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MOT Problem Help Please


linky1967
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linky1967

Hi,

I would really appreciate some help as I've just tried to put the car for an MOT and the guy had to give up on the omission test

 

1. lambda reading was too high, although HC and C02 where OK

2. engine overheated as the fan didn't cut in

3. engine started to miss-fire

 

I had a problem before with the thermo fan, but I thought I fixed it (poor connections). I think the switch is at fault - but can any one tell me how to get the correct replacement?

 

Lambda - too high

could this be related to  miss-fire or is it an ecu or lambda sensor itself

 

Where can I get a new sensor and how much do they cost?

 

20XE engine

MBE941 ecu

wide band lambda sensor

 

Any help will be greatly appreciated

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- by the same token, if there is a tiny bit of excess movement, but no real wear, then sometimes the bearing just needs a bit of adjustment. Note though, that cause of how the castellated nut is secur

Refer your tester to the following documents...   https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/346222/emissions_17th_edition.pdf this one contains the text Q plated veh

Alternatively if you hold the foot brake on (an assistant or a bar on the pedal) or apply the park brake, then rock the wheel with your hands in the 12 and 6 positions on the wheel, any wheel bearing

Welly Jen

The high lambda value is being measured by the garages sensor, not the wide band sensor on your car. Unless your sensor is correcting the fueling on your ecu it is unlikely that a faulty wide band sensor is causing this. Depends on how your MBE ECU is set up and this would need a laptop connected to determine.

The fan switch is probably a standard M22 fitting. They do fail. The switch on temperature you'll need depends on the engine type and the thermostat on/off temperature. A search of the forums should come across some recommendations for your engine.

No answers from me I'm afraid. Suggest the order to fix things is to get the fan working reliably first, then track down and fix the misfire, then take it back and see if the lambda value is still too high.

Jen

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Dave Eastwood (Gadgetman) - Club Secretary

im presuming your car has throttle bodies and fuel injection?

The wide and lambda sensor, what does it connect too? A display, a blank control box, with a connection to the ecu? Or something else...

Daft question, but do you have a year plate registration or a Q? (And does the Mot centre know kit cars?)

Did the misfire happen before or after the over heating?

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If it was getting very hot the fuel could have been vaporizing and causing the misfire

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linky1967

im presuming your car has throttle bodies and fuel injection?

The wide and lambda sensor, what does it connect too? A display, a blank control box, with a connection to the ecu? Or something else...

Daft question, but do you have a year plate registration or a Q? (And does the Mot centre know kit cars?)

Did the misfire happen before or after the over heating?

Hi

Yes SBD throttle bodies and injection

 

As far as I can see, it connects into the main loom coming from the ecu

 

Q plate (registered 1997) - not too sure of their kit car experience, although he did question the stick on number plate over the nose cone, stating that it should be upright. He started to look on the internet for other examples!

 

I never noticed the misfire before to be honest.  Its nothing too heavy, more of a light flutter or a missed beat, but Its does seem to remain through the rev range

 

However, when hot and taking my foot off the throttle I get it popping back quite bad. When cold there is not popping back. I've been told this is a weak mixture easy when the throttle is shut off.

 

Over heating - I think I've fixed this, it looks like a faulty relay. I'll swap this tomorrow

 

Cheers

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linky1967

The high lambda value is being measured by the garages sensor, not the wide band sensor on your car. Unless your sensor is correcting the fueling on your ecu it is unlikely that a faulty wide band sensor is causing this. Depends on how your MBE ECU is set up and this would need a laptop connected to determine.

The fan switch is probably a standard M22 fitting. They do fail. The switch on temperature you'll need depends on the engine type and the thermostat on/off temperature. A search of the forums should come across some recommendations for your engine.

No answers from me I'm afraid. Suggest the order to fix things is to get the fan working reliably first, then track down and fix the misfire, then take it back and see if the lambda value is still too high.

Jen

Thanks, 

I downloaded the software for my MBE941 from SBD. I've got an old laptop and fitted it with PCMCIA serial port. it connects up OK and recognises the ecu but the data it shows is garbage for the most part - as you can see from the photos. 

