MOT today and Emissions failure :(

[RichG60 0]

Hi guys had my MOT today and failed badly on emissions. As far as I'm aware all sensors are new about a year ago by the previous owner. New co pot and Lambda sensor.

 

The car is running an SNS 5.5 chip.

 

The test results are as follows :-

 

co level 8.15% vol

hc level 292 ppm

co2 level 9.5 % vol

 

what should I check first?

 

I guess I should be looking at adjusting the co pot but what reading should I be looking for with this chip?

 

What is the exact procedure? Take the reading when at normal running temperature across contacts 1-3?

 

Cheers

 

Rich

[DanVW 0]

Have you had the co set with a widband? iirc the CO pot should be set to run at 14.5-15 AFR at idel to pass emmitions and for economy, if not you are probably looking at a new Cat

[RichG60 0]

Thanks for the response, the car doesn't have a cat, doesn't need one as pre Aug 92. I haven't set the co pot with a wideband.

[mikkijayne 0]

Wow with numbers like that the exhaust probably smells awful doesn't it? Is it blowing any soot out of the tailpipe? Can you tune it by smell?

 

Do you have the stock chip? I've seen bad tunes on G40s fail emissions no matter what, so it might be worth sticking the stock one back in just for the MoT.

[Supercharged 2]

I'd suspect a setup / sensor issue as the SNS chips run fairly clean (providing it's for the right size pulley etc!)

 

Was the Lambda genuine Bosch? - The universal ones seem to last 5 minutes.

[RichG60 0]

As far as I'm aware the car was set-up by g-werks when the previous owner had it. The car is running a 68mm pulley with a stage 4 charger. I did a full service on her last weekend. Yes the car smells a bit rich but that Is from the deleted boost return up front. The car runs beautifully and mpg is very good. No unburnt fuel coming out of the exhaust and it's not blacked with fuel. The old spark plugs were very healthy with no signs of over fueling.

 

As for the lambda I will get under the car tonight and check. Do you think it could be this that's shot?

 

Thanks

 

Rich

[RichG60 0]

Looking at the receipts G-werks replaced the co pot last year on its MOT, I can't find any records of a new lambda though. Which one would I be looking at getting? I notice there are a few Bosch Lambda's on Euro car parts for the G60.

[RichG60 0]

Is this the one to get?

http://cgi.ebay.co.uk/Bosch-Front-Lambd ... 286.c0.m14

[mikkijayne 0]

Yes the car smells a bit rich but that Is from the deleted boost return up front.

 

Why would that make it run rich? :confused4:

[dirtytorque 0]

/\/\/\

 

it wouldn't..

[RichG60 0]

Yes the car smells a bit rich but that Is from the deleted boost return up front.

 

Why would that make it run rich? :confused4:

 

I didn't say that it made it run rich I said it smells rich because the boost return is vented to atmosphere.

[RichG60 0]

This is my lambda sensor :-

 

 

Best picture i could take given the position of it. Does it look like a Bosch one?

 

If the lambda is faulty wouldn't my idle be erratic?

[coolrado 0]

the lambda sensor could be fine, but try checking the wiring to the connector on the lambda side and the loom side, it's quite common for the wires to corrode and snap.

[RichG60 0]

The full test results are :-

 

CO 8.15 % vol

HC 292ppm

CO2 9.50%

O2 0.72 % vol

LAMBDA 0.80

 

Do the other figures help in diagnosing my problem?

[RichG60 0]

Anyone?? :(

 

This is the first car I've had that has failed an mot, I have a few other things to do but the emission thing is the biggest thing and I don't have long to go so any help would be much appreciated :).

[mikkijayne 0]

 

I didn't say that it made it run rich I said it smells rich because the boost return is vented to atmosphere.

 

Ah ok :) What about the exhaust on it's own? If you take a good whiff of that close up I bet you can smell it's rich at 0.8 Lambda.

 

I would mark where the CO pot is set to and try adjusting it so it smells right. If you have a friendly MoT tester he would probably do this for you on the sniffer before re-testing it for a small fee.

 

Also try holding a white rad over the tailpipe for a minute or two while it's idling. At 0.8 you will probably get a bit of soot on it. Tweak until the exhaust is clean.

 

In case it helps, the G60 only uses the Lambda for closed-loop at idle, reverting to it's maps when running (so a broken one won't affect normal running or fuel consumption). If you unplug the Lambda it will run open-loop just using the basic map and CO pot settings. If you have a faulty sensor that is feeding the ECU bad data then unplugging it should improve the emissions, so thats worth a try before you buy a new one. Unplug it and see if the smell changes. If it leans out you have a bad sensor.

 

I believe the CO pot is also only used to set the closed-loop idle mixture, but not 100% on that if anyone else cares to chime in?

 

That does look like a stock Bosch sensor in the pic.

[RichG60 0]

Thanks for that, I marked the co pot with its current position and tried to adjust it. Turning it a couple times made no difference to the car at all e.g. it kept idling and running as it has been.

 

I unpluged the co pot from the boost pipe and blew across it and again no change to the car.

 

Does this suggest its dead?

[RichG60 0]

I tested pins 1 and 3 of the co pot and it is set to 700 ohms is this too high?

[RichG60 0]

I guess with the co pot set as it is slighty on the side of lean this isn't at fault. I will try disconnecting the lambda to see if this makes any difference. Also I read that the blue coolant sensor could be causing a problem. Is this worth changing?

[RichG60 0]

Anybody??

[dirtytorque 0]

I guess with the co pot set as it is slighty on the side of lean this isn't at fault. I will try disconnecting the lambda to see if this makes any difference. Also I read that the blue coolant sensor could be causing a problem. Is this worth changing?

 

 

worth a shot,if the engine isn't coming out of warm up enrichment because the sensor is reading too cold then that would cause the car to run rich during the test.

[RichG60 0]

Ok cheers, does the blue top coolant temp sensor provide the reading to the ecu & the black top one do the temp gauge.

 

Only reason I ask is because the temp gauge is reading correctly.

[Walesy 0]

I tested pins 1 and 3 of the co pot and it is set to 700 ohms is this too high?

 

 

Should be around 500ohms as far as I can remember mate

[mikkijayne 0]

Ok cheers, does the blue top coolant temp sensor provide the reading to the ecu & the black top one do the temp gauge.

 

Only reason I ask is because the temp gauge is reading correctly.

 

Yes thats right.

[RichG60 0]

Today I have been pretty busy on the rado,

 

Changed the n/s brake line to master cylinder

n/s rear calliper flexi hose

n/s rear brake line to ldv

o/s steering rack boot & track rod end ball joint

Adjusted the parking brake

Adjusted the headlight height

But finally changed the bts (Blue temperature sender)

 

Problem is the revs rise slightly from 750/800 – 900rpm when the BTS is disconnected at normal running temperature. Is this something to worry about, I read on the forum that they are supposed to drop.

 

I have no idea if the emissions have improved though, put some kitchen roll against the tail pipe when the car was up to temperature and there was no soot (excess fuel) on it.