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MG MGF Technical - MEMS Error - Any Ideas?

Hello everybody,

My 98 MK1 VVC failed its MOT a couple of weeks ago with the key problem being Emissions. :(

The garage has been F-ing around with it for 2 weeks now and they don't know whats wrong. Apparently the ECU was full of errors, so they cleared them down and gave it back to me to drive round for 2 days to see what gets logged.

Their auto electrician has told me the error "Clamp Lock Disabled" was logged but no-one knows what it means. Anyone out there who can help?


Nick Atkins

When my 2000 vvc failed it's MOT on emmisions the Lambda sensor had failed. Can't help with the error code.
Stuart Elliot

The Lamda sensor was replaced with a pattern one last year when it failed the emissions as well!

Nick Atkins

No idea what "Clamp Lock Disabled" means either. The folks with access to Testbook might be able to furnish us with some clues.

I wonder whether there is a possibility here that MEMS is recording a whole host of random errors due to a short/ dry solder joint/ poor earth?

Does you garage have access to a 'spare' MEMS to see whether this solves the emissions issue?
Rob Bell

I guess they have been running the "Test-Book"without the current clamp sensor around the battery cable.This will be highlighted on the screen. In this mode only a very few parameters are possible to read.
The current clamp reads every tiny load on the battery to the computer,i.e. can determine if the window motors are even the slightest stuck,injector dead time etc.etc. /Carl.

Do you have the numbers for the failed emission?
These will point in the direction of where the trouble can be. Even the smallest leak on the system will upset the readings,had to re-new the SS-seals at the catalyst on mine in order to pass the test.... /Carl.

>> Even the smallest leak on the system will upset the readings,had to re-new the SS-seals at the catalyst on mine in order to pass the test.... <<

Does a leak ruin the Lambda reading Carl?
Rob Bell

No because the gas under pressure blows out. Only if air gets in it would not read correctly.
Stuart Elliot

Carl - That current clamp you mentioned sounds about right because I know these guys were fumbling around like Muppets and didn't have a clue what they were doing!

My Emmissions report shows:

Catalyst equipped vehicle with closed loop control
Engine Oil Temp: 70 degrees C

Fast Idle Test:
CO - 2.74%vol (Should be <0.3%)
HC - 177ppm (Should be <200ppm)
Lambda - 0.92 (Should be 0.95-1.09)

2nd Fast Idle Test:
CO - 1.96%vol (Should be <0.3%)
HC - 142ppm (Should be <200ppm)
Lambda - 0.94 (Should be 0.95-1.09)

Natural Idle Test:
CO - 0.50%vol (Should be <0.5%)

What do you guys think?

Thanks in advance... :)

Nick Atkins

To Rob and Stuart;

The MoT (at least over here!) does use a separate gas tester in the exthaust outlet. Due to the pulsating nature of the combustion there is varying pressure in the exthaust system. A leak in the flexi or further down at the catalyst joints will upset the reading.The cars own lamda sonde will of course NOT react on any leake further down the system .
Been there , done that. My own fault as I change back to cat-pipe after every MoT ;O).
Nick, on the move at the moment, will respond back as soon as i have acess to files at home (monday) /Carl.

Forgot to mention the most likely errors that could give the numbers you shown.
The engine is going "rich", i.e lambda low=too much petrol,too little air.Possibly faults are bad ignition cables /old plugs and/or clogged airfilter.
The high HC is partly from above and also possibly oil leaking into the cylinders (worn valve-guides,pistons etc.) or petrol in the oil,dilution due to frequent cold-starts and short runs. High milage car ?
It would be easy for the guys with the Test-book to determine if either the lambda sensor or catalyst were shot if they could handle the system ;O).
A trick to get you thru MoT, but not a permanent fix is to fill an almost empty tank with no less than 1 liter carb. alcohol and drive directly to the test center. Afterwards refill with ordinary petrol to full tank. BR, Carl.

PS. Do you have "E85" ,15%alcohol and 85% petrol in U.K ? It is a known cure to emission problems on high milage cars...

Stuart, Carl, thanks. :o)
Rob Bell

This thread was discussed between 02/03/2006 and 05/03/2006

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