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Author Topic: Lambda question  (Read 4665 times)

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tigers_gonads

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Lambda question
« on: 30 July 2018, 13:15:49 »

Am I right in thinking that on a 3.2, its the 2 front sensors that do the work with the idle fuel trims ?

Both now seem to be very slow with neither switching the full range between 0 and 1000mV regardless of engine temperature  :(
MOT due in a couple of months and its been a close run thing for the past few years on emissions


If so, were is the best place to get them ?


TIA  :)
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Marks DTM Calib

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Re: Lambda question
« Reply #1 on: 30 July 2018, 13:32:25 »

If both are slow to change its unlikely to be the sensors, hows the MAF?

But yes, its the front two  :y
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Re: Lambda question
« Reply #2 on: 30 July 2018, 13:44:06 »

If both are slow to change its unlikely to be the sensors, hows the MAF?

But yes, its the front two  :y



Hi Mark  :)

Its been throwing up very occasional Bank 1 faults when the car is cruising / very light pedal at say 50mph ish.
That sensor was slow.
Now the other bank is getting that way too.

Using that laptop based software which we never mention  :-X, the MAF is reading between 16 and 19 at idle depending on temperature  :-\

Other then that, the cars running great and doing pretty good on fuel considering my right foot  ;D


I do know the battery has seen a lot better days so that is sucking up a lot of the charge from the alternator if whatever it is is voltage related  :-\

Also the air filter is new / breathers are clear / no air leaks apparent
« Last Edit: 30 July 2018, 13:47:33 by tigers_gonads »
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Re: Lambda question
« Reply #3 on: 30 July 2018, 16:00:23 »

Has the lpg been recalibrated recently?
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tigers_gonads

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Re: Lambda question
« Reply #4 on: 30 July 2018, 16:56:03 »

Has the lpg been recalibrated recently?


Yup  :y
MAP pressure tweeked down to around 1.1 bar and gas map tweeked a couple of weeks ago.
Just had the Stag software running on it and everything is spot on with the exception of a few codes, all pointing towards voltage problems on lpg injectors accross both banks  :-\


The more and more I look at it, the more I am thinking voltage.

With the power amp added to the audio setup, that's going to pull volts away from the car systems too  :-\

Anyway, with all engine sensors requiring a stable voltage to make the engine properly and with the battery at least 4 years old to my knowledge, i've let Europarts relieve me of 45 quid for a new battery which hopefully is ariving tomorrow.


Not saying thats the cure but I know its not in the best of condition and its another thing out of the equation  :y


Also just to clarify, the latest set of codes came with he car running on LPG and petrol  :( due the lack of LPG stations in darkest Lincolnshire  :'(   
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Re: Lambda question
« Reply #5 on: 30 July 2018, 20:16:26 »

You could try a 140 amp alternator...

Follow Kevins starting/charging test and go from there :y
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tigers_gonads

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Re: Lambda question
« Reply #6 on: 30 July 2018, 23:09:36 »

You could try a 140 amp alternator...



Might have to look into that one depending on cost  :-\

Follow Kevins starting/charging test and go from there :y




Been through it a few times over the last year or so.
All crimps are solid / cold ect  :-\

Not got much work to do so if I get chance in morning, i'll get the front up and check the block to chassis bonding straps  :y
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Re: Lambda question
« Reply #7 on: 31 July 2018, 07:28:34 »

You could try a 140 amp alternator...



Might have to look into that one depending on cost  :-\

Follow Kevins starting/charging test and go from there :y




Been through it a few times over the last year or so.
All crimps are solid / cold ect  :-\

Not got much work to do so if I get chance in morning, i'll get the front up and check the block to chassis bonding straps  :y
And you're a Sparky ::)

What does the data tell you amps on vs amps off?
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tigers_gonads

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Re: Lambda question
« Reply #8 on: 31 July 2018, 08:35:27 »

You could try a 140 amp alternator...



Might have to look into that one depending on cost  :-\

Follow Kevins starting/charging test and go from there :y




Been through it a few times over the last year or so.
All crimps are solid / cold ect  :-\

Not got much work to do so if I get chance in morning, i'll get the front up and check the block to chassis bonding straps  :y
And you're a Sparky ::)

What does the data tell you amps on vs amps off?




