26 replies to this topic

[Bristolmini]

It seemed to all be fine a couple of weeks ago but the car suddenly started running badly. It was just after I changed the oil and had the air filter off.

After running badly for a week I stuck a k&n on and found one of the vacuum pipes had melted so this was replaced. Resetting the stepper motor seemed to help with it idling too.

IT still seems to be running a bit rich though, with noticable black smoke if I floor it and the spark plugs go black quickly.

Any ideas what could be causing this, maybe particular sensors known to cause this kind of problem?

[Bungle]

sprocket is the injection mini man

try a pm to him :wink:

[icklemini]

air leaks...
lambda sensor...
MAP pipe to ecu...

[gsms]

Have you changed/touched your exhaust manifold?

[Bristolmini]

manifolds have not been touched and the MAP pipe to the ecu was the one that was melted and has now been replaced. this seems to have helped a bit.

do lamda sensors die quite suddenly? it was all running OK and then the next day it wasn't.

First injection I have owned and I reckon carbs are so much easier.

[icklemini]

do lamda sensors die quite suddenly? it was all running OK and then the next day it wasn't

oh yeah - can die in all manor of ways..

check all connections etc too...

[Bristolmini]

Is there a way of telling if the Lamda sensor is OK or not? It looks like a right pain to get to because it is on an lcb manifold and is hidden under the inlet assembly and brake servo.

Has a look at as many connections I could see and they all appeared fine. Might be worth taking them all apart and cleaning them up anyway though

[Pandora]

Try the vacum pipe that was a problem for me. As the ecu thinks its not there or see's thats theres not enough, it will add more fuel and make it run rich just check all air and other pipes.

[pikey7]

This worked on my other car, but I'm not sure on the Minis ECU function. Give it a go anyway, it can't hurt!.......

If you disconnect the Lambda sensor and see if the engine runs OK, then It'll be a failed sensor! The sensor itself is very difficult to check as a standalone item. I think you can do it with specialised equipment (If you own Bosch!).....

They are *only* used for fine tuning and keeping emissions down by feeding back to the ECU to adjust fuel/timing. On my Other car, I've completely removed it, and fitted a wide band unit in its place (for tuning!)

[The Roadie]

Try the vacum pipe that was a problem for me. As the ecu thinks its not there or see's thats theres not enough, it will add more fuel and make it run rich just check all air and other pipes.

This seems to be a common problem. Mine did this, it ran rich for ages before it finally collapsed though, seems the pipe perishes with age.
Also my friends SPI Cooper is also starting to run quite rich.

[icklemini]

Yes you can test the output from the lambda with either an accurate volt meter, or a code reader, etc.

It should oscillate its voltage from around 0.3 to 0.8v and does this *constantly* - its pretty much the only thing that can tell the ecu whats coming out the engine and fundamental to the operation of the injection system

can be tested off the car with the help of a blow lamp to give it some heat!!



As i said before though - check all connections, check for any blockages, rusty bits, etc..

TTFN,
Dave

[Bristolmini]

The lamda sensor may be worth a look at the, might have to wait till the weekend for that as it seems to be dark when I get home from work at the moment

[Sprocket]

I have only ever experienced problems with lean fueling, but could hazzard a guess as to your problem knowing how the fueling is controlled.

A leaking manifold can cause air to be drawn into the exhaust system by venturi effect. This results in extra oxygen that the oxygen sensor detects. The result is the ecu adds more fuel as it thinks the engine is running lean. My thought on this is that it is the least likely thing to happen, but still worth checking the manifold for tightness and the down pipe flange too. Anything further down stream wont bear any effect.

Another thing to cause rich fueling is the inlet air temp sensor. It may be reading a number of degrees Centigrade colder than it actualy is ( higher resistance). It does not need to have failed totaly and will cause the ECU to add more fuel thinking the air is more dense than it actualy is. This is the green sensor under the filter housing. The only real way to check this is with a diagnostic and the use of a calibrated thermometer. This is what those power boost for a fiver scams are all about that you see more and more of. Its basicaly a resitor in parallel with the thermistor (varialble resistor by temperature). This changes the over all resistance and fools the ECU into thinking the air is colder and a lot denser than it actualy is, so, it adds a sh*t more fuel. I wouid start with this sensor first, but if it has been running rich for a while the oxygen sensor may be buggered any way as its contaminated with carbon deposits which clogg the pours. And no it wont get better if you manage to fix the initial problem, you have to replace it.

The oxygen sensor can become sluggish and cause all sorts of problems with the fueling rich or lean, and is the first thing I would change unless you know that it is in good working order ,or, is obvious that it has not been changed in a long while. Testing the sensor can only be done satisfactoraly with a diagnostic which can read the high transient rate of the voltage produced which in itself is only between 200 and 600 millivolts (0.2 to 0.6 volts) and changes roughly every tenth of a second. This means you cannot measure it with a volt meter as its response rate will not be fast enough.

http://www.picotech....bda_sensor.html

Oxygen sensor should only be replaced with the original direct replacement Bosch item and will cost around 60 notes from a bosch dealer, any where else is just rip off prices. Find your nearest dealer here http://www.boschauto...oduct&intType=1 and the part number is 0258 003 193

Make sure you are using the correct plugs, it does realy make a differnce on the injection cars for some reason. They are NGK BPR6ES

To get the oxygen sensor out of the manifold you will need the crow foot type oxy sensor socket. The standard one that looks like a spark plug socket does not work. There is limited space, you cant get a spanner to it or fit an extention for the ratchet either. The crow foot works. If the sensor is showing no signs of budging then you will at least have to remove the inlet manifold to get a good size spanner on it with a lot of leverage.

Crow foot spanner for oxygen sensor http://www.cats-dire...bda-sensors.php Its the one at the very bottom. And shy away from the universal sensors :cheese:

[Bristolmini]

from the picotech site:

'As the sensor ages, it becomes sluggish. Eventually it produces an unchanging signal or no signal at all. When this happens, the Check Engine Light may come on, and the engine may experience drivability problems caused by an overly rich fuel condition. Poor fuel economy, elevated CO and HC emissions, poor idle, and/or hesitation during acceleration are typical complaints.'

Sounds exactly like the problems I am experiencing so a good place to start. As I have no way of testing the lamda sensor then it may be worth replacing it anyway if I am taking it apart. I don't know how long the current one has been there so it may well be past it's best

[icklemini]

You can test them with a (decent) multimeter.. and off the car you can test the sensor with a blow lamp...brutal but shows it switching...

Get a diag session done on it (shame you're not that local to me)...
and certainly go for the OEM lambda - avoid the aftermarket ebay specials..

TTFN,
Dave