78 replies to this topic

[pete l]

Hi all,

 

My MPI failed it's French MOT on emisions.

 

It is giving 1.03% on tick over and 1.32% on fast idle.

 

Now this doesn't mean much to me but it might to someone out there reading this.

 

Any ideas what needs to be changed ? or tested etc.

 

Heres a clip of the car on T4

 

 

Any help appeciated.

 

Thanks.

 

Pete.

 

 

[Bat]

Hi,

I'm reasonably sure you shouldn't be seeing any 3v readings from the lambda sensor, but that may just be the T4

The MOT in this country uses a 4 gas analyser, assuming the French do the same what are the other 3 please?

Cheers 

[pete l]

The only other thing that is tested is lambda which is at 1.069 but should be between 0.97 and 1.030. Again, I have no idea what that means

[pete l]

Most sensors have been changed for new ones.

MAP sensor,

Coolant

Manifold temp

I tried a new oxygen sensor from minispares but that didn't even work with the T4. So i put the old one back in.

[Steve220]

You should only be getting a max voltage of 1.0 if I remember. Looks almost wired up wrong or broken.

[pete l]

I have had some weird wiring with this car, but what makes you think the lambda is wired up wrong ?

[r3k1355]

because the voltage is all over the shop at idle.

 

How are they getting the manifold pressure and coolant temp reading?

[pete l]

But that is what lambda sensors do, up and down all the time.
And the readings are from the T4, the MG Rover diagnostic equipment that all garages had.

[Bat]

Hi,

It would appear to be running rich, given the co% reading.

Ideally you could do with getting a 4 gas print out from the machine rather than the MOT result as that may help you in the right direction.

Have you checked for vacuum leaks and try removing the vac pipe from the pressure regulator see if there's any fuel coming out.

Any leaks in the exhaust system or manifold gaskets?

Cheers 

[pete l]

hI Bat,

 

I've asked around to see if anyone I know has a 4 gas reader and can't find one.

 

I have checked for vacuum leaks, the only thing I can see that doesn't seal is the rocker cover filler cap.

 

I have a new fuel pump as the other one packed up, it's a minispares universal one that sounds rough, I haven't checked to see if the return is blocked in any way, I will this weekend. 

 

Exhaust and gaskets seem to be leak free, but how do I test to make 100% sure ? would a tiny miniscule leak cause this ?

[Bat]

Hi,

Air getting in will cause the lambda sensor to think the mixture is weak and add more fuel.

The MOT station machine should be able to give you a 4 gas print out, if they know how to work it!

I'm not telling you to rip the exhaust apart or do anything else as at the moment we've not established what the the problem is.

Take a look for signs of leakage, you may be able to get a smoke test done if there's suck a thing for exhausts?

The fact the new lamdba didn't work may be worth investigating, does the wiring on the car l like it's been altered? 

Cheers 

[pete l]

There were only 2 readings on the emision tester.

 

The new lambda didn't work but the old one does, it might be way out but it is "working" which to me means there is nothing wrong with the wiring.

[pete l]

I have a new original BOSCH lambda on it's way.

[Bat]

Hi,

It is working but the 3v spikes is what makes me wonder if there's some wiring shorting together or to ground, maybe you disturbed it and that's why the new sensor didn't work?

I knkk it's a long shot but it's often the obscure things that are the fault...

Cheers 

[pete l]

Hi,

 

i'm getting over 3 volt spikes I agree, but I'm also getting 0.2 volt spikes, I don't think a short somewhere would allow the volts to drop that low.

 

I'll let you know what the new lambda does, should get it tomorrow.