Tbh, I haven't really looked into it that deep  :-[
It always starts first time (abet turning over slowly)
Its not too bad on fuel when you take into account the price of lpg.
Insurance is cheep.
Other then oil changes twice a year (3 1/2 - 4K), consumables / changing any filters that look grubby, its pretty painless motoring  :-\
At the end of the day, it gets me were I want to go with a smile on my face when the dog isn't in the back and doesn't cause me many problems at MOT time so if it ain't costing me extra money, these little niggly faults get stuck on the back burner  :-\


Then again, the list of niggly bits IS getting rather long now  :(
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Re: Lambda question
« Reply #9 on: 31 July 2018, 09:51:42 »

I would say the supply voltage would have to be a long way below par to cause problems. All the sensor circuits in the ECU operate from an internally generated 5V regulated rail so unless the supply is low enough for that to drop out of regulation it will be fine.

I would have a look at the live data and see what the fuel trim values do after start up. You should see both lambda sensor values cycling and the short term fuel trims moving after a minute or two of idling.

If the lambda sensors seem lazy, let it warm up fully and then hold it at 3000 RPM for a minute or so. This should wake them up. They should stay toggling when the engine returns to idle but if on or other dies again after a little idling, it could be time to swap the sensor.

Obviously, if the fuel trims head off to oblivion, something else is wrong. They should stay within a few percent of zero on petrol. LPG might be another matter.
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Re: Lambda question
« Reply #10 on: 31 July 2018, 09:53:34 »

All 4 sensors are the same*, so you can swap them around to try to trace a faulty sensor. Getting them unscrewed might be the biggest challenge there, however.

* -  cable length varies a little between pre-cat and post-cat sensors but they still reach with care.
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Re: Lambda question
« Reply #11 on: 31 July 2018, 10:13:15 »

I would say the supply voltage would have to be a long way below par to cause problems. All the sensor circuits in the ECU operate from an internally generated 5V regulated rail so unless the supply is low enough for that to drop out of regulation it will be fine.

I would have a look at the live data and see what the fuel trim values do after start up. You should see both lambda sensor values cycling and the short term fuel trims moving after a minute or two of idling.

If the lambda sensors seem lazy, let it warm up fully and then hold it at 3000 RPM for a minute or so. This should wake them up. They should stay toggling when the engine returns to idle but if on or other dies again after a little idling, it could be time to swap the sensor.

Obviously, if the fuel trims head off to oblivion, something else is wrong. They should stay within a few percent of zero on petrol. LPG might be another matter.


Is that regulated in the engines ecu Kev ?

How much can it compensate if the voltage is marginable (say 13 volts) and the car is having to service a reasonably large electrical load. i.e. large  audio amp / fan / lights ect ?


I know what you mean about the 4 sensors but in reality, I have never managed to get one out in one piece yet  :-[
In fact I normally just smash the thing up and stick a long reach socket on it c/w strong arm  ::) 
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Re: Lambda question
« Reply #12 on: 31 July 2018, 10:20:16 »


I know what you mean about the 4 sensors but in reality, I have never managed to get one out in one piece yet  :-[
In fact I normally just smash the thing up and stick a long reach socket on it c/w strong arm  ::)


Using an oxy-acetylene torch, heat the socket the sensor screws into to red-hot and let it cool. Do this a couple more times, then unscrew the sensor while the socket is still red-hot.
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Re: Lambda question
« Reply #13 on: 31 July 2018, 10:33:59 »

Using an oxy-acetylene torch, heat the socket the sensor screws into to red-hot and let it cool. Do this a couple more times, then unscrew the sensor while the socket is still red-hot.

We managed the same with just a regular gas torch while swapping the exhaust on a mates Gallardo last weekend (it takes a special kind of crazy to change your own exhaust & CATs on a car like that ;D).. as T_G probably doesn't have an acetylene setup knocking about (wish I did, but it scares the wotsit out of me, so I don't!)

