Alfa Pages

gritsop · Posted: Sun Jun 05, 2005 10:49 am Post subject: lambda sensor

Hi,

Reaching 100.000 kms and suspecting that the antipollution system does not function as it should, I made some measurements based on the manual's readings.

I should note that the car passes the exchaust test marginally, according to the mechanics words and catalyst & lambda sensor should be replaced in the next years exchaust test.(never replaced lambda sensor & catalyst)

However I have measured the voltage in the lambda sensor connector and also the presense of voltage in the heating element of it.

The voltage between lambda probe and earth fluctuates between 0.450 - 0.600 V and 12V in the preheating resistance which has a 4.8 Ohm resistance.

The car is warmed up to 100 degrees and the reading of lambda probe voltage does not fall below 0.450 V

According to the manual the voltage should be 0.030 - 0.001 V (30mV - 1mV).

Could someone with new or relatively new lambda sensor do a test on its own car about these readings?

Or if advise is more easy, it is welcome. By the way it is a Jetronic LE 3.2 management system.

The pic below shows you the connectors involved.

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

Harri · Posted: Mon Jun 06, 2005 6:11 am Post subject:

O.45 V is what should be the average reading. It should fluctuate quite rapidly, about once per second from rich to lean (under 0.45=lean, above=rich). If there is no rapid fluctuation then it might be time for a new sensor. Are you sure it says 0.03-0.001V in the manual? Shocked

Must be a typo...

My 33 16V has 212k kms on the clock with the original lambda sensor and cat. It is very important to get the cat well heated before inspection though, otherwise it will not pass. Last time CO%=0.001 and HC=20 but let's see what the figures are in a couple of weeks when it is time for the next check up.
_________________
1990 33 16V QV
1993 164 QV 24V
1989 164 3.0 V6
2003 156 JTS Selespeed SW

gritsop · Posted: Mon Jun 06, 2005 9:13 am Post subject:

Hi,

Thanks for the reply.

Yes , the manual says so, but a research on the web revealed an average of 0.45V as you said. Maybe it's a typo error on the manual.

Did again a test after a 15km ride and the voltage of the connector revealed around 0.720 V which tends towards rich mixture ...

However the readings I got were fluctuating around the 0.7 V . Within a couple of seconds it could go from 0.718 to 0.723 and so on - but not dropping less that 0.7 V.

Next step will be removing it and give it a good cleaning to see if this makes a difference. Do you know a way to clean it without damaging it?

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

tvatavuk · Posted: Mon Jun 06, 2005 9:25 am Post subject:

Hi Gristop,

I hope that you measured readings with lambda probe connected to ECU while car was running.

BOSCH lambda probes fitted to our Alfas are known for their slow/lazy change in readings.
And with time passing exhaust particles stick to lambda intake grooves and make lambda probe reading even slower, less exhaust gases enter to sensor.
There are carb cleaner sprays that should be lambda and catalytic converter frendly, don't know if it means that they are only ok for them after burning in cylinder, but what can you loose if lambda allready doesn't work.
A week ago I replaced mine on my 16v because it was showing even narrower reading then yours and it had big dent (you could hear broken ceramic rattle inside it). I bought BERU universal replacement probe (60% of price of original BOSCH), with that one readings were jumping from 0.6-1.0 and back.

And then struck Murphy law.
Last friday first viscous coupling rubber mount failed, it had to be left one so visco coupling fell down and BANGed nicely on brand new probe Sad

Now I'm glad I didn't bough original first time, because now cost would be even higher.
_________________
Tino Vatavuk
Little black dress which replaced Alfa Romeo 33 S 16v Permanent 4 GMo

gritsop · Posted: Tue Jun 07, 2005 1:37 pm Post subject:

Hi,

Thanks guys for the input. I have already ordered a new sensor, so tomorrow I 'll have it on hands.

But yet another question. Should the fluctuation in the current the probe gives, ( + or - around 0.45V) be in idle or in higher revs?.

The measurements I did again were:

around 0.45 when cold and idle
around 0.78 when hot (including a 8 km) ride and idle

rapid fluctuation from 0.1 to 0.6 when around 3000 rpms.

Any help?

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

tvatavuk · Posted: Tue Jun 07, 2005 2:17 pm Post subject:

Rapid fluctuation around 3k rpm from 0.1-0.6 could be TPS in case 1.4 IE has it.
On 16v it disables lambda after 3-3,5rpm. (or to put it correctly if throttle position is higher then some amount).
when warm and giving throttle few bursts to 4-5k rpm, labda probe reading should oscilate enough to jump from rich to poor and back (0.6-1.0) trying to compesate fuel mixture.
Are you using original paper air filter?
_________________
Tino Vatavuk
Little black dress which replaced Alfa Romeo 33 S 16v Permanent 4 GMo

gritsop · Posted: Tue Jun 07, 2005 3:29 pm Post subject:

Hi,

1.4 IE has a minimum / maximum throttle switch instead of a TPS, it recognises open or close condition of the throttle.

Yes, I do use the original paper air filter.

Any idea?

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

tvatavuk · Posted: Tue Jun 07, 2005 3:45 pm Post subject:

I would play with min/max switch to see its effect on lambda readings.
But besides that none whatsoever.
_________________
Tino Vatavuk
Little black dress which replaced Alfa Romeo 33 S 16v Permanent 4 GMo

gritsop · Posted: Tue Jun 07, 2005 4:06 pm Post subject:

Hi,

Actually, accelerator pedal acts on this switch which when revving, the lambda readings fluctuate as I described above.

I had today the lambda removed, it was clean without black deposits or exchaust particles blocking the grooves. However the sensing element was kind of white colored. Cleaned it with petrol but no difference in the readings.

Anyway I'll have it replaced tomorrow and if anyone has any idea, it is welcome.

Regards,
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop

gritsop · Posted: Thu Jun 09, 2005 9:16 pm Post subject:

Hi,

After all I fitted a new lambda sensor and took the readings. They are better and it appears that it is warmed up faster.

The first few seconds of the engine running on the new sensor were kind of erratic but afterwards all sounded ok.
The car now feels better in response with no signs of "hesitation" in acceleration.

However the exchaust fumes have not been as expected. Of course the lambda ratio is excellent; CO & HC at 2500 rpm is perfect BUT CO at idle is high, about 2 units (should be less than 0.5)... Confused

Anyway, I 'll see what anything more can be done.
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
Parts Shop: www.alfa-restoration.co.uk/shop