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Lambda Sensor Behavior


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#1 tmsmini

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Posted 03 April 2021 - 06:12 PM

I just recently started looking at the logs from an MPi MEMS 2J engine using RoverMEMS.

The lambda sensor is not a Bosch and I have ordered what is supposed to be a Bosch brand, but so was the one I am using.

 

After the engine warms up and goes into closed loop, the sensor fluctuates high/low for about five minutes. After five minutes, the fluctuation becomes smaller and smaller tending toward high. After awhile it becomes stuck at the high end or with marginal voltage shift.

 

Anyone else seen this behavior?



#2 genpop

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Posted 04 April 2021 - 06:39 AM

Hi tmsmin

have a look to this thread:https://www.theminif...-broken-sensor/

possibly it will help with your problem!



#3 tmsmini

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Posted 04 April 2021 - 06:17 PM

I have reviewed that thread.

The original part number MHK10004 as provided by Rover was a Bosch product with a separate Bosch code engraved on it.

At some point these dried up. Minisport had a great deal on original Rover/Bosch sensors at some point and I bought several.

What ever is being called MHK10004, may not be up to the orginal specification and who know who makes it. Even when you ask if it is a Bosch version you may be told it is when there are no part numbers engraved.

 

Finding a Bosch replacement in the US is next to impossible. I have another part number to try.

If you look for 0258 003 193 in the US, you will get cross referenced to another part number.

Once I try it, I will report back.



#4 tmsmini

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Posted 04 April 2021 - 07:50 PM

Not sure why I saved this, but  still have a used version.

 

I do not understand all the disticntions between narrowband lambda sesnors, but this has a LSH-6 formula.

The replacement Bosch versions I have received have a different LSH "formula."

 

Attached Files



#5 genpop

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Posted 05 April 2021 - 06:12 AM

Just check with an ohm-meter if there is connection between slate and ground.If yes its original Bosch or a good replacement.

Attached Files



#6 tmsmini

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Posted 05 April 2021 - 11:04 PM

The old one in the picture is properly grounded. I will test the unmarked version when I swap.



#7 tmsmini

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Posted 15 April 2021 - 09:12 PM

Following up on this, I am still more confused than before.

The sensor in the car was one of the Rover/Bosch versions. This is a MEMS 2J ECU.

 

After trying to get information from Bosch USA on a suitable substitute, I was directed towards 0258986506(15727) as a substitute.

Bosch USA was not too interested in finding a part for a European market car, but suggested based on the original Boasch part number this would be compatible.

 

I installed it and it seems to be working...but...

 

It appears to have the behavior of the old Rover/Bosch sensor I thought was bad.

 

I have attached a log. It is formatted as a CSV but labelled as TXT.

At row 713, the system appears to go to closed loop

At row 7665, it appears to go to open loop(approximately five minutes time)

At row 6904 the O2 value changes from 2006 to 3476 and stays high after that.

 

It seems there is something else going on.

Attached Files


Edited by tmsmini, 15 April 2021 - 10:18 PM.


#8 sonscar

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Posted 16 April 2021 - 06:59 AM

My limited understanding is the closed loop is activated by the ECU based on engine temp,Map,rpm and throttle position.The llambda is then allowed to alter the fuelling to keep it stoich.As you say maybe the llambda is correct and there is another problem.Good hunting,Steve..

#9 genpop

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Posted 16 April 2021 - 09:47 AM

hi tmsmini,

is that a wideband sensor?

The Bosch people will not give information  as well not in Germany.

As far as I know, Chevy van with 4.3  l engines from1993 had a lambda probe with earth connection too.



#10 tmsmini

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Posted 16 April 2021 - 01:41 PM

It is a narrowband sensor.

Disappointing about Bosch. Many years ago you could find all sorts of specifications on VDO/Bosch components including the intank pumps used on SPi and MPi.

 

I think one of the cars listed for the sensor they suggested was a 1999 Jeep.



#11 genpop

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Posted 16 April 2021 - 02:18 PM

I converted an AMC jeep CJ7  year 77 from carburator to TBI.Therefore I had the ecu from the Chevy,( the Caprice had the same one ) a 1613965.This ecu needed the earth connected to ground like the schematic i gave you. But originally this earth was token by the lambda therefore I think their lambdas will work too.



#12 tmsmini

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Posted 16 April 2021 - 04:19 PM

The 15727 sensor(as labelled in the US) do have the ground as indicated.

I will do some more testing today and make an update if i find anything.



#13 tmsmini

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Posted 17 April 2021 - 12:13 AM

I tried logging with the Android app today. It seems the format is different.

It does look like the MAP values are high as well as the odd behavior of the lambda sensor.

I cleaned the MAP sesnor although it is standalone on an MPi with no fuel trap.

I swapped the IAC for a clean version.

I reset the stepper with the ACR. Although the value does not seem stable.

I checked for leaks around all the sensors and hoses as well as the intake manifold.

It idles happily and the fan comes on at the appropriate time. I had replaced the temp sensor recently.






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