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[arthill]

 
[/quote]
Believe it or not we have the same car at work with the same faults, code 0340 and 0170 fuel trim. The fuel trim is probably the O2 ( lambda ) sensor either pre or post cat. If you have changed the cam sensor then next step is to check the tension of the cam belt, if it is incorrect the cams can move ever so slightly and get an incorrect signal. The last 2.2 facelift we had we gave up on and sent it to auction as the ecu was sh----d. Our work car does exactly the same and sometimes the MIL does not come on at all and the car runs fine.[/quote]


Has anything been tried that I haven't mentioned in this thread, please let me know if you find out cause

  John

[arthill]

Hi
  as I reported in previous thread, I still have fuel trim fault, lean I'm sure mechanic said
he reckons this could be giving fluctuating readings from one of the lambada sensors, although this is not showing up as a fault on readings, could this be as he suspects something to do with MAF sensor. Any Ideas  :-?

  John

[The Cambelt Kid]

Hi
  as I reported in previous thread, I still have fuel trim fault, lean I'm sure mechanic said
he reckons this could be giving fluctuating readings from one of the lambada sensors, although this is not showing up as a fault on readings, could this be as he suspects something to do with MAF sensor. Any Ideas  :-?

  John

I had same errors on my LPG'd MV6 and it would only occur when running on gas.  

0170 - Fuel Trim Mafunction (Bank1)
0173 - Fuel Trim Mafunction (Bank2)

Turned out to be the LPG injector nozzles being too small and were restricting the gas flow at high revs.  I drilled these out and the errors vanished!

Obviously drilling out the nozzles is nothing to do with your problem, however it is related to fuel/air mix and/or lambda.  It is possible to monitor the voltage on the lambda with a scope/ analogue meter, so if you feel confident you could try and diagnose the problem that way.  I don't know a great deal about lambda's, but as far as i am aware the voltage should hang about 0.9-1.1 volts and if it drops below or above this band the car is running lean or rich, or the other way round??

My LPG nozzles were too small, so it mush have been running lean at high revs?  I didn't measure the lambdas as i had only just installed LPG and had a good idea of the cause.  If drilling the nozzles out had not fixed the problem i would have measured the lambdas to diagnose.

Also i'm sure MAF show errors whereas Lambda's dont - Can anyone back me up on this?  

[Kevin Wood]

Lambda sensors give an output in the range of 0 - 1 volt on the whole.

Generally voltages below about 0.5 volts indicate lean of an ideal mixture and those above 0.5 volts indicate rich. The ECU controls the mixture by making small adjustments around the ideal mixture and watching the Lambda sensor output. If you put a scope or a voltmeter on the lines you will see them flicking between gretaer than 0.5 volts and less than 0.5 volts every couple of seconds or so, maybe faster, as the ECU makes its' adjustments. The ECU will only do this under certain conditions. The engine needs to be fully warmed up for a start and some systems don't do it at idle so the engine revs may need to be raised to 2,000 RPM or so.

What this fault seems to indicate is that the corrections made have gone outside the allowed range. If you can find the exact codes reported that would be a good help.

Edited to say: It may well be that if the sequential operation of the injectors has been impaired by the cam sensor problem the ECU has "learnt" a different fuelling strategy to compensate, so put a few miles on it before doing anything else and see if the fault clears.

Kevin

[magnul]

I guess that the car in question is OBD2 compliant? If so a long term fuel trim>25% is required to throw up a fault code. Such a high long term fuel trim is probably due to insufficient fuel pressure or partially clogged injectors.

[The Cambelt Kid]

Lambda sensors give an output in the range of 0 - 1 volt on the whole.

Generally voltages below about 0.5 volts indicate lean of an ideal mixture and those above 0.5 volts indicate rich. The ECU controls the mixture by making small adjustments around the ideal mixture and watching the Lambda sensor output. If you put a scope or a voltmeter on the lines you will see them flicking between gretaer than 0.5 volts and less than 0.5 volts every couple of seconds or so, maybe faster, as the ECU makes its' adjustments. The ECU will only do this under certain conditions. The engine needs to be fully warmed up for a start and some systems don't do it at idle so the engine revs may need to be raised to 2,000 RPM or so.

What this fault seems to indicate is that the corrections made have gone outside the allowed range. If you can find the exact codes reported that would be a good help.

Edited to say: It may well be that if the sequential operation of the injectors has been impaired by the cam sensor problem the ECU has "learnt" a different fuelling strategy to compensate, so put a few miles on it before doing anything else and see if the fault clears.

Kevin

Well said Kevin!  I knew i wasn't too far out.... you seem to explain things much better on the screen too.

Cheers
M

[arthill]

Lambda sensors give an output in the range of 0 - 1 volt on the whole.

Generally voltages below about 0.5 volts indicate lean of an ideal mixture and those above 0.5 volts indicate rich. The ECU controls the mixture by making small adjustments around the ideal mixture and watching the Lambda sensor output. If you put a scope or a voltmeter on the lines you will see them flicking between gretaer than 0.5 volts and less than 0.5 volts every couple of seconds or so, maybe faster, as the ECU makes its' adjustments. The ECU will only do this under certain conditions. The engine needs to be fully warmed up for a start and some systems don't do it at idle so the engine revs may need to be raised to 2,000 RPM or so.

What this fault seems to indicate is that the corrections made have gone outside the allowed range. If you can find the exact codes reported that would be a good help.

Edited to say: It may well be that if the sequential operation of the injectors has been impaired by the cam sensor problem the ECU has "learnt" a different fuelling strategy to compensate, so put a few miles on it before doing anything else and see if the fault clears.

Kevin

Thanks for response to my problem, Kevin said to put some miles on car for new values to be learnt, already done approx. 200 miles, how many more should this take normally before next adventure. Will get back tommorrow with code.

thanks again John

[arthill]

Hi

 Got fault code today P0170 only code shown , come a long way with this car would appreciate any help to sort it completely

  John  :-/

[arthill]

p0170 can anyone tell me usual causes. Fuel trim lean


 John

      

[TheBoy]

p0170 can anyone tell me usual causes. Fuel trim lean


 John

      

Difficult to tell without seeing a live data, but would be guessing maybe an issue related to lamdas.

Was the code reader via Tech2 or generic reader, as if the latter, that may be wrong description (many P codes are the same but with different text, and generic readers cannot deal with this too well)

[arthill]

Mechanic took live reading of lamba sensors said one was fluctuating which he wouldn't expect to see, not sure if it was before or after cat. suspects unspent fuel as possible cause, but lamba sensor fault not shown up only P0170 fuel trim.

  John

[TheBoy]

Mechanic took live reading of lamba sensors said one was fluctuating which he wouldn't expect to see, not sure if it was before or after cat. suspects unspent fuel as possible cause, but lamba sensor fault not shown up only P0170 fuel trim.

  John

I'd expect the pre cat one to flick between rich and lean, and the post cat to read lean....