Replacing Lamda Sensor SL320 1997

[Graham Stevens]

Local Merc Specialist has had my car on the diagnostics machine and it would appear that the reason for the engine partial cutout above 4000rpm is due to the air mass meter and the oxygen sensor not working. The engine runs beautifully up to 4000rpm by the way. They suggested that the air mass meter failure could have some bearing on the oxygen sensor failing so to replace that first.
So I did and it has not made any difference at all. So now the oxygen sensor - is this a job I can do myself? I've located the part (why are there 2?) on the ignitioncarparts website but have no idea where it (they) are located under the bonnet. Can anyone help ?

 

[stats007]

They're located in the exhaust system:

Numbers 92 and 95 - pre and post CAT?

 

[television]

Local Merc Specialist has had my car on the diagnostics machine and it would appear that the reason for the engine partial cutout above 4000rpm is due to the air mass meter and the oxygen sensor not working. The engine runs beautifully up to 4000rpm by the way. They suggested that the air mass meter failure could have some bearing on the oxygen sensor failing so to replace that first.
So I did and it has not made any difference at all. So now the oxygen sensor - is this a job I can do myself? I've located the part (why are there 2?) on the ignitioncarparts website but have no idea where it (they) are located under the bonnet. Can anyone help ?

Its no good just reading fault codes and replacing the faulty itms shown.

You have 3 things shown on the diagnostic read out, you need to work out that If the MAF is on the way out,then other components try and compensate by changing from their stored settings, thats all the diag tells you, and you have now found that out by changing the sensor.
The MAF is the one to change here.

The fault codes do not tell you what is faulty, it assumes that you have a knowledge of what you are doing.

Malcolm

 

[stats007]

I presume the diagnosis displayed sensor readings that were out of range implying faulty components.

 

[type49]

I presume the diagnosis displayed sensor readings that were out of range implying faulty components.

Exactly. Only them being out of spec doesnt always mean they are faulty. As TV says, one item is probably faulty and the others are out of spec because of it. Air mass sensor, or MAF as everyone calls it, is the most likely and easiest thing to change.

 

[Graham Stevens]

Sorry - my word order was a bit ambiguous - it is the Air Flow Meter that I have already replaced. I have no idea what the diagnosis sensor readings were - I am pretty new to running older cars with 'plug-in diagnostics and I obviously made the mistake of assuming that whatever the 'Specialist' suggested was likely to be accurate - the asking price for them to do it was huge though which is not reflected in the parts prices I now find! So do I go ahead and replace the lamda sensors or run it for a while and see if they change their stored settings?

 

[television]

I presume the diagnosis displayed sensor readings that were out of range implying faulty components.

That is correct, When I bought my car, the only thing not working was the comfort seats. MB in liverpool and an Indie down here said after the diag "leak in drivers cushion" The thing that puzzled me was the fact that the PSE pump did not run when the seat buttons were pressed. I took out the pipe from the pump and blew the seats up, and they both stayed up for 4 days. I had a chat to MB in Exeter and they let me go through with their best man, their diag showed air leak in drivers seat. after explaining that the pump was not running, deep in the menu, there it was "not activated"

I do not know what other people do to get through it. I had read every bit of info that I could find, others cant do that. It is getting worse, as the MB man said,if it shows on the diag,we have to change it to stop come backs.


malcolm

 

[eric242340]

Sorry - my word order was a bit ambiguous - it is the Air Flow Meter that I have already replaced. I have no idea what the diagnosis sensor readings were - I am pretty new to running older cars with 'plug-in diagnostics and I obviously made the mistake of assuming that whatever the 'Specialist' suggested was likely to be accurate - the asking price for them to do it was huge though which is not reflected in the parts prices I now find! So do I go ahead and replace the lamda sensors or run it for a while and see if they change their stored settings?

The 02 sensors only tell you on diag that there is an air/fuel ratio problem. Changing the oxygen sensors does not cure the problem. The new sensors would show the same fault code. And I quote Malcolm (TV) on this one (we change parts to avoid combacks) what a sorry world we live in when mechanics make statements like this. You have two potentials on this one; a. an air leak. b. carbonized fuel injectors.

