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[vauxnut]

have just had the car in for mot and it failed for being to lean on one part off emmisions.please can any one help.                                       on a ligther note  you would think to lean means less emmisions.is this not what we have been brainwashed into thinking is better for all.  hay ho.

[Kevin Wood]

on a ligther note  you would think to lean means less emmisions.is this not what we have been brainwashed into thinking is better for all.  hay ho.

You'd be surprised how much fuel modern cars waste in order to meet emissions regulations!

Do you have the details from the print-out from the emissions test? Would be interesting to have a look.

Kevin

[vauxnut]

fast idle test  eng sp  2750-3250rpm                                                  co max 0.30%  reading 0.00%      pass                                            hc max200ppm  reading 22 ppm     pass                                            lambda 0.97-1.03 reading 1.30 fail                                                    second fast idle test  eng speed 2750-3250 rpm                                 co max 0.30%  reading 0.00%      pass                                             hc max 200ppm  reading  4ppm    pass                                             lambda 0.97-1.03  reading 1.28    fail                                                natural idle test 755-1075 rpm   reading 766rpm                                co max 0.50%  reading0.00%  pass                                                  what do think

[Abiton]

Exhaust leak after cat, drawing in air to give false lambda reading?

Can't really be running 1.3 lambda surely...

[Kevin Wood]

Exhaust leak after cat, drawing in air to give false lambda reading?

Can't really be running 1.3 lambda surely...

I tend to agree. That's an AFR of 19:1. I doubt the rest of the tests would pass if the mixture is that far out. Not sure now clever MOT emissions devices are at discriminating against air leaking in?

I'm sure the ECU would be complaining if the Lambda sensor had sent it that lean.

Kevin

[vauxnut]

thanks for your thoughts.i have the print out  and have checked it to the details i posted earier and they are as printout.the guy who done the mot thinks the problem could be the age off the exhaust ,and have lots of very small pin holes(the exhaust has been repaired in the past,dose not appear to be ready to fall off) the mot tester found it strange that the lambda was approx 1.3 at engine speeds from app2-4000 rpm,closing comment from mot tester was poss air leak on inlet side but had not seen this on the 4 pot eng.

[Kevin Wood]

Does the engine run OK? Any signs of a misfire, hesitation or backfiring?

If not, I'd suggest it's the exhaust. An engine won't run happily at a lambda of 1.3.

Kevin

[ngrainqey]

in my experience of broken lambdas it runs underpowered!
and engine check light came on so doubt its the actual lambda sensor  

[markey mark]

sounds like it needs a damn good thrashing on a private road  

[vauxnut]

hi all    did have misfire had code po270 low voltage to no4 ing sorted by cleaning connectors,that seems ok now,have in last 4-6 wks changed plugs/checked for oil in plug well/fitted new erg valve,had a lot of what seemed to be instant gasket on board.

[Kevin Wood]

EGR valve could be confusing things if it's leaking. Someone has obviously been dabbling there before. Might be worth trying blanking it off.

Kevin