Should be a four wire with heater.
Cheers
PD
Cheers
PD
General mot emissions
- Thread starter irabbit
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General
mot emissions
I am thinking that if the heater element is going down or just intermittant, maybe its not getting hot enough to go into closed loop and giving conflicting results. It is weird that the system is not protesting with the sensor unpluged.
I dont think the O2 sensor is cheep to replace, if it were me I would try the temp sensor first for around a tener.
Did you manage to get any results with your testing?
I dont think the O2 sensor is cheep to replace, if it were me I would try the temp sensor first for around a tener.
Did you manage to get any results with your testing?
Just take your time and make sure you have good lighting and you will be ok. Although everyone on this site only wants to help each other its hard when you are not there to see it for yourself, and sometimes its more than one thing or something different alltogether; thats why its good to come back and tell us about how the fix was acheived so we can all learn.
i will post results of checks and if still no answer i am going to take car to another garage to get to bottom of problem. apart from emissions everything else ok apart from car idles at about 2000 revs when started for about 5 minutes before settling to about 1000 revs ?
Now you mention the rpm's I am more inclined to suspect the temp sensor (also known as the coolant temprature sensor). If the ECU thinks the engine is cold it will enrich with extra fuel, as it will not register the drop in resistance as the engine warms up.
Just like your brain will instruct your hands to move and your legs to start walking, so will the vehicle sensors instruct the ECU to carry out their tasks. i.e operate actuators and deliver fuel. The temp sensor is critical to the proper operation of the engine.
just fitted new temp sensor which cost £8.00 from fiat.
this brought idle down to about 900 rpm.
don't know about emissions though as we did a compression test and found readings of 14 - 12 - 5 - 14.
this makes me think there is a big problem with engine even though it runs well.
any ideas anyone before i spend more money on emissions tests ?
this brought idle down to about 900 rpm.
don't know about emissions though as we did a compression test and found readings of 14 - 12 - 5 - 14.
this makes me think there is a big problem with engine even though it runs well.
any ideas anyone before i spend more money on emissions tests ?
That compression needs looking into, could be lots of things, from worn rings valves or head gasket. Now the temp sensor is working the engine won't be over fueling and if it were me I would give it another bash, you have already saved yourself money by carrying out the work yourself, how much do you think a garage would charge you to diagnose and put that sensor in. Your CO2 was not that much over limits, once you have got the MOT you have time to sort out other problems.
Good luck.
Good luck.
cueboydave
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- Nov 20, 2008
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I'd go for new lambda sensor, most common culprit for high emissions.
I may be inclined to agree about the lambda sensor if the lambda window of 0.97-1.03, were out of limits, however this particular vehicle was within limits. When the lambda sensor is working correctly the quantity of oxygen within the exhaust is being accurately measured by the lambda sensor to acheive the said limits. After some further thought, the fact stop smoke soloution was added to the vehicle before the second test may have obscured the readings, so the dury is still out on the lambda.
I would say the poor old lambda is a much overlooked sensor, it sits there doing its thing whilst exposed to the elements and has to endure freezing tempratures that can rise to 600deg, in fact the sensor won't start working until around 400deg. Even when your caterlistic converter is going a bit wobbly through old age the good old lambda helps compensate to keep everything within limits.
I would say the poor old lambda is a much overlooked sensor, it sits there doing its thing whilst exposed to the elements and has to endure freezing tempratures that can rise to 600deg, in fact the sensor won't start working until around 400deg. Even when your caterlistic converter is going a bit wobbly through old age the good old lambda helps compensate to keep everything within limits.
just an update on car.
it seems that head gasket or a valve or both have gone.
head coming off this week and i will post findings on here.
thanks for all suggestions.
jon.
p.s. anyone know best place for recon head etc ?
it seems that head gasket or a valve or both have gone.
head coming off this week and i will post findings on here.
thanks for all suggestions.
jon.
p.s. anyone know best place for recon head etc ?
update as promised.
i have now had head gasket done along with timing belt.
once again failed on emissions.
after checking "everything" the mechanic removed cat and found it destroyed.
this has been replaced and emissions now almost 0.
this well learned lesson has now set me back £1000.00 for a car worth half that. however it has a new head and 12 months mot.
just shows it sometimes is the most obvious things that are ignored.
jon.
i have now had head gasket done along with timing belt.
once again failed on emissions.
after checking "everything" the mechanic removed cat and found it destroyed.
this has been replaced and emissions now almost 0.
this well learned lesson has now set me back £1000.00 for a car worth half that. however it has a new head and 12 months mot.
just shows it sometimes is the most obvious things that are ignored.
jon.
