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High negative LTFTs on Subaru Tribeca
http://lpgforum.co.uk/viewtopic.php?f=28&t=14212
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Author:  Brian_H [ Thu Aug 31, 2017 9:49 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

For the price of a bottle of ic12 i'd give it a try as a first step - I've known it to improve problematic injectors previously, If they are gummed up with lube that might be enough to clear them (couple of applications on each rail). Though to be fair i'd have expected your specialist to have sorted that out with the leaked lube fix etc. I'd certainly give the cleaner a go before touching the software settings if you now have the access to them. It might be worth posting some screenshots of the settings if you have the software though?

Author:  DJB1 [ Thu Aug 31, 2017 10:52 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

No haven't got software or cable yet. The worsening features suggest a mechanical fault rather than software. Yet again, I'm getting the occasional P0420 error code (cat below efficiency) which has previously signified internal destruction of one or other cats. I think that when I accelerate hard (which I like to do), the ECU switches to open loop and major over fuelling is occurring. Either that or the non oem sports cats are not up to the job.

Author:  Brian_H [ Thu Aug 31, 2017 10:57 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

DJB1 wrote:
No haven't got software or cable yet. The worsening features suggest a mechanical fault rather than software. Yet again, I'm getting the occasional P0420 error code (cat below efficiency) which has previously signified internal destruction of one or other cats. I think that when I accelerate hard (which I like to do), the ECU switches to open loop and major over fuelling is occurring. Either that or the non oem sports cats are not up to the job.


Simon can confirm, but it may be possible to switch cylinders between fuels - this can isolate the fault to a bank etc. (newer AEB ecus allow this, not sure with BRC)

Could equally be the calibration is off - either its wired with banks crossed over, or its running with a combination of nozzle size/pressure that just won't work as Simon pointed towards above. Depends if its ever worked with the settings you currently have? Though no amount of calibration will correct dodgy injectors perfectly.

Author:  LPGC [ Fri Sep 01, 2017 8:54 am ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

BRC Plug n drive does allow switching individual cylinders between fuels and it's a check worth doing. For conclusive per injector comparisons it's necessary to do it at idle and under load while closed loop.

The standard cats are reliable, if the fitted cats are 'sports none OEM', how do we know they're reliable and wouldn't break in the same time period running on petrol as running on LPG anyway?

Summing possible LPG causes up we're looking at lube flow, lube gumming/damaging injector(s), poor injector/pressure combination, poor calibration at high loads.
Other issues can cause the same effect too, such as crimped injector to manifold pipe(s) - This would make effected cylinders run leaner than others particularly under load, lambda will reflect around the average mixture on each bank so if some cylinders are leaner than others on a bank it implies some cylinders will be richer. Not all gas in a rich cylinder will be burned, the remaining gas (particularly in conjunction with the remaining air from the lean burning cylinder) can then overheat the cat.

Something must be wrong with the lube system or mixture if the cylinder heads are suffering vsr.

Simon

Author:  DJB1 [ Fri Sep 01, 2017 5:22 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Thanks Brian_H and Simon

The VSR issue may have been due to the lube being inoperative for a while (broken wire to float switch) or because lube was plumbed in upstream of filter. Both were addressed some time ago. I don't know whether the sports cats are reliable but I was assured by fitter that he has fitted this type to hundreds of cars most of which are high performance and very few have had problems. I suppose that he might be lying but he seemed trustworthy and has replaced burnt out ones at cost price.

If lube blockage of injectors is an issue then I'm sure that I will have it having now done about 100000 miles on LPG. I'm not willing to spend much money on this car. I've had my money's worth but it's a good work horse and apart from the 20 mpg on petrol, it's not that expensive to run now that I do all the maintenance myself.

Author:  rich r [ Sun Sep 03, 2017 9:14 am ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Don't forget that the EZ30D engine is prone to a little VSR over 100,000 miles even when run purely on petrol, so unlubricated LPG will definitely accelerate what would already be going on.

