205 Mi16 Suspected Overfueling

[rocky 0]

Hi Guys,

 

I believe my 205 mi16 is overfueling. Why?

 

-i can smell fuel when i open the windows (particularly passenger side)

-exhaust has strong fume smells (no smoke though)

-I got 50 miles from 10 litres of fuel, and i kept revs below 4000 rpm the whole fuel cycle (does this seem right?)

 

The car seems to run fine and is smooth, but it does not seem so economical, and the smell is of concern. I cannot see any visible leaks of fuel, but where should i be checking for this?

 

I use 98ron superunleaded.

[Mikey S 29 1 Cars]

Hi Guys,

 

I believe my 205 mi16 is overfueling. Why?

 

-i can smell fuel when i open the windows (particularly passenger side)

-exhaust has strong fume smells (no smoke though)

-I got 50 miles from 10 litres of fuel, and i kept revs below 4000 rpm the whole fuel cycle (does this seem right?)

 

The car seems to run fine and is smooth, but it does not seem so economical, and the smell is of concern. I cannot see any visible leaks of fuel, but where should i be checking for this?

 

I use 98ron superunleaded.

 

pop in to your local mot testing station and ask them to check the emmisions. i bet its running far too rich.

 

also check the air filter isnt blocked.

[smckeown 1]

take a look at the plugs

[Rob_the_Sparky 9]

Do you know what engine management it is using? Some are installed using the donor car management (best) others use the original ECU and a dizzy adaptor (not so good).

 

Rob

 

P.S. Idle mixture is not necesarily any indication of whether it is running rich all the time. It can run rich at idle and still have perfect spark plug colour (I know from experience).

 

P.P.S. If using the donor car ECU (motronic) then you should see around 35mpg, from what you are telling us you have ~25mpg. However, it is very hard to be accurate with economy unless you brim the tank each time. Otherwise you may be a fair way out on your guesstimate of economy.

[rocky 0]

Do you know what engine management it is using? Some are installed using the donor car management (best) others use the original ECU and a dizzy adaptor (not so good).

 

Rob

 

P.S. Idle mixture is not necesarily any indication of whether it is running rich all the time. It can run rich at idle and still have perfect spark plug colour (I know from experience).

 

P.P.S. If using the donor car ECU (motronic) then you should see around 35mpg, from what you are telling us you have ~25mpg. However, it is very hard to be accurate with economy unless you brim the tank each time. Otherwise you may be a fair way out on your guesstimate of economy.

 

Thanks for the response guys.

 

My car has the BX16 valve ECU. I will take it to the MOT Testers and see what the emiisons are.

THe air filter is a K&N, and it looks dirty, but doesnt seem blocked, i can hear it 'hissing' ok.

Either way, an estimated 25mpg is not good, so needs to be sorted.

Edited May 18, 2007 by rocky

[rocky 0]

Havent yet taken it for the emissions.

 

But just so i know, what are the adjustments that can be made to stop it running rich?

 

Does the AFM have some sort of screw which can be adjusted, and how effective is this?

[GLPoomobile 958]

I may be wrong, but I don;t think getting the emissions tested at an MOT station will be any good for a diagnosis. It'll only tell you what your emissions are at certain RPM. I think ideally you need to get it on a olling road and get them to check the mixture at the whole rev range and under load.

[James_m 0]

Im also intrested in the screw on the AFM. Does it control idle mixture as per 8v jetronic?

[Rob_the_Sparky 9]

No idea I'm afraid. I expect it is an idle mixture adjust but it could adjust across the range...

[lee-bg 0]

As far as i know you can adjust the CO level from the screw on the debitomer, but only on D6C engine (without catalyst).

Just remove the protective cap and you will see the bolt - but i am afraid for proper tuning you need an exhaust check device to see how the CO varies.

Edited May 23, 2007 by lee-bg

[rocky 0]

But What else can I do to rectify overfueling?

[Scottieb 0]

Fit a Megasquirt?

[Ahl 4]

One thing that hasn't been mentioned here is to try replacing the coolant temp. sensor.