You have certainly had a steep learning curve, however your diagnostics had lead you to to take correct action regarding the head which would have proberly let you down at some stage. The cat must have been damaged in some way, which was likely a symptom of the other problems you or the previous owner were experiencing, I did not mention the cat may have broken down in earlier posts because you did not mention a bad smell likeing to rotten eggs (Sulphur) when starting or accelerating which is a common indicator of a cat that has broken down.
There are things that can damage a cat -
1.Missfire or over use of bump starting, leading to over heat causing burning within the cat.
2.Using the wrong fuel. i.e. leaded petrol, or some fuel additives or poisoning from silicon.
3.Burning oil to the extent of blue smoke being produced.
4.High carbon build up.
5.Being struck against whilst working on the vehicle.
A well maintained ignition system and regular servicing should help ensure you cat will acheive 50,000-100,000 miles. The Lambda sensor will help correct some damage, and some vehicles now have two sensors to make a cat even more stable.
As you learn, become more proficient and take on the work yourself, you will save a huge amount of money. Remember hind sight can make us all wonderful mechanics, unfortunatly you just can't buy it off the shelf. Thanks for getting back to us.
There are things that can damage a cat -
1.Missfire or over use of bump starting, leading to over heat causing burning within the cat.
2.Using the wrong fuel. i.e. leaded petrol, or some fuel additives or poisoning from silicon.
3.Burning oil to the extent of blue smoke being produced.
4.High carbon build up.
5.Being struck against whilst working on the vehicle.
A well maintained ignition system and regular servicing should help ensure you cat will acheive 50,000-100,000 miles. The Lambda sensor will help correct some damage, and some vehicles now have two sensors to make a cat even more stable.
As you learn, become more proficient and take on the work yourself, you will save a huge amount of money. Remember hind sight can make us all wonderful mechanics, unfortunatly you just can't buy it off the shelf. Thanks for getting back to us.
Last edited:
Road Damage
This is external damage caused to the catalytic converter by hitting solid objects in the road. i.e., speed bumps, large rocks etc.
Plugged Or Contaminated.
Plugged or contaminated catalytic converters are caused by using the wrong sort of fuel in your car. Using leaded or lead replacement fuel will plug up the monolith and cause it to stop working. A similar thing will happen if fuel additives are used that are not suitable for use with a catalytic converter.
Oil Fouled
This is caused by oil getting into the exhaust system and contaminating the catalytic converter. The most likely cause is a leaking gasket.
Melted/Broken Substrate
A monolith is usually broken when it is impacted by an object or when it suffers a sudden change in temperature. If the cat suffers road damage (See section on “Road Damage”) the monolith inside can be cracked due to it being crushed by the movement of the steel can.
The use of exhaust paste before the cat can also cause the monolith to break. When the exhaust paste has hardened small pellets can break away and shoot into the cat. The monolith will gradually be destroyed by these pellets and break down. The cat can also be destroyed by excessive engine vibration.
A rapid change of temperature can also break the monolith. (See number 7 in “Caring for your Catalytic Converter”)
The monolith can be melted when unburned fuel is injected into the cat. This can be caused by the car being tow or bump started, or if the car’s engine requires several turns before firing. More information on the causes of melting monoliths can be found in the section on “Overheating”.
Overheating
There are many problems that can cause a cat to overheat or fail. The most common cause is unburned fuel entering the cat. Also faulty spark plugs and leads will cause the engine to misfire and ruin the converter. The cat will also be ruined if the distributor timing is out.
Oxygen Sensor
An oxygen sensor collects and sends information to the Electronic Control Unit. This is used to control the air/fuel mix . If the oxygen sensor is faulty, or it has been contaminated with silicone from anti-freeze or sealant, the air/fuel mixture will not be corrected and excess fuel will enter the cat, causing it to overheat.