The standard cats on the Legacy/Outback/Tribeca 3.0s are indeed generally reliable until well over 200,000 miles - there are some reports on the Australian Legacy (Liberty) forums of the original cats and exhaust system still being perfectly fine after 600,000km (375,000 miles). That is of course assuming that the engine is running within acceptable a/f ratios on all six cylinders. There have been reports of certain types of sports cat fitted in the front cat positions failing and being sucked back into the cylinders, especially with better flowing headers.

Author:  DJB1 [ Fri Dec 08, 2017 4:32 am ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

I’m now working abroad so don’t have any time to tinker with the engine. The IC12 cleaner made no difference. I’m fairly certain now that the injectors are clogged or damaged. I’m now thinking that a quick fix (if there is one) would to replace injectors (either new which will be around £250 for 6) or used (for £80). Given the current issue, I would favour getting the new ones. I appreciate that the purists here will tell me that everything will need to be recalibrated, etc but I just don’t have the time now (I’m back in UK for about 4 weeks per year). I need to use the car when I’m back and my wife uses occasionally in bad weather or if she needs a bigger car. I figure that there’s not much to lose (ok £250) but if it resolves the problem, I’ll be delighted.

Is this unwise?

Ps I’m assuming that the old injectors cannot be cleaned (ultrasonic cleaning available for petrol injectors but they need to be sent away)?

Author:  LPGC [ Fri Dec 08, 2017 4:42 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

I've just read the full thread again, needed to recap!

So far we've talked fuel trims but it hasn't been mentioned if trims are the same on both banks of cylinders... If they are the same on both banks it could point a bit toward it being a calibration issue, or if trims are very different cross banks it could point to it being an injector issue, not conclusive in either case though.

The point about BRC 'through injector' lube systems causing injector problems has been raised, I don't think it's been confirmed that the lube system is the through injector type but it does seem to be considering the reservoir has a float and injector pipes seem oiled up. Through injector type lubes can cause injector problems that couldn't be cured using cleaning fluids - that might seem a bit counter-intuitive since we'd expect just to be able to flush out any gummed lube oil, but I have found this to be the case on many occasions, in fact I find that most BRC injectors that fail prematurely failed because they were used in conjunction with a through injector lube system. I wouldn't expect ultrasonic cleaning to fix injectors that injector cleaning solution didn't fix.

The problem with buying second hand injectors of course is that you don't know they will be in a different condition to your injectors. If you do buy second hand I'd only advise buying them if they came from a vehicle that didn't have a through injector type lube system fitted.

Simon

Author:  DJB1 [ Fri Dec 08, 2017 10:04 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Simon

Trims similar on both sides and through injector lube system (for nearly 100 000 miles). If gumming up of injectors is common with this set up, then I’ll have it. So it sounds like a new set of injectors. I wish I had the time to bring it down to your garage and I know that you would fix it properly but I just don’t I’m afraid. I’m working overseas and back for 2 weeks for the first time in 3 months.

Thanks for helpful advice.

Author:  LPGC [ Sat Dec 09, 2017 10:59 am ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

No probs you're welcome :-)

Simon

Author:  DJB1 [ Wed Jan 10, 2018 8:06 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Was back in UK for 2 weeks over Christmas and found some time to replace injectors with second hand ones that I got on eBay (£80 for 6 including the two rails). Had to swap over rails due to different sensor connector on eBay one. The injectors were same as old ones. Odd behaviour on first switch over. LED lpg fuel gauge behaving very odd - sometimes very dim or no lights at all, sometimes normal. I double checked that all the connectors were fully pushed home and this particular issue seems to have gone away and LPG running very well.

Anyway, I think Simon was absolutely right. Trims are not perfect and for reasons that I can't work out, bank 1 is now running lean (corrected by positives trims especially at idle) and bank 2 slightly rich (negative trims at idle). But the one thing that I wanted, the trims on petrol and LPG are almost exactly the same.