 

[Graham Stevens]

OK, thanks for that, I guess I'll have to check for air leak and/or for carbonised fuel injectors next. This car only gets used March to October so I have a little time to play with yet.
Graham

 

[stats007]

The 02 sensors only tell you on diag that there is an air/fuel ratio problem. Changing the oxygen sensors does not cure the problem. The new sensors would show the same fault code. And I quote Malcolm (TV) on this one (we change parts to avoid combacks) what a sorry world we live in when mechanics make statements like this. You have two potentials on this one; a. an air leak. b. carbonized fuel injectors.

This is correct providing the O2 sensors are not at fault themselves - supplying in range readings that are incorrect will cause the engine to over/under fuel accordingly.

 

[Pipemaster]

Local Merc Specialist has had my car on the diagnostics machine and it would appear that the reason for the engine partial cutout above 4000rpm is due to the air mass meter and the oxygen sensor not working. The engine runs beautifully up to 4000rpm by the way. QUOTE]
I had a problem with mine last week at around 31/2 to 4k revs, which turned out that the replacement MAF was faulty and when replaced again and run for a whikle the ignition remapped itself and now I dont have the probelm. Not meaning anything but as you say you don't run the car all year, have you driven round for say half an hour after the new MAF was put on to give it change to remap. Mine ran like a bag of nuts for the first run and then after being left and run again it was sorted. Perhaps this could work with yours?
BTW the previsou owner had chnaged the cats and the lambda sensors in october which clearly didnt sort the porblem which means I agree with Malcolm says about the MAF is correct.
Hope it helps

 

[kth286]

Graham

Is your car the the 129.063 (straight 6) or

129.064 (V6).

When the engine would not go above 4000 revs, was that stationary, or were your driving it ?

 

[television]

Pipemasters 129 is a 064 car, the V6 was standard from 08 98 on.

Malcolm

 

[stats007]

Pipemasters 129 is a 064 car, the V6 was standard from 08 98 on.

Malcolm

Indeed Malcolm, but Graham's is a 129.063 straight six.

 

[television]

Indeed Malcolm, but Graham's is a 129.063 straight six.

Read the question wrong, and i dont drink.

Malcolm

 

[kth286]

Graham

If your car is the 'straight 6' then there is only one Lambda sensor and it is screwed into pipe just in front of the cat.

Give your VIN number to get the correct sensor.

As far as only revving to 4000, then if you were driving the car it had probably gone into 'limp home' mode.

BUT, if the car was stationary, and you were revving the engine, then it hit the safety cut out for an unloaded engine.

 

[television]

Graham

If your car is the 'straight 6' then there is only one Lambda sensor and it is screwed into pipe just in front of the cat.

Give your VIN number to get the correct sensor.

As far as only revving to 4000, then if you were driving the car it had probably gone into 'limp home' mode.

BUT, if the car was stationary, and you were revving the engine, then it hit the safety cut out for an unloaded engine.

A 97 129 is a 163

malcolm

 

[eric242340]

Graham

If your car is the 'straight 6' then there is only one Lambda sensor and it is screwed into pipe just in front of the cat.

Give your VIN number to get the correct sensor.

As far as only revving to 4000, then if you were driving the car it had probably gone into 'limp home' mode.

BUT, if the car was stationary, and you were revving the engine, then it hit the safety cut out for an unloaded engine.

Totally agree with the drive in park, rev the engine it reaches 4k then dies back, if holding the throttle on the floor it will drop below 4k and the come back. Fuel safety shut off for unloaded engine. Perfectly normal. But if they are telling him to change the MAF, then he probably means it dies at 4K when in drive.

 

[Graham Stevens]

Final Comment - Took the car out again today, let it warm up for a few minutes first, now works perfectly again, perhaps the oxygen sensors have 'reset' themselves. So it was the Air Flow Meter after all. Thanks for all the help and advice. Graham