Fuel Injection Systems
If a fuel injector is leaking internally or dribbling fuel into the engine the converter may be damaged. The excess fuel will enter the exhaust system and cause the cat to overheat. Due to the varying fuel injector systems the proper manual should always be consulted when trying to diagnose a problem.
Map Sensors
Map Sensors tell the Electronic Control Unit the load on the engine and the amount of air entering it. If this sensor fails it causes a rich condition in the engine which can overheat the cat and cause it to fail.
Carburettor Systems
A worn or defective carburettor can cause a cat to overheat. Problems such as improper float or air/fuel mix adjustments and worn metering rods can damage the cat. The choke system also needs to be operating properly so the right level of fuel enters the system. If too much fuel enters the system the cat will overheat and eventually fail.
Canister Purge Valve Control
This vacuum operated valve vents fuel vapour from the carburettor bowl to the charcoal canister. If the vacuum is breached the charcoal canister will flood, causing the air/fuel mixture to become very rich. This will cause the converter to overheat and eventually fail.
I'm suprised it manages to last?
This is external damage caused to the catalytic converter by hitting solid objects in the road. i.e., speed bumps, large rocks etc.
Plugged Or Contaminated.
Plugged or contaminated catalytic converters are caused by using the wrong sort of fuel in your car. Using leaded or lead replacement fuel will plug up the monolith and cause it to stop working. A similar thing will happen if fuel additives are used that are not suitable for use with a catalytic converter.
Oil Fouled
This is caused by oil getting into the exhaust system and contaminating the catalytic converter. The most likely cause is a leaking gasket.
Melted/Broken Substrate
A monolith is usually broken when it is impacted by an object or when it suffers a sudden change in temperature. If the cat suffers road damage (See section on “Road Damage”) the monolith inside can be cracked due to it being crushed by the movement of the steel can.
The use of exhaust paste before the cat can also cause the monolith to break. When the exhaust paste has hardened small pellets can break away and shoot into the cat. The monolith will gradually be destroyed by these pellets and break down. The cat can also be destroyed by excessive engine vibration.
A rapid change of temperature can also break the monolith. (See number 7 in “Caring for your Catalytic Converter”)
The monolith can be melted when unburned fuel is injected into the cat. This can be caused by the car being tow or bump started, or if the car’s engine requires several turns before firing. More information on the causes of melting monoliths can be found in the section on “Overheating”.
Overheating
There are many problems that can cause a cat to overheat or fail. The most common cause is unburned fuel entering the cat. Also faulty spark plugs and leads will cause the engine to misfire and ruin the converter. The cat will also be ruined if the distributor timing is out.
Oxygen Sensor
An oxygen sensor collects and sends information to the Electronic Control Unit. This is used to control the air/fuel mix . If the oxygen sensor is faulty, or it has been contaminated with silicone from anti-freeze or sealant, the air/fuel mixture will not be corrected and excess fuel will enter the cat, causing it to overheat.
Fuel Injection Systems
If a fuel injector is leaking internally or dribbling fuel into the engine the converter may be damaged. The excess fuel will enter the exhaust system and cause the cat to overheat. Due to the varying fuel injector systems the proper manual should always be consulted when trying to diagnose a problem.
Map Sensors
Map Sensors tell the Electronic Control Unit the load on the engine and the amount of air entering it. If this sensor fails it causes a rich condition in the engine which can overheat the cat and cause it to fail.
Carburettor Systems
A worn or defective carburettor can cause a cat to overheat. Problems such as improper float or air/fuel mix adjustments and worn metering rods can damage the cat. The choke system also needs to be operating properly so the right level of fuel enters the system. If too much fuel enters the system the cat will overheat and eventually fail.
Canister Purge Valve Control
This vacuum operated valve vents fuel vapour from the carburettor bowl to the charcoal canister. If the vacuum is breached the charcoal canister will flood, causing the air/fuel mixture to become very rich. This will cause the converter to overheat and eventually fail.
I'm suprised it manages to last?