 

It doesn't help that I don't know what I'm really doing either, so if you have any tips please send let me know. Thanks

 

20160608_174429558_iOS_zpshsp6qcn3.jpg20160608_174437223_iOS_zpsgorv1xr7.jpg

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Terry Everall - WSCC Competition Secretary

If its a Q plate why are they testing the emissions?

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linky1967

If its a Q plate why are they testing the emissions?

 

I thought all cars had the test, but the limits were different on older ones. Are Q plates exempt then?

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Dave Eastwood (Gadgetman) - Club Secretary

For many parts of the test a Q plate car is to be treated the same as a car made before 74 and in some cases 71.

Normally, for emissions, it's to be treated as visible smoke only. There is no test done with measuring apparatus.

On the misfire I'm not sure if I follow you, are you saying it's still doing it, (all be it intermittently) even though the car has cooled?

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linky1967

For many parts of the test a Q plate car is to be treated the same as a car made before 74 and in some cases 71.

Normally, for emissions, it's to be treated as visible smoke only. There is no test done with measuring apparatus.

On the misfire I'm not sure if I follow you, are you saying it's still doing it, (all be it intermittently) even though the car has cooled?

The misfire is more noticeable when hot and seems consistent up the rev range. I even changed the plugs and its still the same

 

The popping back through the exhaust only occurs when hot, or warmed up and only happens when I take my foot off the pedal. I was told its because its running weak. I don't get any popping back when the engine is cold

 

I hope that explains it better

Thanks

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Refer your tester to the following documents...

 

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/346222/emissions_17th_edition.pdf

this one contains the text Q plated vehicles are to be treated as being first used before 1 August 1975 for emissions purposes.

 

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/518634/mot-inspection-manual-for-class-3-4-5-and-7-vehicles.pdf  

This one contains the text Vehicles having a Q plate registration when presented for MOT are to be treated as follows: 
For emission purposes only, all these types are to be considered as vehicles first used before 1 August 1975

.

 

Both documents also contain the following text:

 

"For emissions purposes only, kit cars and amateur built vehicles first used before 1 August 1998 and w**kel rotary-engined vehicles first used before 1 August 1987are to be considered as first used before 1 August 1975"

 

In both cases the test is "assess the smoke emitted from the tailpipe , at idle and at 2500 rpm.

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Terry Everall - WSCC Competition Secretary

Popping is usually down to unburnt fuel being ignited in the exhaust system and not due to a weak mixture

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Trevturtle

Thanks,

I downloaded the software for my MBE941 from SBD. I've got an old laptop and fitted it with PCMCIA serial port. it connects up OK and recognises the ecu but the data it shows is garbage for the most part - as you can see from the photos.

It doesn't help that I don't know what I'm really doing either, so if you have any tips please send let me know. Thanks

20160608_174429558_iOS_zpshsp6qcn3.jpg20160608_174437223_iOS_zpsgorv1xr7.jpg

The mbe software will show garbage because you need to load the configuration file to match your ecu . The configuration file acts as a translater. Use the wrong one or don't load one usually means garbage.

Give me a call I will talk you through it

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Martyn Vann - Warwickshire AO

Refer your tester to the following documents...

 

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/346222/emissions_17th_edition.pdf

this one contains the text Q plated vehicles are to be treated as being first used before 1 August 1975 for emissions purposes.

 

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/518634/mot-inspection-manual-for-class-3-4-5-and-7-vehicles.pdf  

This one contains the text Vehicles having a Q plate registration when presented for MOT are to be treated as follows: 

For emission purposes only, all these types are to be considered as vehicles first used before 1 August 1975

.

 

Both documents also contain the following text:

 

"For emissions purposes only, kit cars and amateur built vehicles first used before 1 August 1998 and w**kel rotary-engined vehicles first used before 1 August 1987are to be considered as first used before 1 August 1975"

 

In both cases the test is "assess the smoke emitted from the tailpipe , at idle and at 2500 rpm.

 

As above, the MoT tester MUST follow the guidance in the manual! If the emissions test is the only reason for your MoT fail then you should request that a certificate be issued based on the correct test procedure. The station should contact DVSA to amend the original certificate as they issued it in error but they are unlikely to want to do so as it may affect their risk rating. If you are happy to have the fail on your car's online record then just take the re-test certificate, your choice.

 

Obviously any misfire or overheated needs to be sorted but at least it does not prevent the issue of an MoT certificate.

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