Running rich

Wed Aug 30, 2017 11:41 pm

Hey guys . My m20 has always ran rich . I have changed the afm meter all the intake hoses are new . New coolant temp sensor also replaced . I am running a Bosch 173 ecu and have noticed I haven't got a lambda sensor . I know I have the plug for one under the front battery tray. I have the standard cast iron manifold and a complete scorpion stainless steel exhaust system . I have no boss on this system for a lambda sensor . My car was originally a 320i but converted to a 325i sport m20 b25 . Has the 173 ecu pre programmed for a lambda sensor ? If so I'm hoping to fit a lambda sensor into my exhaust system . Only problem I have is that the exhaust system is double right the way though to the mid section to the back box . There is no cross over section for me to get the lambda sensor mounted to gain both readings . Should this be a problem if I had it welded in to one of the pipes? Thanks

Thu Aug 31, 2017 12:20 am

173 ECU and later M20 ECUs don't need a lambda sensor for it to fuel the engine properly. They automatically substitutes a default lambda sensor value when one isn't connected. The four cylinder M40 ECUs need a externally supplied signal.
The purpose of a lambda sensor, when fitted to an engine, is to protect a catalyser against damage caused by a fault resulting in a rich mixture, rather than to make the engine run properly.
If fitted into one downpipe, it would only detect an incorrect mixture from one of the three cylinders feeding that pipe, but that's not a problem with a properly running engine.
What makes you think your car is running rich? Both lean running and rich running will result in a fuel smell from the exhaust, and lean running is more common than rich running.

Thu Aug 31, 2017 9:09 am

Brianmoooore wrote:173 ECU and later M20 ECUs don't need a lambda sensor for it to fuel the engine properly. They automatically substitutes a default lambda sensor value when one isn't connected. The four cylinder M40 ECUs need a externally supplied signal.
The purpose of a lambda sensor, when fitted to an engine, is to protect a catalyser against damage caused by a fault resulting in a rich mixture, rather than to make the engine run properly.
If fitted into one downpipe, it would only detect an incorrect mixture from one of the three cylinders feeding that pipe, but that's not a problem with a properly running engine.
What makes you think your car is running rich? Both lean running and rich running will result in a fuel smell from the exhaust, and lean running is more common than rich running.

Smells of fuel when driving with roof down when car is at idle it's quite strong . Eyes can start to sting . I have bought a lambda sensor thinking this could change the fuel air mixture .take it it's a waste of time . Confused . Car is very quick no lack in power just smells a bit . Was looking into miller maf convertion is that a waste of time and money ?

Thu Aug 31, 2017 9:56 am

No Miller MAF conversion or other snake oil solutions required. The management system controlled the fueling perfectly adequately when the car left the factory, so all that is required is to return it to that condition now.
The solution will probably turn out to be very simple and cheap - it's just a matter of finding what that solution is.
The first thing we need to establish, is whether the engine is running rich, lean, or neither, and for that we'll need to know the colour of the tip of at least one spark plug, preferably all, and preferably pics. of them.
Are you sure you don't just have a simple weep from the high pressure fuel line in the engine bay, or elsewhere? Are you sure the smell originates from the exhaust?

Thu Aug 31, 2017 11:16 am

Brianmoooore wrote:No Miller MAF conversion or other snake oil solutions required. The management system controlled the fueling perfectly adequately when the car left the factory, so all that is required is to return it to that condition now.
The solution will probably turn out to be very simple and cheap - it's just a matter of finding what that solution is.
The first thing we need to establish, is whether the engine is running rich, lean, or neither, and for that we'll need to know the colour of the tip of at least one spark plug, preferably all, and preferably pics. of them.
Are you sure you don't just have a simple weep from the high pressure fuel line in the engine bay, or elsewhere? Are you sure the smell originates from the exhaust?

Smell is defiantly coming from the exhaust . I will remove spark plugs and check . Was thinking back to when I did the b25 convertion from the b20 . When I bought the engine it never had the throttle body and intake boot or air box . I had removed the one from the m20 and swapped them over to the b25 . I was just comparing the part numbers on real oem and part numbers are different. So I might just buy the m20 b25 throttle body and fit that as well as replacing the b20 intake book as I beleave that is also different.

Thu Aug 31, 2017 12:14 pm

If you're using a b20 throttle body and intake boot on a b25 that certainly isn't going to help matters.

Thu Aug 31, 2017 1:30 pm

Cloggy Saint wrote:If you're using a b20 throttle body and intake boot on a b25 that certainly isn't going to help matters.

Not going to affect the mixture strength, though. Just the same as driving with the drivers floor mat doubled up under the accelerator pedal.

Thu Aug 31, 2017 4:36 pm

Brianmoooore wrote:
Cloggy Saint wrote:If you're using a b20 throttle body and intake boot on a b25 that certainly isn't going to help matters.
Not going to affect the mixture strength, though. Just the same as driving with the drivers floor mat doubled up under the accelerator pedal.

At the time of the transplant I didn't have the correct throttle body
So I removed the one of the 320 . I will replace that with a 325i and see where we are at . It's a shame because I love my car . I have had it 9 years now . May change the fuel filter also .

Thu Aug 31, 2017 4:48 pm

Is the fat breather rubber pipe from yer fuel tank to the filler good? Usually creates a massive fuel stench at the rear end if fractured/perished.

Just a thought

Paul

Thu Aug 31, 2017 5:36 pm

paultv wrote:Is the fat breather rubber pipe from yer fuel tank to the filler good? Usually creates a massive fuel stench at the rear end if fractured/perished.

Just a thought

Paul

Hi Paul will check .thanks

Thu Aug 31, 2017 5:41 pm

what colour are the injectors and when were they last overhauled?

Fri Sep 01, 2017 8:23 am

aimlessrock wrote:what colour are the injectors and when were they last overhauled?

The injectors are the original 325i ones . I remember checking the part numbers on them when I replaced the o rings after getting the manifold powdercoated

Fri Sep 01, 2017 9:33 am

Still awaiting the spark plug tip data! Until we have that, and have an indication of whether the car is running weak or rich, everything is just speculation and guesswork.
Weak is the most likely, since with a weak mixture, totally unburnt fuel can pass though the exhaust system. With a moderately rich mixture, all the fuel tends to get broken down, but the lack of sufficient oxygen results in incomplete combustion, leaking excess atoms of carbon (=soot) and large quantities of CO in place of CO2.

Fri Sep 01, 2017 1:38 pm

Brianmoooore wrote:Still awaiting the spark plug tip data! Until we have that, and have an indication of whether the car is running weak or rich, everything is just speculation and guesswork.
Weak is the most likely, since with a weak mixture, totally unburnt fuel can pass though the exhaust system. With a moderately rich mixture, all the fuel tends to get broken down, but the lack of sufficient oxygen results in incomplete combustion, leaking excess atoms of carbon (=soot) and large quantities of CO in place of CO2.

Will get to my lock up tonight hopefully and will take pics . Cheers Brian