LPG Check Engine Code

[Djsmith7]

I have one of those pull your hair out problems. I have VY series II on LPG. The vapor pressure hose was replaced and ever since I get the Check Engine code (after being on cruise for about 1km) appearing and then disappearing after acceleration. I took to the holden dealer who said it was the O2 sensor. That was replaced, but the problem persisted. I then took it to the LPG mechanic who has overehauled the converter, changed the mixer, filter and fuel control valve. But the problem persists. Anybody got any ideas? Please!!

[O5BRKY]

Mine ocassionally after a hard acceleration does this,I reckon it could be leaning out or to rich.One of the LPG gurus should be able to help.

[mmciau]

http://www.ls1.com.au/forum/showthread.php?t=76038&highlight=LPG+VS

Have a read through this thread and in particular

vyssls1 advised that the O2 sensors have a great deal to do with the operation of the LPG component of the VS S2 Dual Fuel Acclaim I have.

I can report that YES, they sure do.

The system has been repaired and the ECM re-set to purge all the previous settings associated with the LPG configurations and the engine is now performing very nicely thank you!

[Djsmith7]

Thanks mmciau.

Yes I am aware that the right O2 sensor is associated with the LPG system. This was the first thing that was replaced. It has been back to the LPG specialist over 8 times since trying to get rid of the Check Engine warnings. Perhaps the settings in the ECM, as you suggest,need to be recalibrated or something. I will suggest it to the LPG specialist. Thanks again for your help. Does anybody else have any further ideas?

Thanks for the submit O5BRKY. Yes is is caused because the O2 sensor is recording a too rich mix. The LPG gurus are still stumped as to how to fix it. :-(

[O5BRKY]

May require a visit to Holden Dealer and get a flash update perhaps?

[vyssls1]

I have one of those pull your hair out problems. I have VY series II on LPG. The vapor pressure hose was replaced and ever since I get the Check Engine code (after being on cruise for about 1km) appearing and then disappearing after acceleration. I took to the holden dealer who said it was the O2 sensor. That was replaced, but the problem persisted. I then took it to the LPG mechanic who has overehauled the converter, changed the mixer, filter and fuel control valve. But the problem persists. Anybody got any ideas? Please!!

What type of LPG system is it running, is it a impco system, from what uve explained to me it sounds like the vehicle is trying to run in closed loope, after approx 1 km of driving, which is roughly the time it takes for the factory PCM to go through all its short and long term fuel trims, until its parameters are at the maximum limit allowed in the vehicles factory PCM tune. Also has the vehilce previously backfired, as they do damage the internals of the mixer.

If youve replaced the vapour hose, i dare say it would have been split to warrent replacing it. With this information i dare say the vehicle is now running to rich on LPG, and will require mixer adjustment, with the LPG stepper motor completly wide open. Id say the mechanic who has been working on it, hasnt really got a clue about the system he is working on, but then again neither has any of the holden dealerships in SA when it comes to a Impco LPG system.

If u get stuck give me a call.

[Djsmith7]

Thanks vyssls1.

The car has never backfired. Before (prior to last Wednesday) the check engine message displayed and as soon as some accelaration was applied (ie.cruise off because of traffic light etc.) the message would disappear. Since then the mechanic replaced the mixer (Wednesday) the message does not disappear until car is turned off or switched to petrol. Where do I look to find what system it is. On the cover on in the boot it says APA manufactoring. I believe this to be a factory fitted model if that helps.

I don't recall the mechanic saying the vapour hose had split (but it was replaced) but he did say that the diaphragm was shredded an not to use Woolworths LPG anymore. Does that help? Mechanic is from Southern Automotive Specialists. I would have thought they would know their stuff, but now I wonder. Thanks again, I may need to call you yet. Cheers!

[muzza]

If you have an Impco Gas set up with a seperate gas computer regulating your gas mixtures I would suspect your car's ECM is setting a lean fault code.
Gas is supposed to run 15.5:1 stoichiometric (air-fuel mix for lowest emissions and economy) whereas petrol is 14.7:1 stoichiometric (slightly richer) so your PCM is seeing the exhaust is too lean in fuel via the O2 sensor so setting a fault code. When you accelerate it richens up so the car's petrol ECM thinks it's OK for a little while.

Solution is to either have a switch or relay to turn off your fault light when running on LPG or see a tuner to tweak the ECM (if possible)to allow for the leaner cruise mixture and not set a fault code.

