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[Entwood]

No leaks apparent, done the carb cleaner trick, nothing found. Unplugged the lambda and it gave fault code 0170 as expected. plugged back in and cleared faults. engine not running S1 voltage is 0.45 as soon as engine is running in closed loop it drops to 0.075 and stays there. No faults shown

Lambda was changed 5 days ago for MOT emissions failure. Engine was NOT rough before then but is certainly rough now. Resistance from lambda body to engine block is 20 ohms.

Open loop to closed loop takes about 2-3 minutes

Am I being daft in thinking a faulty lambda has been fitted ?? are there any checks I can do on the lambda sensor

[Entwood]

Car was running fine until 5 days ago when code 0170 and MOT fail for emissions so lambda 1 changed. 0170 went away but car barely passed retest on emmisions.

Tom now on his way home to put the old lambda in, and (hopefully) return so we can check the readings to see what, if anything changes. Hopefully at least we'll see the old one switching which the new one doesn't.... he'll then take the (suspect) new one back and try and change it.

Does this sound like a plan ??

[tommy mac]

Changed the lambda sensor back to the old one and straight away it came back with the P0170 error code.  I think I must becoming super sensitive to the sounds of the engine but tickover still seems a little rough.   Anyway back to Nige's now to put it on his meter and see what gives.


Tom 

[Entwood]

Next set of numbers .. from the "old" sensor ...

SHRTFT1 - 0.0
LONGFT1 - 11.7
RPM 754
ADV 6-8 degrees
MAF 2.49 - 2.59 slow cycle
TP 3.1

O2B1S1  - 0.055
O2B1S2 - 0.075
SHRTFTB1S1 - 0.0

So very little difference. Tom says the car seems to "hang" at various rpm's .. so tried stepping up through the rev range .. definite hang at 4000 rpm for about 2 secs then it accelerates through. Holding RPM at 2000 B1S1 starts to cycle VERY slowly. After holding 2000 RPM for 2 minutes the system went to OL_FAULT and the "hang" at 4000 rpm had gone , although the engine still is not smooth in any way !!!

Given that BOTH sensors fail to "cycle" I'm more and more convinced that the "new" sensor is faulty .... any ideas gratefully accepted

Another hypothesis .... sensor heater circuit not working of the 4 wires which are the heater ones .. we can then stick a meter across and check for a voltage at least !! Heater circuit failure "should" give a fault code though I think ??

[Marks DTM Calib]

And the coolant temperature sensor reading is.....

[Marks DTM Calib]

MAF reading is still pretty low.

And P0170 is a fuel trim malfunction and not neccassarily an O2 sensor code.

[Entwood]

MAF reading is still pretty low.

And P0170 is a fuel trim malfunction and not neccassarily an O2 sensor code.

When we unplug the Lambda the P0170 comes up straight away, and the S1 is not switching on either sensor ??

[Marks DTM Calib]

Which makes me think that the MAF is giving a low reading (which it is), the ECU is applying fuel quantity based on MAF value and hence constant lean mix......all assuming its closed loop.

[Entwood]

Which makes me think that the MAF is giving a low reading (which it is), the ECU is applying fuel quantity based on MAF value and hence constant lean mix......all assuming its closed loop.

But whatever the actual fuel the S1 should switch at 1hz I thought ?? However .. would unplugging the MAF achieve anything ?

Engine temp off my reader is 80 C

[Entwood]

OK MAF unplugged

ETC 80 C
SHRTFT1 5.5
LONGFT1 11.7
RPM 871
Adv 5 deg
O2B1S1 .250 static
SHRTFTB1S1 5.5
O2B1S2 0.370

Car & Spanner light on, no codes on MIL

Engine runs without missing and accelerates throughout the range with no hesitation at all (not tried underload however)

Could it be 2 problems ?? MAF incorrect and Lambda not switching

[Entwood]

Tom's driving home with the MAF disconnected to see the effect under load .....

[tommy mac]

Yep- drove home with the MAF disconnected and it was almost a relief as it was certainly much smoother even if the power was clearly down.

I think I'll get my hands on a MAF sensor and see what that does....if it doesn't change anything then I have reached step 2 of being an Omega owner.............building a collection of working sensors to compare with the ones on the car

It's been an interesting experience so far and it has improved my understanding of the systems no end.  Any thoughts following on from Nige's data are welcomed and many thanks to those responding.


Tom

[henryd]

Next set of numbers .. from the "old" sensor ...

SHRTFT1 - 0.0
LONGFT1 - 11.7
RPM 754
ADV 6-8 degrees
MAF 2.49 - 2.59 slow cycle
TP 3.1

O2B1S1  - 0.055
O2B1S2 - 0.075
SHRTFTB1S1 - 0.0

So very little difference. Tom says the car seems to "hang" at various rpm's .. so tried stepping up through the rev range .. definite hang at 4000 rpm for about 2 secs then it accelerates through. Holding RPM at 2000 B1S1 starts to cycle VERY slowly. After holding 2000 RPM for 2 minutes the system went to OL_FAULT and the "hang" at 4000 rpm had gone , although the engine still is not smooth in any way !!!

Given that BOTH sensors fail to "cycle" I'm more and more convinced that the "new" sensor is faulty .... any ideas gratefully accepted

Another hypothesis .... sensor heater circuit not working of the 4 wires which are the heater ones .. we can then stick a meter across and check for a voltage at least !! Heater circuit failure "should" give a fault code though I think ??

Black is signal,grey is earth,both whites are heater

[Webby the Bear]

Yep- drove home with the MAF disconnected and it was almost a relief as it was certainly much smoother even if the power was clearly down.

I think I'll get my hands on a MAF sensor and see what that does....if it doesn't change anything then I have reached step 2 of being an Omega owner.............building a collection of working sensors to compare with the ones on the car

It's been an interesting experience so far and it has improved my understanding of the systems no end.  Any thoughts following on from Nige's data are welcomed and many thanks to those responding.


Tom

i'd try cleaning it first with electric contact cleaner. I know people on here don't favour it but it worked for me. worth a try if you were going to swap it anyway imo 

[Marks DTM Calib]

Contact cleaner won't work on the first film type MAFs (it does on the old hot wire ones).

Of the MAF is causing a lean mix then the lambda won't switch