7 replies to this topic

[miniboy1971]

I have an S-Works MPi that has failed its MOT on the emissions - see my earlier post.

The MOT tester would appear to have tried a number of times to get it through, but despite getting the HC and CO levels down to acceptable levels, he could not get the Oxygen level down – it was 1.12%

I’ve just had a diagnostic check done using a Snap-On unit and it has given the following fault codes.

5 Ambient Air Sensor Short to Ground
25 Ambient Air Sensor

13 Oil Temperature Circuit Volts too high
23 Oil Temperature Circuit Sensor Circuit

11 Internal ECM Volts too high

44 Feedback disabled on clamp

The ambient temperature is reading minus 213. I've had this particular fault code a few years ago and subsequently replaced the sensor. But it's back !

There was also a code 10 indicating Battery Volts Low, but this was an old code caused by a dodgy battery that was replaced within the last month. This was cleared off ok.

The exhaust system is holding pressure and the Lambda sensor tested ok.

Does anyone have any experience on what would be causing all these fault codes and are they related ?

Cheers all.

[sirweste]

My MPi is at MLMotorsport this week, the autoelectrician that repairs the electrics and ecu's is due in to fix it at somepoint this week. It would be a good oportunity to get you seen quickly. I had similar error codes on mine a while back, tested everything i could and had to conclude it was a ecu problem, at the time i couldnt afford the repair and as it got through the mot by 0.01 i left it - until now.

[miniboy1971]

Thanks for the tip off !!

Funnily enough I was going to give them a call today to see if they could give me any advice. Hope yours gets sorted. Finger crossed on mine.

Would still welcome feedback from others with similar experiences....

[Sprocket]

That code 11 looks worrying

Code 5 and 25. If the air temp sensor is open circuit, it will be throwing fuel in there. Much the same way it will if its shorted. The reason for this is that as the ari gets colder it gets denser, as it gets denser it contains more oxygen, so the temp sensor tells the ECU the air temp, where it can then add more fuel to compensate, keeping the base fuel tables correct. Obviously when the air is warmer there it is less dense and there fore less oxygen so the ecu will start to remove fuel. However! there will be a point where the ECU decided to richen the fueling back up again to try and cool the engine down in extremes of inlet air temps. If the sensor is out of limits the ECU will assume, rightly or wrongly a temperature.

So, you have two extremes that could cause this problem dead short would indicate a high temp and open circuit would indicate an extreme low temperature.

Check the sensor and its wiring!!

The oil temp sensor is also a little worying. Make sure you have the correct plug on the connector as the oil pressure switch is the same plug. Be very carefull as to which wire you plug into which connector!! oil pressure switch is a single wire white/brown and 12v, the oil temp sensor is two wires and 5v, the two do not mix!!! crossed connectors here could result in the code 11, but could also seriously damage the ECU.

Have you tested the lambda sensor yet? is the voltage stuck low? or does it swing high-low?

If the lamda sensor tested ok then there is only one conclusion, the exhaust is leaking. Think about it this way. If the lamda sensor is swinging high-low, the ECU is controlling the fueling to exactly what it should be, but where has the excess oxygen come from. At idle the fueling is lambda 1 the lambda sensor sings the voltage high-low above and bellow this point, therefore if the lambda sensor is working, the engine is operating as it should. You need to look for other areas where oxygen can enter the exhaust. A missfire would give a high HC ppm, but yours is almost nill. The cat may be converting it out you say? well no, an engine without a cat will produce around 200ppm of HC. if the engine missfires the HC's go through the roof. Fit the cat and that 200ppm soon becomes close to zero 15 or 20ppm perhaps but the missfire would show up as a much higher reading, hense why the limit is 200ppm.

I still think you will find a pin hole some where, or a joint that is not qite sealed. It only needs a small hole. Check for corrosion around the welds of the backbox, the joints of the 'y' piece on any LCB. That oxygen has to be coming from some where if your lamda sensor is working correctly

[miniboy1971]

Thanks for that Sprocket.

I've decided to take the car into ML Motorsport and, together with all this information, hope that I'll get it sorted.

I'll let you all know what happens.

Cheers.

[miniboy1971]

Update for those interested !!

All the fault codes have been cleared except the first two groups associated with ambient air and oil temperature. I'm told that you can't clear these as the ECU is trying to find sensors that aren't on the Mini - presumably a throw back to the MGF which I understand this ECU was also used for.

I took the car into ML Motorsport today and Andy done a compression test which was all OK.

Andy commented that the high lift rockers didn't sound as 'rattly' as they normally do, which could mean the gaps are a bit too 'tight', which would effect the emissions.

He checked over the exhaust system, manifold, etc and could not find any leaks.

After a few other checks and a quick jump on the gas analyser, Andy concluded that I need to replace the Lambda Sensor, adjust the tappets and also change the spark plugs back to standard and not use the ones recommended for the S-works kit.

Andy's going to sort this all out for me mid-end of next week, so I'll let you know how it all goes.......fingers crossed

[miniboy1971]

IT'S PASSED THE MOT.....YIPPEE...!!!!!

The new lambda sensor, changing spark plugs back to standard and slight adjustment on a couple of the tappets has done the trick.

BIG thank you to Andy at ML Motorsport, Minidaves for coming round to do the diagnostics and Sprocket for advice.

Car is running sweet as a nut...!!! Well chuffed....!!

[Sprocket]

Good to hear