You might suggest a vacuum leak on bank 1 side but revving the engine to 2500 rpm makes little difference to negative trims. They do however trend towards zero on mid/full throttle on load (both bank 1 and 2). I've also got some odd chassis related error codes (C codes). They preceded injector swap so probably not related. The codes (not regular P codes which are clear) seem to be related to the traction control or braking system but I am unable to find model specific info. I'll look into this next time I'm back in UK.

Author:  rich r [ Fri Jan 12, 2018 7:07 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Not related to your engine isues of course, but if you post the C codes, I can see what they relate to in the Subaru workshop manual for the Gen IV Legacy/Outback, which the Tribeca is sort of based on. Most likely it's just historic dirty ABS sensors or a low battery (which can cause all sorts of fault codes relating to communication issues because the body control module powers up after some of the other modules, and so misses their initial data transmission).

Author:  LPGC [ Sun Jan 14, 2018 12:03 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Hi Rich, Thanks for the recent recommendation, Outback conversion booked in for Jan 22nd.
Cheers, Simon.

Author:  LPGC [ Sun Jan 14, 2018 12:11 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

DJB1, pleased your problems seem to have been cured.
The switch sometimes going dim could still be of concern, could point to the ECU getting low voltage. You were right to check battery connections, I'd also advise disconnecting the ECU and checking for burned/tarnished/corroded pins on the ECU's connector... I've sorted quite a few BRC systems just by cleaning ECU's connecting pins up.

Simon

Author:  DJB1 [ Tue Jan 16, 2018 1:13 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

rich r

Codes are:

C0281
C0261
C0262

I also have 'Err SS' on tripmeter which I believe stands for speed sensor. The ABS and traction control warning lights are on most of the time (but I have also seen them go out). Sometimes I see the brake warning light on as well but this is less common. I'm suspecting a wheel bearing or an ABS related issue.

D.

Author:  DJB1 [ Tue Jan 16, 2018 1:16 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Thanks Simon - will check next time.

Author:  rich r [ Fri Jan 19, 2018 10:49 am ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Sadly those C-codes aren't listed in the Gen IV Legacy/Outback service manual (highest code I've got is C0140). I suspect then that the Tribeca being that bit newer has a different transmission control system, or the Legacy one doesn't quite fit with the different chassis - even though the engines, gearboxes and most of the dashboard etc are the same.

However ErrSS does indeed indicate that the instrument panel isn't getting a reliable speed signal. It might be a fault with the sensor, or it might be a canbus fault. If you don't have P0500 then I would suspect it's not the main sensor itself. Might be worth asking on the Tribeca Owner's forums eg www.sb9t.com.

Author:  DJB1 [ Fri Jan 19, 2018 6:15 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

rich r

The speedometer is not working now so something really odd going on. I'm still overseas so I've asked my son to read the chassis codes which you can do with a sequence of tripmeter button pressing and switching headlights on and off. I have the Tribeca FSM but it also doesn't have these codes which seems strange. I suppose an electrical fault is high up on the list given the dim or absent lpg fuel level lights a few weeks ago although I'm told that that issue has been ok. ABS speed sensor failure is not unusual so is another possibility. Sometimes this is associated with a worn wheel bearing.

Author:  DJB1 [ Fri Jan 19, 2018 6:19 pm ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

Oh another thing: the battery has gone flat a few times in the last 6 months and I plan to replace. The v belt tensioner needs to be replaced which might be related.

Author:  4eyes [ Sat Jan 20, 2018 8:06 am ]
Post subject:  Re: High negative LTFTs on Subaru Tribeca

C0281 is to do with the electronic parking brake I think? Mine was disabled on my 2011 outback when my battery crapped itself 12 months ago. Can't find any reference to the other codes, but like others have said, a dodgy battery is known to throw random codes on Subarus.

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