I would say the supply voltage would have to be a long way below par to cause problems. All the sensor circuits in the ECU operate from an internally generated 5V regulated rail so unless the supply is low enough for that to drop out of regulation it will be fine.

I would have a look at the live data and see what the fuel trim values do after start up. You should see both lambda sensor values cycling and the short term fuel trims moving after a minute or two of idling.

If the lambda sensors seem lazy, let it warm up fully and then hold it at 3000 RPM for a minute or so. This should wake them up. They should stay toggling when the engine returns to idle but if on or other dies again after a little idling, it could be time to swap the sensor.

Obviously, if the fuel trims head off to oblivion, something else is wrong. They should stay within a few percent of zero on petrol. LPG might be another matter.


Is that regulated in the engines ecu Kev ?

How much can it compensate if the voltage is marginable (say 13 volts) and the car is having to service a reasonably large electrical load. i.e. large  audio amp / fan / lights ect ?

I'm with Kevin on this - the only time I've seen voltage induced problems is either:
1) Ignition systems on old cars with a coil & distributor, when the voltage is <12V
2) More modern cars when the alternator packs up and pushes >17V or <9V into everything and the dash lights up like a Christmas tree (BMW!)

If you're anywhere in the region of 12V (12-15V) everything will cope just fine, albeit at the bottom end the battery will slowly go flat!
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Re: Lambda question
« Reply #14 on: 31 July 2018, 11:29:42 »

Yep, the voltage probably dips to 9V when you start the car, so it is designed to cope with this at the very least.

Other things like the ABS and automatic gearbox will throw in the towel long before the engine ECU.
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Re: Lambda question
« Reply #15 on: 31 July 2018, 12:17:22 »

Yep, the voltage probably dips to 9V when you start the car, so it is designed to cope with this at the very least.

Other things like the ABS and automatic gearbox will throw in the towel long before the engine ECU.




Oh well, there is no way on earth its going to drop below 9 volts so that is that theory well and truly out of the window  :y ;D
Well at least I can say it starts pretty much instantly when the key is turned now  ::) :y :y

Oh well, back to the drawing board when I get time ................. 
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Re: Lambda question
« Reply #16 on: 31 July 2018, 18:11:53 »

Are the LTFT's drifting away from 0% when on petrol?  Need to ascertain if there is a real issue, or poor LPG calibration (not that the Stag allows good LPG calibration, at best, "adequate").

That will help pinpoint :y
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Re: Lambda question
« Reply #17 on: 31 July 2018, 19:06:57 »

Are the LTFT's drifting away from 0% when on petrol?  Need to ascertain if there is a real issue, or poor LPG calibration (not that the Stag allows good LPG calibration, at best, "adequate").

That will help pinpoint :y




Long Term Fuel Trims ??


I'll stick 20 quid's worth petrol in it and drive it around for a day or so  :y

If the trims wander, how long will it take to start moving ?

The blue petrol / green lpg map lines are totally merged with no conservable gap.

Don't ask me about the other readings because even after nearly 7 years of using lpg on 2 cars, i've still not worked out what they are all about  ::)
All I can say is it runs okay  ;D
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Re: Lambda question
« Reply #18 on: 31 July 2018, 19:29:19 »

Turn off LPG for the entire timeframe of this test, to check its petrol running.

Put a fault on - say unplug maf and drive it a few hundred yards. Plug it back in, then clear all engine codes (if there is a code stored, this usually resets all the BLMs, including trims).  So at least they start at 0% ;)

Then drive around (on petrol) for a couple of days (50 miles or so, or whatever), then check both LTFTs again.

If they have both drifted from 0%, then you have a problem, unrelated to LPG.  If they both drift similar amounts in same direction, look for airleaks, else suspect the MAF (2.6/3.2 MAFs do tend to degrade, unlike the more reliable 2.5/3.0 that go on forever, then die completely). If one drifts and the other doesn't much, suspect air leaks or sensor.
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Re: Lambda question
« Reply #19 on: 31 July 2018, 22:28:43 »

Turn off LPG for the entire timeframe of this test, to check its petrol running.

