find a known working loom, saves a bit of time spent testing the loom etc.

[cypriot_boy_2k7]

I'd rather test than spend more money

[jonny323i]

have you got the pulse wire on the spark plugs my mates car had thatmissing and it made a big difference

[cypriot_boy_2k7]

have you got the pulse wire on the spark plugs my mates car had thatmissing and it made a big difference

Yes I acquired it from redcar, what lead does it go on? Also I don't think it make a big difference? I may be wrong

[jonny323i]

i dont think it matters which wire its on but i could find out next time im down my dads as my car is in his garage
I have a complete 316i lux tourer that was running perfect and i got mpg from before the head gasket popped. Dont suppose you want a complete car to use as a donor and then make a profit on the rest

[cypriot_boy_2k7]

If I had room, yes if you could find out that would be good. Why don't you break it or source another head

[jonny323i]

Because im now running my 325i tourer instead it may be getting fixed as i had an aa insurance that covered breakdowns upto £500

[redcar]

When i disconnected this pulse lead sensor wire, it didn't even make a difference. I don't really know what it does.

It's worth clipping of the rubber on the connectors on the loom, especially for the TPS and ICV, and making sure that all the wires are in place properly.

Also, are you sure that you don't have a fuel leak? However, your symptoms definitely sound like the car is running very rich. Is there any chance you could get a good quality video of you starting the car from cold.

[cypriot_boy_2k7]

No fuel leaks can be seen nor smelt, I will get a video on Saturday

[Beechy]

Hi, I dont know if you've sorted this yet but it sounds like a similair problem ive had with my M40. It wasnt running great at all when i got it so i started to replace all of the usual service items and it was still lumpy and used a lot of juice.

so i replaced the idle control valve which helped a little but didnt solve it and then i came across a little gem on a random google search;

"If one of the coolant temperature sensors isn't working the ECU presumes that no reading means the engine is still cold and continues to use more fuel to try and get it to temperature!"

It made sense so i looked into it. Theyre both tucked right up under the inlet manifold towards the rear of the block:
one brown (which is the sender for the temp gauge)
one blue (ecu coolant temperature sensor)

I changed both whilst i had good access and also checked the adjustment of the TPS whilst i was there (it needed adjustment).
I checked the resistance of the injectors and made sure i cleaned the inlet faces right up as a technician at BMW told me that back in the day they suffered from gasket leaks and needed cleaning up and replacing. (I did all 3 gaskets)

I now have good MPG, possibly as a result of a few of those changes but its worked. I hope this helps!