BTW I dont think Woolies LPG is any better or worse than any other brand.....

[Djsmith7]

Thanks Muzza.

I believe that the error code is that the mix is too rich. But your switch idea maybe a good fallback if it can't be sorted out.

[vyssls1]

Thanks Muzza.

I believe that the error code is that the mix is too rich. But your switch idea maybe a good fallback if it can't be sorted out.

u should never need to install a switch, so that the check engine light wont be displayed.

as for 15 AFR yes LPG does run that at stoch, but no PCM in that era, can even tell what the AFR reading is, so ur theory is incorrect.

All the PCM wants to see is the vehicle in closed loope, thats all.

How to tell if its a impco system, the LPG vapour hose is approx 1" inside diameter.

A dead give away is the solenoid to control the closed loope operation, will be a continous pulse, which actually works of a duty cycle of 60%

And the mixer will have Impco 225 from memory on that system, and all adjustments are carried outon the mixer.

As for the servo thing, thats the worst excuse ive heard coming from someone playing with LPG.

u say the diagram was shreaded, and this was the cause of woolworths LPG, well thats intersting considering its a vapour not a liquid at this point in the system.

[muzza]

Well the ECM "knows" the AFR by the O2 sensor voltage output averageing 4.5v for petrol stoichiometric of 14.7:1 and AFAIK the Impco LPG computer leans out the mix via the solenoid valve bleeding off vacuum draw on the diaphagm according to what voltage the LPG computer reads off the O2 sensor. As long as the mixer is set up slightly rich the LPG computer will be able to lean it off within a range of the optimum 60% duty cycle of the solenoid valve set up.

So as the car's ECM see's it, the O2 sensor voltage is too low- lean - and so it tries to increase fuelling via the petrol injectors which no longer function, no change to the lean mix situation so the computer signals a fault it can't correct.

The vehicle goes into closed loop under conditions when engine is warm enough and throttle is below certain % - cruise and moderate accel. Problem is the LPG computer is controlling the closed loop to a leaner mix and the car ECM is still "watching" the O2 sensor.

I agree the relay to switch off the ECM fault light is bad mechanix, but if your LPG is running fine and the only fault code is rich or lean just ignore it - I used to, as it only came on in cruise conditions or heavy accel when I knew the reason was the LPG setup.

Seriously - go see a tuner who can fiddle the ECM - best solution.

[Djsmith7]

It sounds like you guys know your stuff. I wish had found this forum months ago. This has been bugging me for over 3 months and now I just want it fixed so I can sell it. I don't feel right about selling it with these error messages. Can you suggest anyone in Adelaide that has the expertise to fix/tune it? I am at Alberton. Cheers

[Dr.Gas]

The factory VYII uses the PCM to control a fuel control valve running at between 0 and 99 duty cycles. 30 to 50 is ideal. One other thing to check is the RCV or dump valve on the front of the converter. The RCV is a normally closed valve that is supposed to 'crack' open on hard acceleration. If the RCV gets stuck open an atmospheric bleed is introduced. This renders the fuel control valve inoperative as the air valve vacuum applied to the top of the diaphram simply bleeds out through the RCV without contolling the fuel mixture. A rich code is then logged. Maybe worth a look.Also the 225 mixer on the factory system usually has 'tamper proof plugs' to stop adjustment of the idle and WOT settings a pain in the date but an emission addition.

[Djsmith7]

For those interested the problem seems to be resolved. Almost 4 weeks and no error messages. Various things have been done. Lever height of the converter was modified, replaced mixer and converter. In the end a different air filter was installed and that seems to have done the trick. Thanks for everyones help.

[Dillzio]

I have one of those pull your hair out problems. I have VY series II on LPG. The vapor pressure hose was replaced and ever since I get the Check Engine code (after being on cruise for about 1km) appearing and then disappearing after acceleration. I took to the holden dealer who said it was the O2 sensor. That was replaced, but the problem persisted. I then took it to the LPG mechanic who has overehauled the converter, changed the mixer, filter and fuel control valve. But the problem persists. Anybody got any ideas? Please!!

On my VQ 5L, the engine light came on sometimes on gas and would flash code 44 or 45, which means the exhaust 02 sensor voltage was detecting it as too rich or too lean. I put it down to the fact that when you're on LPG, since the fuel injectors aren't operating the ECU has no means of controlling the fuel delivery to keep the air/fuel ratio right so it goes too rich or lean sometimes.