306 xsi emissions failed

macaroni · Unread post by **macaroni** » 12 Dec 2006, 12:03

Hi,
I have acquired a 306xsi which has failed it's MOT on emissions.

I want to get this going by myself, without resorting to a garage, so I need some advice.

Initially I intend to change the plugs, pour some injector cleaner in and take it for a thrash on a local private road, late at night.

If that doesn't help, what else should I look at? I'm thinking lambda sensor.

Any advice gratefully received.

Cheers,

Antony

pugxpert · Unread post by **pugxpert** » 12 Dec 2006, 20:49

can you post on here the emmision values obtained co,hc,lambda,oxygen etc...??

macaroni · Unread post by **macaroni** » 12 Dec 2006, 21:02

Thanks for the reply. It failed on:

1) Exhaust emissions carbon monoxide content at idle excessive
2) Exhaust emissions carbon monoxide content after 2nd fast idle excessive
3) Exhaust emissions hydrocarbon content after 2nd fast idle excessive
4) Exhaust emission lambda reading after 2nd fast idle outside specified limits.

Fast idle test
Engine speed 2354rpm min max
CO level 12.93% 0.30
HC level 1002ppm 200
Lambda 0.65 0.97 1.03

Second Fast idle test
Engine speed 2089rpm min max
CO level 12.99% 0.30
HC level 893ppm 200
Lambda 0.64 0.97 1.03

Natural idle test
Engine speed 858rpm min max
CO level 5.45% 0.50

Hope this helps.

Antony

Unread post by **CitroJim** » 12 Dec 2006, 22:24

Gosh! It did not just fail, it really failed!

Now I usually get this wrong but it looks like it is running extremely rich to me. Is the Engine Management light on? Some ECUs go rich when they cannot keep things under control to protect the cat.

Things to check, besides the obvious ones like the air filter and normal service items. A good clean out of all the inlet tract, especually the throttle body, and breather hoses always helps.

Coolant Temperature sensor duff. This will make the ECU think the car is always cold and richens the mixture as a result. A common problem on our injection 205s. This'll be my favourite for the cause.

Lambda sensor. Check its connections first before condemming it.

Excess fuel pressure at the injectors due to a duff pressure regulator.

Pipe hanging off the MAP sensor (if it has one) or the pipe perished and leaking. A pals 205 injection had this problem and it stumped a lot of people before I spotted it. It could also be the MAP sensor itself.

Air leaks. These usually cause a weak mixture but sometimes they can fool the metering system into believing there is more air going into the engine than there actually is, resulting in a rich mixture.

Finally, the Inlet Air Temperature Sensor.

Hope that helps a bit...

macaroni · Unread post by **macaroni** » 12 Dec 2006, 23:14

Wow, thanks for that reply!

I'll go through that checklist as soon as I have the car, which should be tomorrow.

macaroni · Unread post by **macaroni** » 13 Dec 2006, 20:16

Well I got the car and it seems pretty good. After putting a new battery on it started on the button and settled to a very sweet idle.
All the toys work, electric windows, sunroof, mirrors, central locking.
The heater controls were a bit stiff and I think I broke the direction control - oops!
It is very dirty and should be worth doing up.
One thing is, it doesn't have alloys! Didn't all xsis have alloys?

First job is to check the plugs etc add some injector cleaner and spray the intake tract liberally with carb cleaner and take her for a good thrash. Then I will change the oil and filter and get an emissions check before tackling anything else.

pugxpert · Unread post by **pugxpert** » 13 Dec 2006, 20:49

does the engine run ok because that looks well rich to me especially hyrdocarbons!! is it misfiring or low on compression??

macaroni · Unread post by **macaroni** » 13 Dec 2006, 21:24

I take your point, but it seemed to run very sweetly. I only ran it for about 10 minutes on the drive and then drove it into my garage, but it was lovely. It held a very solid 800rpm idle and revved to about 4500rpm very cleanly.

I guess if the car runs nicely, but the emissions are high then the problem may lie with the car convertor?

pugxpert · Unread post by **pugxpert** » 14 Dec 2006, 20:23

if the cat has gone the lambda value will remain at 1 and you would get about .5% of co and a sniff of oxygen and a reduced co2 value but your lambda value is lower than 1 which means its rich poss oxygen sensor or something is telling ecu incorrect info such as map sensor or coolant temp as previously advised,fuel pressure is a first as if its too high say 4/5 bar then almost double the fuel going in.. also take injectors out and crank with them disconnected (electrically) and check for leaking

macaroni · Unread post by **macaroni** » 14 Dec 2006, 21:59

OK, thanks for that advice. You could be right as I have just changed the plugs and the old ones were black as soot.

I stuck some injector cleaner in and will give it a thrash tomorrow. Then I will check your suggestions:

- O2 sensor
- map sensor
- coolant temp sensor

If you can tell me where these things are, it would be a big help. I'm guessing the O2 sensor is by the inlet manifold, the map sensor by the TB and the coolant temp sensor screwed into the thermostat housing?

When the ignition is turned on, the fuel pump does sounds quite loud, but it does switch off after a 2nd or 2, until I crank it.

Thanks again for the advice.

Antony

rossd · Unread post by **rossd** » 15 Dec 2006, 08:11

The 02 sensor will be in the exhaust downpipe before the Cat, usually got 2 or 4 wires coming off it.

macaroni · Unread post by **macaroni** » 15 Dec 2006, 11:33

'Scuse my ignorance, but is an O2 sensor the same as a Lambda sensor?

Unread post by **CitroJim** » 15 Dec 2006, 12:05

Yes, it is. The terms are interchangable.

O2 sensing is what it does, reads the level of oxygen in the exhaust gas. Too much means not all of the available oxygen taken in has been used in combustion.

Lambda is the mixture ratio effectively. Lambda = 1 means stochometric (sp?) or 14.7:1. A lambda of less then one means a rich mixture and a Lambda above 1 means a weak mixture with excess oxygen being present.

Unread post by **CitroJim** » 15 Dec 2006, 12:15

To expand a bit, at Stochiometric (14.1) all the oxygen taken in will be used to completely combust the fuel and the exhaust gas will be CO2 and a bit of NOx (Nitrogen Oxides) and H2O (Water vapour).

Under rich conditions there is not enough oxygen present for full combustion and the exhaust will have a high level of CO (Carbon Monoxide) as well as NOx and CO2.

Under weak conditions, there is not enough fuel present to completely consume all the available O2 (Oxygen) so excess O2 will appear in the exhaust gasses.

Hope that makes a bit of sense.

macaroni · Unread post by **macaroni** » 15 Dec 2006, 12:28

Yes thanks for that, it's somewhat clearer now.

In answer to a question above, the engine management light is on.

So if it's running rich, Am I better off looking for the cause of the condition like the coolant temp sensor, fuel pressure, injectors etc before looking at the lambda sensor?