Sva Is Doing My Head In!

[jasear]

One of the reasons the altezza failed the sva was on emmisions!

I spoke to the guy who is doing the sva preperation and he told me that giving the car a good run doesnt seem to sort the problem out as the emmissions are still pretty out.

Any idea of how to get the emmisions low enough to pass the sva?

[LennyLexus]

you should have got an IS200 :P

sorry had to stick that in

[TonyGoose]

Not wishing to state the obvious, but ...

Are the cat converters missing, gutted or duff

Oh and could try a new air filter maybe ?

( re-arrange - at straws clutching )

[AltezzaScott]

Not wishing to state the obvious, but ...

Are the cat converters missing, gutted or duff

Oh and could try a new air filter maybe ?

( re-arrange - at straws clutching )

Was gonna suggest checking all of the CATs.... Never had a problem with emmisions...

When it passes.... you`ll be glad you got a TEZZ!! Had to get that in!!

[Leitch]

Did they give you any indication what the problem was?

Eg excess NO or HC? That will give you a clue where to start looking.

[jasear]

Did they give you any indication what the problem was?

Eg excess NO or HC? That will give you a clue where to start looking.

CO emission when rev'd is high at 0.6% and i think the pass is 0.5%!!!!

[Leitch]

Ok, the catlytic converter converts CO to CO2 when it has plenty of oxygen.

High CO occurs when the mixture gets rich. So things to check would be anything that creates an excess fuel mix or leads the ECU to believe the mix is lean and needs to be supplemented with extra fuel:

Others have already said this but look for things that reduce 02 content:

Blocked air filter

or Increase fuel:

Faulty/Blocked injector.

or convince the ECU that the engine is running lean:

Faulty 02 sensor

Keep in mind that the ECU runs in closed or open loop mode. In closed loop mode the engine trys to keep 14.7 lbs of air flowing for every 1 lb of fuel delivered because the catalytic converter works best with this ratio. The ECU checks to see how close to 14.7:1 the ratio is by measuring the oxygen content in the exhaust with the 02 sensor. Closed loop mode is all about minimising emissions and the ECU can compensate for a lot of little variations in operating conditions to achieve minimum emissions. Closed loop is what should be occuring during your SVA test because your engine is not under load (it's cruising at high rpm).

In open loop mode the ECU doesn't care about the 02 content in the emissions and it uses it's internal map of fuel to air ratio's to offer the best drivability/power/acceptable emissions (but not good enough for SVA). There are many instances where the ECU will go to open loop but the two main one are under heavy load when the ECU enters "power enrichment" mode to stop knocking and cold start mode when extra fuel does what a choke did in an older vehicle.

I'm not sure about the UK but usually emissions tests are all about testing the engine during a period when the engine would be in closed loop. I doubt that any engine would have good enough emissions in open loop mode. I think that is why some people are telling you to give it a hard run first. ie the engine is warm so it isn't in cold start mode. The 02 sensor also works better at temperatures above idle so heating it up will help. However, I don't believe either of these are really your issue because your engine will be warm during the test and the 02 sensor has an electric heater that cuts in when the engine idles and it gets too cold.

I suggest that you verify that the temperature sensor is not faulty/unplugged so that the engine stays permanently with the choke out. Verify the 02 sensor is working. Check air filter. Have injectors/fuel system serviced. Last resort because it's a bigger job is to check/change the catalyst. I'm doubtful that your Cat is the problem because your NO emissions would be sky high if it was dead.

If you are looking at a graph of catalyst efficiency vs air/fuel ratio the curve is very steep and a small change in 02 content will give you the change you are looking for. In other words the fault could be pretty minor, just got to find it.

Do you have the HC and NO figures? My guess is that your HC will be a little higher than optimal and your NO will fine if your mixture is a little rich.

Do you have access to a garage with an EG analyser? I think that will be the way to go before you try out for the SVA again.

regards

Terry

[jasear]

Ok, the catlytic converter converts CO to CO2 when it has plenty of oxygen.

High CO occurs when the mixture gets rich. So things to check would be anything that creates an excess fuel mix or leads the ECU to believe the mix is lean and needs to be supplemented with extra fuel:

Others have already said this but look for things that reduce 02 content:

Blocked air filter

or Increase fuel:

Faulty/Blocked injector.

or convince the ECU that the engine is running lean:

Faulty 02 sensor

Keep in mind that the ECU runs in closed or open loop mode. In closed loop mode the engine trys to keep 14.7 lbs of air flowing for every 1 lb of fuel delivered because the catalytic converter works best with this ratio. The ECU checks to see how close to 14.7:1 the ratio is by measuring the oxygen content in the exhaust with the 02 sensor. Closed loop mode is all about minimising emissions and the ECU can compensate for a lot of little variations in operating conditions to achieve minimum emissions. Closed loop is what should be occuring during your SVA test because your engine is not under load (it's cruising at high rpm).

In open loop mode the ECU doesn't care about the 02 content in the emissions and it uses it's internal map of fuel to air ratio's to offer the best drivability/power/acceptable emissions (but not good enough for SVA). There are many instances where the ECU will go to open loop but the two main one are under heavy load when the ECU enters "power enrichment" mode to stop knocking and cold start mode when extra fuel does what a choke did in an older vehicle.

