M

Mike Mayberry

New Member
I have a disco 2 4.0l V8; reconditioned engine put in a month ago and failed the MOT due to emissions. Computer showed codes for the MAF and both pre cat Lambda sensors; all have now been changed but emissions still too high.

Fast Idle Test
CO 3.82% Fail
HC 137ppm Pass
odd squiggly thing 0.918 Fail

2nd Idle Test
CO 3.72% Fail
HC 129ppm Pass
0.902 Fail

Natural Idle
CO 4.48% Fail

Garage says it's running too rich and the ECU might need reprogramming for the new engine.

Does that sound right? Who's best for this, a LR dealer?

Thanks in advance.
 
Last edited:
ƛ is odd squggly thing? Thats lambda, detects the oxygen in the exhaust, and from that determines the air/fuel ratio. Many things other than MAF can screw this up, from a simple air leak right on to a completely fubared injection system

An ecu should not need reprogramming unless it is a vastly different engine.
 
Seffy said:
ƛ is odd squggly thing?
Click to expand...

Yes. :)

Seffy said:
An ecu should not need reprogramming unless it is a vastly different engine.
Click to expand...

That's what I thought. It's replaced the 4.0l V8 I cooked the heads on back in January. It's LPG converted but the results are the same on both petrol and LPG. I figure if we can get the petrol right the LPG will be fine.

Seffy said:
...a simple air leak...
Click to expand...

Suggested that to them last week and they've said there aren't any.

This engine has only done 323 miles; Romford to Goodwick then the garage and back for the MOT.
 
Different fuel systems wil;l need setting individually, it failed em iss ions on LPG or Petrol?
L:pG burns much cleaner and usually does not use your petrol ECU

Are all the Lambda sensors working correctly that's usually one of the common components between the systems.
 
I only have one set of figures but they said it was the same on the LPG; high CO.

As far as I know the Lambda sensors are working. They have been replaced; the others had only been in a year and 6 months of that it was standing waiting for the engine change.
 
"Lambda's sensors are working" does that include the engine management ecu receiving their info.
 
You need to hook up some diagnostic kit and see if the Lambdas are toggling up and down as they should.

Hawkeye or Nanocom will do it.

Once you have confirmed they are or are not working, you can go on to the next item, but they are pretty much the centre of the engine management sensors.

ECU shouldn't need touching as others have said.

Peter
 
Actually the fuel trims should have been reset when the new engine was fitted,plus a check of all the sensor readings to check its running closed loop and the fuel trims are in the parish. It could be as simple as partial misfires caused by failing plug leads,often not easy to detect on a smooth v8. Whoever fitted the engine ought to be responsible for these checks,or any possible warranty claims will be out of the window...
 
The LPG ecu only piggybacks the output from the petrol ecu,so if the long term adaptions of the petrol ecu are miles out,then so will the LPG ones. If the trims are too far out it won't be possible for the oxygen sensors to switch properly anyway,the whole thing needs to be monitored by someone who understands what should be going on,and if its not,which bits are wrong and what to do, to correct them.
 
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