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[tigers_gonads]

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 

[Marks DTM Calib]

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

But yes, its the front two 

[tigers_gonads]

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

But yes, its the front two 

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  , 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 


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

[Doctor Gollum]

Has the lpg been recalibrated recently?

[tigers_gonads]

Has the lpg been recalibrated recently?

Yup 
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 


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     

[Doctor Gollum]

You could try a 140 amp alternator...

Follow Kevins starting/charging test and go from there

[tigers_gonads]

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

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 

[Doctor Gollum]

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

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 

And you're a Sparky

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

[tigers_gonads]

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

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 

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 

[Kevin Wood]

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.

[Kevin Wood]

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.

[tigers_gonads]

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   

[Nick W]

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.

[aaronjb]

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 ).. 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!

[Kevin Wood]

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.