I'm not sure about the UK but usually emissions tests are all about testing the engine during a period when the engine would be in closed loop. I doubt that any engine would have good enough emissions in open loop mode. I think that is why some people are telling you to give it a hard run first. ie the engine is warm so it isn't in cold start mode. The 02 sensor also works better at temperatures above idle so heating it up will help. However, I don't believe either of these are really your issue because your engine will be warm during the test and the 02 sensor has an electric heater that cuts in when the engine idles and it gets too cold.

I suggest that you verify that the temperature sensor is not faulty/unplugged so that the engine stays permanently with the choke out. Verify the 02 sensor is working. Check air filter. Have injectors/fuel system serviced. Last resort because it's a bigger job is to check/change the catalyst. I'm doubtful that your Cat is the problem because your NO emissions would be sky high if it was dead.

If you are looking at a graph of catalyst efficiency vs air/fuel ratio the curve is very steep and a small change in 02 content will give you the change you are looking for. In other words the fault could be pretty minor, just got to find it.

Do you have the HC and NO figures? My guess is that your HC will be a little higher than optimal and your NO will fine if your mixture is a little rich.

Do you have access to a garage with an EG analyser? I think that will be the way to go before you try out for the SVA again.

regards

Terry

Hello terry,

Thanks for your very descriptive reply. You are right that high CO means that the fuel in the fuel air mixture is high or the air is low. thats what causes CO.

However the car was put through a diagnostic test and there was nothing wrong with the ecu unit at all. Everything was working spot on. Lambda reading was also spot on at 1, air fuel mixture was correct as well.

HC emissions were well below the limit of 200ppm they were something like 30 ppm.

With the NO they were spot on too but i dont know the exact readings for them.

Now if everything in the engine and ecu is working fine then it only leaves one thing that could be causing the problem and thats the cat. Do you think that assumption of mine is correct?

In any case can you think of a way around this problem to get the CO emissions down.

thanks,

J.Sear

[ColinBarber]

Not sure what you mean by O2 sensor was spot on at 1. Is that 1volt?

If so then the engine is running very rich. Normal range is .3v to .6v

[jasear]

Not sure what you mean by O2 sensor was spot on at 1. Is that 1volt?

If so then the engine is running very rich. Normal range is .3v to .6v

Not sure myself either but i know that they check ure lambda sensor somehow and the reading must be between 0.7 and 1.03. I think its some kindof a ratio.

[Leitch]

Hmmm.... Thinking aloud...

From memory the catalyst can convert NO emissions fine (>95%) for mixtures that range from fairly rich up to the point that the mixture goes slightly lean then the NO readings go sky high as the mixture leans off and the high temperatures start to cause Nitrogen in the air to react. As your NO is good that is consistent with the mixture being correct or rich. HC tends to follow CO but it's not as sensitive to low oxygen. ie the HC burns better than CO so a slightly rich mix may give you an adequate HC but high CO. Still consistent with a rich mix.

I don't know much about the chemistry of the catalyst except that the catalyst by nature does facilitates the reaction but doesn't get used up by the reaction. It seems to me that a catalyst can only fail if it suffers mechanical (heat) damage that reduces it's surface area or it gets clogged with foreign matter (eg leaded fuel). In either case the Catalyst shouldn't just increase CO emissions, I would expect the HC and NO to be out as well (I just read your other thread and you've already been down that path). You can see I'm not convinced on the Catalyst can't you! Only because it's a pain and $'s if it turns out not to be the case.

I had a look through some Toyota documentation I have and one suggestion from is that a small exhaust leak prior to the cat can mess the ECU's calculations around. I can't quiet visualise the logic but it might be worth checking as this was specifically targeted at hi CO levels.

Something else to try just prior to swapping the cat is to measure the EG emmisions pre and post cat. That should give some indication of how much work the cat is or isn't doing. Always great if you can get another Altezza to compare figures with as well.

Also make sure your mechanic is giving you good advice on what he see's. Emissions numbers in the ppm are pretty fine and out by a little in 02 can mean out by a lot in EG emissions.

When he checks the 02 sensor make sure that it oscillates between rich and lean pretty rapidly (I think Toyota say ~ 8 times a second). The sensor can be "right" but to slow to respond to changes.

Colin has a point about "1" as well. I assumed you meant a balanced (14.7:1) air fuel ratio.

Has the vehicle had a few days driving since it's long rest? I ask because the ECU has both short and long term "trim" values that take time to be learnt.

I'll ponder as to how you can artificially lean it off for the SVA. I don't see that creating an "air leak" will do it as one person says was done with a RAV4. In closed loop mode the ECU should counter that.

Let's see if I can manage to post this just once this time!

cheers

Terry

[ColinBarber]

Yes the O2 sensor should be tested for reaction as they can become slow.

With the sensor oscillating quickly, averaging around .45v a quick squirt of propain will bring the voltage up very quickly and then should go back. Then disconect a vacuum line and the voltage should drop.

[jasear]

Good points!

