Emmisions help

[Vauxste]

Hi Guys

Need your expert help. 350i had its emmisions checked today. At tickover CO was reading 7.51 and at 2000 rpm it was reading 1.51 - can anyone point me in the right direction as to what it might be.

Thanks

[peaktorque]

Vauxste said:

Hi Guys

Need your expert help. 350i had its emmisions checked today. At tickover CO was reading 7.51 and at 2000 rpm it was reading 1.51 - can anyone point me in the right direction as to what it might be.

Thanks

Air-flow meter, air leak after AFM, dodgy coolant temperature sensor, mad ECU...........

[Vauxste]

Thanks for that - pipe between AFM and plenum is a bit old amd looks like it might be problem - will try and source another one before I do anything else

[adam quantrill]

Air leak after AFM would make it lean, not rich. Engine temp sensor is uaully a goodun. Could be crud in the bypass on the AFM.

[Vauxste]

Hi Adam - if it was the temp sensor would it not do it across the rev range. Also were is the bypass on the AFM is it a pipe or a drilling in the unit itself

[peaktorque]

adam quantrill said:

Air leak after AFM would make it lean, not rich.

that's true!

[adam quantrill]

>> Hi Adam - if it was the temp sensor would it not do it across the rev range

Oh yes it would! Been there....

Only time it won't be that rich is on wide open throttle, but I bet you haven't measured that, unless you have a rolling road handy. Another possiblity is the fuel pressure too high - if the regulator isn't doing its job or the return pipe is blocked.

[rev-erend]

Are you sure the HC was not high too..

A high co suggests a rich mixture.

[Vauxste]

Hi guys

First of all Thanks to you all for your help. Have not had time to look at it yet, probably the weekend. In answer to the HC being high - yes it was. At tickover readings are CO=7.51% HC=320ppm

At 2000rpm CO = 1.62 HC =104ppm

Interesting reply to a latest thread about rich running with the fuel return pipe being crimped. Would this cause an over pressure of fuel being forced into injector rail at tickover with a pressure drop when engine revs higher causing the difference in my figures. Suppose the fuel regulater could be at fault as well.
Any ideas gratefully recieved

Many Thanks Guys

Steve

[350zwelgje]

As mentioned by Adam, crud in the AFM bypass seems likely and would be my first thing to look at (based on previous experience).
The straighforward solution would be then: Take the CO-adjuster completely out and clean it.
During having these type of same issues, it was also difficult to adjust the idle rpm. Clean the CO-adjuster solved high CO and not being able to adjust idle in one go.

Rob

[Vauxste]

Thanks Rob that will be my first job when I get round to it. When screwing adjuster in I could not get it to tickover - so out it will come and will clean it

Thanks

Steve

[rev-erend]

The reason I ask about HC - is that it indicates that something is broken / fouled / ign breakdown etc etc..

CO being slightly high just needs a tweeking of the co mixture screw..