Engine Management Zafira question

[lisbon_road]

We have a Z18XE Zafira A automatic with BRC LPG system.  It isn't happy on lpg but need to get it right on petrol first.  It can come up with P0170 (2) lean exhaust and seems to have the following:

 

Long term fuel trim is about 15%.  Short term fuel trim increases as power comes on.

 

First lambda signal looks fine, and sensor is nearly new.  

 

Second starts out, once warm, ok at about 0.4-0.45 volts then drops right off to settle at about 0.1 volts or even less.  Can see that if I use Op-com to log data.

 

 

What's going on then?  Is 15% LTFT enough to be concerned about (I'm thinking it is)?  This is presumably not an air leak as it is more when under power when vacuum is less.  Could it be dirty MAF?  The MAF isn't very old and is a decent one.  I'm a bit apprehensive of cleaning the MAF as it looks very fragile.  

 

Does it sound like the second lambda is knackered?  Can I put an old front lambda in to try it?  I'm thinking that this is unlikely to be an air leak as it gets worse, so do lambdas do that?

 

It just passed its MOT with emissions of CO zero and Hydrocarbons 8 ppm.  

 

Any help appreciated.  I'm learning fast though a way to go yet.  

 

And why doesn't Op-com seem to read LTFT?  Perhaps I am missing something.

 

 

 

[twosmoke300]

If fuel trim gets worse under load then its usually MAF - if it climbs on idle then its a leak somewhere.

Try cleaning the maf first but a quality replacement is the way to go. Not lucas or chinky ebay specials

[lisbon_road]

Thanks.

 

It was a quality replacement about a year or so ago, Siemens or Bosch I think, not as you say a Chinese Europarts one.  Cost a fair bit too.

 

I'll try cleaning it.  Seem to be plenty of stuff on youtube about how to clean them.

 

Incidentally, I know you're not supposed to just go out and buy stuff to trial and error fix as it gets too expensive but I think it is worth having a pile of secondhand bits for a car as cheap as this, to help with fault finding.  I recently bought a lambda and a coil pack (for a different story) secondhand and they charged almost nothing for them providing I didn't want a guarantee.

 

If anyone knowledgeable wants to comment on whether that second lambda is dead, that'd be welcome thanks.  Tempting to just put a 0.45 volt signal in and see if that fixes the P0170.  Not sure if I have one fault or two here.

[Split_Pin]

No signal from the after cat sensor will fire the emissions light. Is that illuminated?

[Stanky]

L-R

 

I've got a Delphi DS150e which I think has a wider range of diagnostics than the Op-Com that you let me borrow a couple of years back. Give me a shout if you want me to pop over with the cable and laptop and we can have a go at finding out more info on it.

[scaryoldcortina]

I agree with twosmoke about it being the MAF, second lambda sounds like it's working normally - it's after the cat so once warm will always signal lean if the cat is healthy.

[lisbon_road]

The second lambda should give 0.45 volts or so to represent an ideal mix.  It can't show lean all the time as there should not be enough oxygen.

 

Yes, it can bring on code P0170 (2) lean exhaust, but I'm not convinced it is right.  That second lambda almost can't be right.  Presumably an air leak could make it but why does it start out ok then drift down?

[UltraWomble]

We have a Z18XE Zafira

 

Perhaps I am missing something.

The scrap man.

 

We had one - something like 23 breakdowns in 18 months of ownership for a 1 year old car. Shit personified.

[red5]

More than one a month for 18 months? And you kept it for 18? Blimey,its not a Frontera

 

Check MAF barometric pressure reading - 100 kpa approx. Often overlooked.

[UltraWomble]

More than one a month for 18 months? And you kept it for 18? Blimey,its not a Frontera

 

Check MAF barometric pressure reading - 100 kpa approx. Often overlooked.

There were LOTS of arguments with Vauxhall & the dealer on that score - but yes - all the FTP / Limp Wrist Mode were to do with the DPF of fecking doom and the EGR of grief. I think the record was having the DPF forced regen & resetting the fault codes three times in two weeks, after that we had a new DPF and exhaust.

[lisbon_road]

I dunno what a MAF Barometric pressure reading is.  Well, I understand the words, sounds a bit like a MAP sensor too, so more to get my head round.

 

This car is petrol/lpg so no dpf and, as far as I can see, no egr.  It certainly hasn't been trouble free, but I can't blame it for the accident or the after market water pump someone fitted which came in half.  And it goes ok once running, in a blancmonge pudding sort of way.  If you know what I mean.

[lisbon_road]

I googled it.  I think that MAF barometric pressure is a diesel thing.

[Split_Pin]

No EGR on the Z18.

 

Ive had my Astra with a Z18 for nearly 13 years and its been relatively trouble free.

[twosmoke300]

The ecu reads the atmospheric pressure either via dedicated sensor or the ecu itself. It used this to determine altitude .

Can’t remember the exact engine code but are the two breather pipes clear where they join the throttle body - the older ecotec had a pin hole that used to block and cause fuel trim and idle issues

[red5]

The ecu reads the atmospheric pressure either via dedicated sensor or the ecu itself. It used this to determine altitude .

Can’t remember the exact engine code but are the two breather pipes clear where they join the throttle body - the older ecotec had a pin hole that used to block and cause fuel trim and idle issues

 

 X variants iirc. I'll see if I can fire TIS up. Can't remember if it's actually in the ecu on the Z18. It's a long time ago.....

[lisbon_road]

A while back, I cleaned out the smaller of the two breathers.  It is very small, wasn't easy to clean but I got it done.  I can easily check it again, so will do so.  The other bigger one was clean.  

 

Because STFT does down as pull away, and vacuum will therefore reduce, I don't think this is an air leak but I will try it.  

 

Frankly, biggest problem with this stuff is actually getting the car: my wife gets home at 9pm in the evenings after work and weekends fill up.  Not the only one who has this I guess.

[lisbon_road]

It was the MAF.  Replaced with a Delphi one and the Long Term Fuel trim dropped off, the short term fuel trim hovers around zero, the second lambda signal is now sensible and it runs fine on LPG without that system being touched.

 

Bit expensive, but we got there. 

[twosmoke300]

Result ! It hasn’t got a k&n type air filter has it ? The oil from those can kill a maf really quick . Be worth checking whatever filter it has for correct fitment and cleanness too . Mafs usually fail for a reason

[lisbon_road]

No special air filter and it is changed regularly. No leaks and the throttle body stays clean so I don't know why it has failed. I did try cleaning it very carefully..But... I can now clean it brutally as it is scrap.

 

Thanks for commenting.

[twosmoke300]

A quick squirt with some brake cleaner usually helps them

[Stanky]

Well done on that L_R - glad it got sorted out. Was the MAF better or worse than the £400 needed to buy a genuine Siemens one for a Mk1.5 Kia Rio? We sold it rather than swallow that cost!

[lisbon_road]

I tried the brake cleaner.  I might try it again on the one I've taken off - or a good scrub with washing up liquid given that it's no good otherwise.

 

£80 from ECP with their usual daft offers.