Ok for starters from the very first day i have always believed that the source of the problem is the fact the car has not been driven for atleast 4 months to my knowledge. Infact it has done roughly 100 miles (according to the guy who took it for an sva) in the last 3 months.

When the guy took the car for an sva he covered roughly 30-40 miles to get to the station then he had to wait for a bit for his turn.

But i have mentioned this to so many different people and none of them really think that thats the problem except for one mechanic i know.

Secondly, i too dont think creating an air leak would work as it would further starve the mixture of air and hence create more CO.

CO is created when there isnt enough oxygen to fully burn the carbon. For e.g CO2 is produced when one carbon atom reacts with 2 oxygen atoms. If there is just 1 oxygen atom available then ull get CO.

As far as the catalyst is concerned it takes no part in the chemical reaction whatsoever. It only speeds up the reaction. I will do some research into how exactly catalytic converters work but from what i know i am sure that they help in burning unburnt gases or partially burnt gases (such as CO, NO, HC) to burn further by supplying more oxygen to them in the presence of a catlyst which should speed up the reaction. So in effect lets say u have CO which enters the catalytic converter where in the presence of more oxygen its converted to CO2.

Suddenly its all becoming clear! Damn! im a chemist i should have known all of this! :)

So basically somewhere in the catalytic converter, maybe due to some blockage, or some other problem the CO's are not being properly converted to CO2.

That could be due to malfunctioning oxygen sensor, lack of oxygen supply due to some bloackage e.t.c. or too much carbon residue building up in the catalytic converter.

I think like you have suggested we should get some readings before the cat to see if the emissions are as expected if so then atleast we know for sure that the problem is the cat! Is it possible to measure the level of emissions before the cat with an altezza? If so then how?

[ColinBarber]

Secondly, i too dont think creating an air leak would work as it would further starve the mixture of air and hence create more CO.

Creating an air leak will increase the amount of air not decrease it. The MAF sensor will not know about the extra air getting in and therefore won't add any extra fuel. If the O2 sensors are working correctly though the ECU will start to add more fuel to compensate.

[jasear]

Secondly, i too dont think creating an air leak would work as it would further starve the mixture of air and hence create more CO.

Creating an air leak will increase the amount of air not decrease it. The MAF sensor will not know about the extra air getting in and therefore won't add any extra fuel. If the O2 sensors are working correctly though the ECU will start to add more fuel to compensate.

So it might just work then!

I think ill give it a try!

[jasear]

but wont the sva guys notice that an air pipe has been disconnected?

[Leitch]

Good to hear you're inspired to keep pushing. A chemist eh! sorry for the chemistry 101 lesson!

Colin- I've never heard of the propane trick before and I'll add it to my repertoire!

The problem with the air leak as Colin says is that the 02 sensor should compensate for it unless you make the leak so large that it is outside the ECU's ability to deal with it. I'm sure other issues will arise at that point.

With regards to the learned trim values in the ECU, I assume that the values are lost (return to default) when the Battery is disconnected for a while. The problems I have heard occuring with this are generally to do with OPEN loop mode when cars experience starting problems after major surgery with Battery disconnected. Those vehicles had their starting problems gradually disappear after a couple of days of use. I'm not sure that this will have much impact on closed loop mode though because its the 02 sensor thats controlling things.

The real issue is why is the ECU not letting the air in by itself when the exhaust is rich? That still points to the 02 sensor.

Let us know how you get on.

[Leitch]

Re: measuring the exhaust gas before the CAT.

Isn't the 02 sensor before the CAT? Sorry if I sound ignorant but I just have an engine (ie I don't have an Altezza to keep it in!) with a partial exhaust. It has the 02 sensor and a short length of exhaust but I didn't get the CAT when I bought the engine. It might be tricky to get a good seal but can you insert the probe into the 02 sensor hole?

[jim]

Could it be a problem with the cat?

I'm trying to remember the chemistry but I am sure there are two different reactions that need to take place. There has to be a reduction going on to convert NOx to N2 then an oxidation to convert the CO to CO2. The oxidation process is also supposed to burn any unburnt hydrocarbons into H2O and CO2.

[jasear]

Could it be a problem with the cat?

I'm trying to remember the chemistry but I am sure there are two different reactions that need to take place. There has to be a reduction going on to convert NOx to N2 then an oxidation to convert the CO to CO2. The oxidation process is also supposed to burn any unburnt hydrocarbons into H2O and CO2.

Ure right, it could be the cat but it also could be a lot of other things! But it sure looks like the cat!

[AMH]

OK - stupid suggestion time - is it worth trying one of those "cure in a bottle" remedies for the cat - I seem to recall seeing bottle of gloop in Big H that claim to rejuvinate cats - might be worth a last ditch go before the expense of a new cat ...

[jasear]

OK - stupid suggestion time - is it worth trying one of those "cure in a bottle" remedies for the cat - I seem to recall seeing bottle of gloop in Big H that claim to rejuvinate cats - might be worth a last ditch go before the expense of a new cat ...

AMH, i have ordered a bottle of cataclean. I thought its worth a try and ill let you guys know if it works or not.

If it doesnt work then my last option is to get the cat replaced.