Failing emissions Test even with a replaced Cat? Diagnose?

[Mr2Owner]

High lambda reading means that the gas mixture is lean. 1.19 would be *very* lean. To me, this suggests you've got a leak somewhere - extra air in the exhaust system is causing the gas mixture in the exhaust to read lean. This does *not* mean the engine itself is running lean. If the leak is upstream of the lambda sensor, then this will throw off the ECU's lambda reading, and therefore throw off the fuelling. So, this could be linked to your high CO problem.

Find the leak!

Thanks for the reply. I had the car up on a lift today with a mechanic and we didn't see any leaks. I've had the exhaust off at the Cat, backbox and up at the turbo and used all new gaskets except for the metal one at the turbo to cat which as it was in good condition. After checking the exhaust today I'm pretty sure there isn't a leak.

Could an aftermarket K+N air cone filter or issues with leaking air hoses as opposed to exhaust leaks cause a running lean scenario too?

I'm going to change the Lambda sensor with a Denso one, where ar you folk buying the Denso ones as the motor factors couldn't get me a Denso one? Can I get a Denso somewhere other than Toyota?

I'm starting to lose interest in the car now, every emissions test done on it seems to give completely different readings.

[Nic]

Do a vehicle search here and find the Denso part number you need, then do a Google search of the part number to find retailers.

http://www.denso-am.co.uk/e-catalogue/

[Mr2Owner]

Do a vehicle search here and find the Denso part number you need, then do a Google search of the part number to find retailers.

http://www.denso-am.co.uk/e-catalogue/

Cheers for that link, it appears i need the Denso part number DOX-0215 for the 3S-Gte engine. Ill search for one online, thanks.

I searched and found the below, apparently the same sensor in the ST185 celica GT4 model. I'll buy this one.
http://www.sparkplugs.co.uk/denso-oxyge ... r-dox-0215

[Mr2Owner]

I'm in the process of checking the Lambda sensor as I've finally bought an Analogue multimeter with a needle. I'm trying to test it via the instructions in the link below. I've a quick question, do I set the multimeter at DCV50 like in the pic below where I put the red arrow? Is that where I should have the dial set to?



http://mr2.ie/mr2/bgb/mk2/mechanical/34.html

[Mr2Owner]

When I put the Analogue meter at DCV50 setting with the Dial and put the probes on TE1 and E1 to count the needle fluctuations, the needle doesn't move at all.

Also, when I do the Voltage check of the Lambda sensor using a digital multimeter by putting the +probe on VF1 and -probe on E1 and holding the revs at 2500 rpm I get a reading of 3volts and that drops to 0.1volts when I let the revs off to just idle.
The guide says to replace the Oxygen sensor if More than 0volts.

Does this suggest the Lambda sensor is faulty?
And am I putting the Analogue on the correct setting to perform the needle fluctuation test can someone confirm?

[Mr2Owner]

Just bumping this to see if anyone can give me some more advice on the above questions.

Just to add, I done the resistance test of the O2 sensor as described in the Toyota manual link on the previous page where it says to test resistance between +B and HT. I think these are the 2 heater wires which are the 2 black wires of the sensor. Can anyone confirm it ts the 2 heater wires I should be testing resistance between?

The resistance reading should be between 5.1 and 6.3 according to the Toyota manual. The readings i got using resistance was 1.0
When I tested for continuity between the 2 heater wires I got 05.5

Does all this suggest the O2 sensor is faulty?

[MartinF]

Put it on 10v, that should be fine.

Also I think the positive probe should be on VF1, like when you checked with your digital meter.

[Mr2Owner]

Put it on 10v, that should be fine.

Also I think the positive probe should be on VF1, like when you checked with your digital meter.

I'll try it again with the it set to 10v and see if the needle fluctuates then. Thanks for the suggestion

Why do you think it should be on VF1, the manual states Vf1 and E1 for the voltage check which I used the Digital meter on. But for the needle fluctuations test it states to use TE1 and E1. Do you think the TE1 is a misprint and they meant to say VF1?

[Mr2Owner]

Think I might have read the the procedure wrong. Do they mean to bridge the terminals TE1 + E1 with a paper clip and then whilst they are still bridged then put the voltmeter on terminals VF1 and E1.

I wasn't using the voltmeter whilst TE1 and E1 were bridged at the same time. Maybe I'll try that.

[Mr2Owner]

Ok, the car didn't like it when I bridged TE1 + E1 with the car running, as soon as I bridged them terminals, the engine revs raised and the engine management light was on.

So I just checked the voltage from VF1 and E1 again and its at 3volts approx at 2500rpm then drops to 0.10 when ideling.

I believe a Lambda senso should only go to a max voltage of 0.9v so maybe its faulty.

I don't think I'm going to be able to test the sensor regards counting the needle fluctuations as the procedure seems to be stated wrongly in the Toyota manual.

Has anyone here managed to test the sensor in this way?

[abovetherim]

Ok, the car didn't like it when I bridged TE1 + E1 with the car running, as soon as I bridged them terminals, the engine revs raised and the engine management light was on.

So I just checked the voltage from VF1 and E1 again and its at 3volts approx at 2500rpm then drops to 0.10 when ideling.

I believe a Lambda senso should only go to a max voltage of 0.9v so maybe its faulty.

I don't think I'm going to be able to test the sensor regards counting the needle fluctuations as the procedure seems to be stated wrongly in the Toyota manual.

Has anyone here managed to test the sensor in this way?