Put a fault on - say unplug maf and drive it a few hundred yards. Plug it back in, then clear all engine codes (if there is a code stored, this usually resets all the BLMs, including trims).  So at least they start at 0% ;)

Then drive around (on petrol) for a couple of days (50 miles or so, or whatever), then check both LTFTs again.

If they have both drifted from 0%, then you have a problem, unrelated to LPG.  If they both drift similar amounts in same direction, look for airleaks, else suspect the MAF (2.6/3.2 MAFs do tend to degrade, unlike the more reliable 2.5/3.0 that go on forever, then die completely). If one drifts and the other doesn't much, suspect air leaks or sensor.




Brilliant  :y
Thanks TB  :)
I'll do that in morning and report back in a couple of days with my findings   :y
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Re: Lambda question
« Reply #20 on: 01 August 2018, 16:23:40 »

Given how they are little more than a modifier applied to the petrol injector timings, they could be merged on drifted block learn values...hence the reset the learns and run on petrol then re-merge the LPG



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Re: Lambda question
« Reply #21 on: 01 August 2018, 17:45:22 »

Given how they are little more than a modifier applied to the petrol injector timings, they could be merged on drifted block learn values...hence the reset the learns and run on petrol then re-merge the LPG

Yes, if it's actually being used on LPG, then it only collects data on petrol running when cold and mostly open-loop, so, before making any judgements, it's worth clearing the fuel trims, clearing the collected data in the LPG ECU and collecting fresh data on both petrol and (after that) LPG.
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Re: Lambda question
« Reply #22 on: 02 August 2018, 10:11:46 »

Given how they are little more than a modifier applied to the petrol injector timings, they could be merged on drifted block learn values...hence the reset the learns and run on petrol then re-merge the LPG

Yes, if it's actually being used on LPG, then it only collects data on petrol running when cold and mostly open-loop, so, before making any judgements, it's worth clearing the fuel trims, clearing the collected data in the LPG ECU and collecting fresh data on both petrol and (after that) LPG.






Okay, so in gonad language  ;D

Un plug the MAF.
Drive around the block on petrol.
Reset any codes which should clear the short / long term trims.
Drive on petrol only for a couple of days to let the car ecu sort out its new trims.
If long term are both zero switch to lpg, wipe gas and petrol maps.
Re record petrol map for the stag ecu then re calibrate the gas side  :y


If the LT trims have both wandered, its liable to be a air leak or MAF problem.

If one sides trims are wandering, I should be looking at the lambda's on that side  :y

Apologies for more questions but i'm the sort of bloke who needs to understand what / why i'm doing something  ::)
Not just follow blindly  :)
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Re: Lambda question
« Reply #23 on: 02 August 2018, 18:11:32 »

Okay, a few pictures of the laptop screen
All driving on petrol

Checked the codes and non apparent but the LT trims was both -1.
Started the car then unplugged the MAF.
Drove it 4 miles then plugged the MAF back in and read the codes.
Codes was the Air temp and MAF but no eml for some reason  :-\
Cleared them but LT trims refused to reset  :-\

The first 4 screens are after I plugged the MAF back in and reset the codes ............. 






 




The last 2 was taken after the 4 mile drive home ..............








Anybody make sense of this lot ?
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Re: Lambda question
« Reply #24 on: 02 August 2018, 18:28:44 »

Stop oppsing around with that piece of shit, and get a usable reader ;)
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Re: Lambda question
« Reply #25 on: 02 August 2018, 20:11:50 »

That's you told...  ::)

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Re: Lambda question
« Reply #26 on: 03 August 2018, 00:15:17 »

Stop oppsing around with that piece of shit, and get a usable reader ;)


Yes boss  ;D
Pm us your card details and i'll get one ordered  :P ;D
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Re: Lambda question
« Reply #28 on: 08 August 2018, 16:40:13 »

Okay, fitted those cheapo sensors and both now switching pretty much through the full 1 volt range.
Both switching between rich and lean quickly.
After indusing a fault then clearing it, the LTFT seem to be settled on -1 after a short drive and the idle is rock solid too when warmed through.

Okay, back to the LPG side.
The Stag petrol map goes all the way back to when it had a slush box fitted.
Am I best now to totally re calibrate both the stags petrol and lpg ?
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