Avensis 1.8Vvti Stays In Open Loop At 2500Rpm (Fails Emissions)

[anthony_linac]

Hi,

I have an avensis 1.8 vvti (year 2000). It failed the fast idle test (approx 2500rpm) on the MOT having high CO content (2-3%) etc. I have taken it to a garage and had it on the diagnostic kit. This showed lambda sensors switching quite happily at idle, and the ECM in closed loop. As soon as the revs are applied, the ECM switches into open loop, the lambda sensors stop switching, and the emissions go through the roof. Even if the engine is held at 2500rpm for several minutes the ECM remains in open loop. When the throttle is removed, and the engine goes back into idle, the ECM switches back to closed loop, and emissions come back down. As long as this keeps happening, this car will never pass MOT, which is ridiculous because its only done 88,000 miles and is a great car to drive. Anyone got an idea whats goin on?

Cheers

Ant

[Roker]

If the Lamda sensor stops switch, why do you not suspect this? has it ever been changed? it is only gauranteed for about 55,000 mile.

[anthony_linac]

If the Lamda sensor stops switch, why do you not suspect this? has it ever been changed? it is only gauranteed for about 55,000 mile.

I tried swapping the lambda sensors out just as a precaution, but it made no difference. The Lambda sensors are passive, and merely measure the Oxygen content of the exhaust gas. It is perhaps misleading to think the lambda sensor itself is switching. It is actually the ECM which causes the 'switching' when it goes into closed loop mode. In this mode the ECM looks at the signals from the lambda and decideds if the mixture is too rich/weak, then corrects accordingly. Hence, in closed loop the signal goes rich-weak-rich-weak....as the ECM is constantly trying to correct it. When the engine is idling, the diagnostic kit showed the following:

Engine in CLOSED LOOP

Lambda 'switching' between 0.8-0.2V

However, as soon revs are applied, the ECM goes in to open loop which means it is no longer trying to control the mixture, hence the lambda sensors are just measuring the oxygen content of the exhaust gas. So, the sensors are reading correctly, they say the mixture is rich, its just the ECM ignores it. The ECM is supposed to reamin in closed loop under these situations.

Cheers

Ant

[Q.S.]

If the Lamda sensor stops switch, why do you not suspect this? has it ever been changed? it is only gauranteed for about 55,000 mile.

I tried swapping the lambda sensors out just as a precaution, but it made no difference. The Lambda sensors are passive, and merely measure the Oxygen content of the exhaust gas. It is perhaps misleading to think the lambda sensor itself is switching. It is actually the ECM which causes the 'switching' when it goes into closed loop mode. In this mode the ECM looks at the signals from the lambda and decideds if the mixture is too rich/weak, then corrects accordingly. Hence, in closed loop the signal goes rich-weak-rich-weak....as the ECM is constantly trying to correct it. When the engine is idling, the diagnostic kit showed the following:

Engine in CLOSED LOOP

Lambda 'switching' between 0.8-0.2V

However, as soon revs are applied, the ECM goes in to open loop which means it is no longer trying to control the mixture, hence the lambda sensors are just measuring the oxygen content of the exhaust gas. So, the sensors are reading correctly, they say the mixture is rich, its just the ECM ignores it. The ECM is supposed to reamin in closed loop under these situations.

Cheers

Ant

Is engine reaching normal running temp ok (and staying there when revs are up)? Is temperature sensor ok?

[anthony_linac]

If the Lamda sensor stops switch, why do you not suspect this? has it ever been changed? it is only gauranteed for about 55,000 mile.

I tried swapping the lambda sensors out just as a precaution, but it made no difference. The Lambda sensors are passive, and merely measure the Oxygen content of the exhaust gas. It is perhaps misleading to think the lambda sensor itself is switching. It is actually the ECM which causes the 'switching' when it goes into closed loop mode. In this mode the ECM looks at the signals from the lambda and decideds if the mixture is too rich/weak, then corrects accordingly. Hence, in closed loop the signal goes rich-weak-rich-weak....as the ECM is constantly trying to correct it. When the engine is idling, the diagnostic kit showed the following:

Engine in CLOSED LOOP

Lambda 'switching' between 0.8-0.2V

However, as soon revs are applied, the ECM goes in to open loop which means it is no longer trying to control the mixture, hence the lambda sensors are just measuring the oxygen content of the exhaust gas. So, the sensors are reading correctly, they say the mixture is rich, its just the ECM ignores it. The ECM is supposed to reamin in closed loop under these situations.

Cheers

Ant

Is engine reaching normal running temp ok (and staying there when revs are up)? Is temperature sensor ok?

Yes, the engine is reaching normal running temp. In fact the temperature sensor was replaced as a precaution

[anthony_linac]

I have also tried changing the lambda sensors but to no avail. Only other thing I can think of is throttle position sensor, but I have checked this with a meter, and also checked it moves smoothly using a diagnostic analyser

[anthony_sorearse]

I have also tried changing the lambda sensors but to no avail. Only other thing I can think of is throttle position sensor, but I have checked this with a meter, and also checked it moves smoothly using a diagnostic analyser

The ECU is likely at fault. But if you change this you will also need to reprogram your keys for the central locking. Some people have managed to successfully reprogram their keys by simply shoving it up their *****. To see if you possess this skill just whack the key up your fat tight little ***** and squeeze hard: if your car opens bobs your uncle

If that fails link the diagnostic analyzer up to your nipples to ensure you are lactating: this helps the programming process.

[fixitphil]

Hi Ant,

Saw your problem! Did you ever get it sorted? I have just posted a possibly similar fault.

Best regards

FixitPhil (if I can find out what's wrong)

[Konrad C]

Phil,

I answered your post. Anthony found out he had a problem via the MOT emission test. Your issue is due to the car lacking power.

Have you had the emissions for your car checked - is your catalytic converter blocked causing the lack of power.

The other thing is that the engines are different, but both mentioned 'open loop'.

Anthony,

The same question - are your catalytic converters damaged?

Both of you looked at the sensors, but the cats may not be working properly.