Bridging TE1 and E1 puts the engine mangement into certain modes. It allows the reading of trouble codes from the management light flashing whilst the ignition is on but not running. It also sets the engine to idle between 1000 and 1300 when bridged whilst running for setting the ignition timing with a strobe.

[Mr2Owner]

Ok, the car didn't like it when I bridged TE1 + E1 with the car running, as soon as I bridged them terminals, the engine revs raised and the engine management light was on.

So I just checked the voltage from VF1 and E1 again and its at 3volts approx at 2500rpm then drops to 0.10 when ideling.

I believe a Lambda senso should only go to a max voltage of 0.9v so maybe its faulty.

I don't think I'm going to be able to test the sensor regards counting the needle fluctuations as the procedure seems to be stated wrongly in the Toyota manual.

Has anyone here managed to test the sensor in this way?

Bridging TE1 and E1 puts the engine mangement into certain modes. It allows the reading of trouble codes from the management light flashing whilst the ignition is on but not running. It also sets the engine to idle between 1000 and 1300 when bridged whilst running for setting the ignition timing with a strobe.

That explains why the engine revved up then so. I knew that bridging them terminals with the engine off was for reading fault codes but didn't know about setting the ignition timing and raising the revs. Thanks for the info.

This contradicts the info in the Toyota lambda sensor test procedure of bridging them terminals, whats the point in bridging them if its going to set the engine revs at 1000-1300 when the lambda test then goes on to say rev the car at 2500rpm. That whole lambda test doesn't seem to make any sense.

Think ill just buy a new sensor!

[abovetherim]

I'm only guessing here but i assume that bridging those ports sets the ecu into open loop i.e. a set fuel map with no adjustment on the mixture or timing. So at 2500 rpm the output of the o2 sensor should be within a known range.

[mr2magic]

1) The lambda value youre seeing there is interpolated by the test apparatus - and is based on the other values being read so forget it. Once the other values are within range, the lambda will follow.

2) High CO values have a couple of possible reasons
a) low idle rpm
b) bad o2 sensor
c) bad cat
d) Rich mixture due to
* clogged air filter
* leaking fuel injection
* cold start injector not switching off

[Mr2Owner]

1) The lambda value youre seeing there is interpolated by the test apparatus - and is based on the other values being read so forget it. Once the other values are within range, the lambda will follow.

2) High CO values have a couple of possible reasons
a) low idle rpm
b) bad o2 sensor
c) bad cat
d) Rich mixture due to
* clogged air filter
* leaking fuel injection
* cold start injector not switching off

That's a helpful check list of things to check/rule out.
What do you mean by "interpolated" and by apparatus do you mean the multimeter?

a - low idle rpm - Seems normal, think from memeory its about 850rpm, is that normal?
b - bad O2 sensor - Thats what I'm trying to test, Are you saying theres no way to test the sensor so forget it?
c - bad cat - The cat was bad, replaced with what seemed like a good 2nd hand cat, emissions have been reduced greatly with new cat. Maybe it's just not as bad as the old one?
d - rich mixture
* Clogged air filter - Good point, car has a aftermarket cone filter which doesnt look the cleanest, I'm trying to source a standard air housing, Ill clean the cone filter in the meantime.
* Leaking fuel injection - I don't think this is a problem but can't say for 100%. The car seems to drive fine in every way
* Cold start injector not switching off - Not sure if it is or not, but haven't noticed any bad running

[mr2magic]

when i say the lambda us interpolated i mean it's a value not being measured by the tester used wherever you treid to mot it. i know of no tester which actually has an o2 Sensor in it. Now that doesn't mean none have a sensor but i know the older bosch don't.

No an o2 sensor can be tested as noted previously in the thread. You can either backprobe it using its ground and signal wires or remove it and use a torch or similar to heat it and check the readings in free air. I have had good experience using sensors from unifit here in germany if you need a replacement.

the filter isn't usually a problem. Cracked and worn injector o-rings are hard to spot and relatively commonplace.

[Mr2Owner]

when i say the lambda us interpolated i mean it's a value not being measured by the tester used wherever you treid to mot it. i know of no tester which actually has an o2 Sensor in it. Now that doesn't mean none have a sensor but i know the older bosch don't.

No an o2 sensor can be tested as noted previously in the thread. You can either backprobe it using its ground and signal wires or remove it and use a torch or similar to heat it and check the readings in free air. I have had good experience using sensors from unifit here in germany if you need a replacement.

the filter isn't usually a problem. Cracked and worn injector o-rings are hard to spot and relatively commonplace.

Are you saying you can't test the sensor the way its outlined in the Toyota manual counting the needle fluctuations representing the sensor going from 0.1v to 0.9v range.

To check the resistance of the 4 wire sensor, which 2 wires are you checking, the 2 heater element wires?

[mr2magic]

no, I'm saying you can test it that way. Just do exactly as the bgb states and you'll be fine. Don't overcomplicate the test - it's all very straightforward

[SonicSW20]

1) The lambda value youre seeing there is interpolated by the test apparatus - and is based on the other values being read so forget it. Once the other values are within range, the lambda will follow.

Well, that depends on what the problem is. You can pass CO and HC, but fail on the measured lambda if you have an exhaust leak after the cars o2 sensor that's introducing additional air into the exhaust. While the car will continue to read fine as it won't see the additional air, the measured lambda will be significantly above 1 due to the additional oxygen. It's not accurate to just disregard it.