Cleaning fuel injectors for lean bank 2

[Jiranimothe1]

Hello, looking for advice on Subaru Legacy 2004 EZ30 engine with LPG conversion as Im battening a lean bank 2 code with cylinder 1,3,5 misfire and extremely low rpm.

The history so far, I’ve change spark plugs and coil pack, cleaned the MAF, filled in a hole in the exhaust and replaced air chamber leak, checked the o2 sensors, replaced PCV valve and cleaned the throttle. Done a smoke test trying to find another air leak and didn’t. The CEL and code however is still persistent and doesn’t go away. Not sure what to do next really.

On a note I’ve noticed recently that when I put petrol in after only having a quarter, the CEL was gone, but low rpm and rough idling stayed.

So my theory is That the issue issue is with the fuel injectors who make the mixture too lean (dirty or clogged up) and since as far as I understand the LPG ecu uses the petrol ECU as a base line, this also extends to LPG performance.

Is my theory correct?

If so, can I use injector cleaner like Chevron Techron Concentrate Plus for petrol to clean the petrol injectors? Or will I damage the engine as it has LPG?

Sorry for the long thread…

Thanks,
Eli

[Brian_H]

It won't do any harm to the lpg system, as it won't get anywhere near it (provided you put it into the petrol tank of course which I think is what your intending).

Is its doing it on both fuels? (you might need to run it on petrol for a few miles to tell for sure to let it relearn the correct trims)
Can you access fuel trim data to see whats going on? (you obviously have access to the fault codes, but the trims will give a better picture of whats happening)

Any idea what lpg system is fitted? Do you have a lead and software for it?
Does it have any sort of valve saver system fitted? Possibily consider doing a compression test if you have the tools to do so?

[Jiranimothe1]

My reader doesn’t show fuel trims. It’s very basic. But I’ll order a more advanced one see what it says. What sort of trims should it show on petrol?

I have no idea as to which LPG system is fitted, there is no valve saver system / flash lube fitted (when I got the car I didn’t know any of that was necessary). Nor do I have a software lead or a compression test kit.

I hoped it would be a simple air leak since I spotted 2 and fixed them already. How long do I have to run it on petrol usually for the relearn? As I tried the Subaru idle relearn but it’s done nothing. As in I’m not even sure it learns anything.

[Brian_H]

I'd expect a drive of around 10 miles should be enough to get it to relearn. But that would be with functioning sensors and no faults present. Much easier to confirm sensors are working if you can see live data (fault codes aren't always logged).

It may be worth unplugging the maf and seeing if it runs any better like that. Worth being aware there will be a vacuum line from the lpg vapouriser to the inlet manifold, and may be worthwhile to either give that a good check over, or temporally block it at the manifold to see if the fault lies there. You smoke test should pick that up with any luck anyway, but its an easy thing to check before you buy anything.

It would be a good idea to identify the system if you can - photos of the bits you can find will help there, the main thing to identify will be the vapouriser, injectors and ecu in use.

[Brian_H]

Also I think but not 100% sure that you would need a valve saver system. Trims wise you want to see somewhere around the 0 level. If one bank is stuck at 25% theres clearly an issue there, what would be useful to see is if it stays the same on both banks and both fuels. Should be able to rule out the MAF if the other bank looks ok. Cheapest option for a code reader with live data can be a bluetooth dongle and a phone app like torque, but not sure that Subaru will speak to that. Others on here have recommended the Launch c reader as it will do jobd which is needed for some Japanese cars.

[Jiranimothe1]

Awesome thank you Brian. I order a good reader to see the trims and 02 sensors voltages. I’ll have to try and figure out what is part of the LPG system as well (I guess anything that Is alien to a regular petrol set up). Also is it safe to disconnect the MAF while the engine is running or even run the engine without a MAF?

[Brian_H]

Worst your likely to get with the battery disconnected is that it cuts out. Best to leave it in place as otherwise you have the intake open to atmosphere without the air filter doing its job.

[LPGC]

If an engine misfires then besides OBD codes for misfires it is also likely to have OBD codes for lean mixture, because when a cylinder misfires it pumps air into the exhaust.

You have recently worked on the exhaust system? If a lambda probe is broken/damaged it may signal lean mixture when mixture is actually rich. In this state it may run rough on petrol but not misfire, while on LPG it may misfire.

How did you check lambda probe function with the engine running rough or misfiring? On most Subaru H6 engines the front probes are wide band.