 

These commonly fail on high mileage engines and make the ECU think its cold all of the time, so you get constant overfuelling.

 

You can get them from GSF, not expensive. The part number is on here somewhere.

[Alastairh 47]

Yeah as ahl said a new Ecu temp sensor may well be a good thing anyway.

 

But it can be set up on a mot station emissions machine, have experienced this myself, and theres no need for a megasquirt.

 

Alastair

[rocky 0]

I am not sure what a megasquirt is!

 

My Mi has a cold temp sensor (this is blue top one on the side of the engine block) - i suppose i could change it to a standard temp sensor. Also my fan cuts in when the on the third bar of the water temp gauge (which seems quite early).

Edited May 24, 2007 by rocky

[Richie-Van-GTi 70 2 Cars]

3rd bar on a gti gauge is around 95ish degrees which is not too early at all.

If your swapping the ecu temp sensor only use a direct replacement, they vary resistances across different part numbers and an incorrect one is as bad as using a duff one.

[rocky 0]

Hi richie,

 

Since I have a BX16 valve lump, then this would be the one i need right? I am sure there are not anymore variants of temp sensors for this specific lump?

 

But yes good point, no point getting one with different resistance.

[rocky 0]

Having read many of the previous topics on Mi16's overfuelling, I seem to conclude that smelling fresh petrol fumes when windows are down and driving along is more likely to be a leak of the fuel pipes somwehere under the car or in the engine. (more smell when passenger side window is down).

 

I doubt it is the coolant temp sensor, as mine was new (according to the previous owner). Also, the car idles nicely at 1000rpm so it seems that there arent any issues with idle mixture.

 

Do you think this diagnosis might sound reasonable and how would i test for leaky pipes?

 

I am reluctant to RR test it, if leaky pipes are the problem as RR would not show this.

[rocky 0]

I spoke with my friend today, and he suggested i clean my filter, change rotor arm, change HT leads, and get the timing done.

 

The engine speeds seems to flutter at idle, and it seems the timing is out, thus if i have this done along with the above things, fuelling and general running may improve.

 

How much should i typically pay for timing setup?

[rocky 0]

In My quest to eliminate bits that might affect fueling, i changed the rotor arm, and cleaned out my K&N air filter.

 

However, my car now has a stutter/misfire through the revs, but not at idle?

 

What could this be? does putting on a new rotor arm perhaps exagerate problems with leads (as spark plugs had been changed in Feb, and dissy cap looks good).

[rocky 0]

Hi Guys,

 

When the orange light is dispalyed on the fuel gauge, how many more miles do I have to drive before the tank completely finishes?

 

to me the fuel gaige seems disproportianate. Then again Mi16 power may blur my senses!

Edited June 6, 2007 by rocky

[luggy 13]

Roughly you've got about 5 litres.

[rocky 0]

Ok i changed the rotor arm back to the old one, and misfire seems to have dissappeared, but fuel smell seems greater.

 

I know there are about 6 variants of the bx19 16v rotor arms, but the new rotor arm appears to be the correct one as it looks exactly the same as the old one.

 

This is puzzling me very much why would a new rotor arm and not old one cause a misfire?

[rocky 0]

Just to revisit the topic....

 

I also want to get the overfueling sorted out.

 

I believe i will have to have it rolling road tested, but will the garage be able to tell exactly what is causing the overfuelling, or is it just more guessing? Also on my Mi16 conversion i dont have a clue where the ECU is> so where would it likely be?

 

The reason I ask is because i dont want to pay for the session only for it to not be meaningful. The engine needs a tune i think, shall i have this done before or after roling road?

 

I am so frustrated by my car at the moment. the smell of fuel when it is driven is astonishing.

Edited June 28, 2007 by rocky

[kyepan 291]

you can check the resistance of the HT leads with a multi meter, I think they should have no resistance, if they have resistance they may be breaking down.. somone on here will correct me if this is the wrong way round. and they may also give you the multimeter setting.

 

My mi16 on proper management also smells a bit, and runs a bit rich when its cold. need to get the dizzy and rotor changed also.

 

cheers

 

Justin.