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Discussion Starter #1
Hi all,

I've got a 2000 4.6 HSE which has an sequential lpg kit mounted on 05/08.
Until this summer, I can nicely switch between lpg and petrol without having any serious performance difference. But especially for one or two months, it can't run well after 2000-2500 rpm on petrol. I got an AEM Dryflow filter and an AEM Wideband AFR apart from stock. First the wideband came, then the filter. Especially after the filter, when I switch to petrol, it reads zero at the afr when reachs 2500 rpm, just like cutting fueling.
I can't tell this was started with lpg conversion. Because; apart from air-fuel ratio reading, it falls nearly 200-400 rpms down when this occurs. And this started nearly 1 month ago.
Now I need your opinions for solving this problem. For assistance;
- I tried disconnecting maf(which is cleared well by brake cleaner with the new cone filter), but nothing changed.
- I don't think it's a fuel pump issue. Because it's just a little leaner until 2500 rpm, it reads 14-16 at cruise/idle.
- O2 sensors changed twice, last one is a Bosch universal 4 wire sensor. Sometimes they tend to be seem lazy at OBD, but I can easily see the rapid switching from the afr gauge.
- I had an adaptive vaules reset several weeks ago for this. I made 400-500km with only using petrol, then had lpg recalibrated. Nothing changed, 11-12 even 10 at full throttle with lpg, switch to petrol than game over, way too lean.

I hope somebody can help me with this.

Cheers,
Can
 

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Discussion Starter #2
And also;
After the adaptive values reset, it runs like a dream on petrol, for 400-500km exactly. But when I start to drive on lpg, fuel terms get f****d up :/
I wonder If I don't make enough kilometers after resetting the values?
This is the shortage of the first message.
 

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Mine was running rough and would occasionaly stall on the first attempt of starting and also suffered massive flat spots on petrol. I was told my LPG system just needed tweaking as the mixture of the LPG from filling stations is changed with the seasons and the new mix didn't sit very well with the preset settings on my system.

Not sure how much truth there is in that :? but thats what the people who installed it said and after some breif tweaking it was running fine again with little difference betwean gas and petrol. I was told it happens from time to time and it will probably need tweaking every 6 months for the best performance due to the change in fuel mixture.
 

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Discussion Starter #4
If I got it right, the o2 sensors must not log or something when on lpg in order to keep petrol fuel trims well. But this can be done whether by bypassing o2 sensors at lpg switchover (but this effects sequential lpg systems which takes signals from ecu and injectors) or by a standalone ecu.
There must be a mistake, this can't be so messy like this.
 

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11001001 said:
If I got it right, the o2 sensors must not log or something when on lpg in order to keep petrol fuel trims well. But this can be done whether by bypassing o2 sensors at lpg switchover (but this effects sequential lpg systems which takes signals from ecu and injectors) or by a standalone ecu.
There must be a mistake, this can't be so messy like this.
You haven't said what make and model of lpg system do you have - might help. Also who installed it and has it had any subsequent work done on it that may have meant the wiring or lpg fuel pipes to the lpg injectors being disconnected and reconnected?

A full sequential lpg kit does not bypass the O2 sensors - it piggy backs off the cars own ECU and fuelling calculations. If the lpg system is set up correctly the fuel trims will not be effected when you run lpg, if they are then there is a problem with the lpg system or it's calibration.

You mentioned in the 1st post you have fitted wideband AFR - not sure what this is - are you referring to a wideband O2 sensor? If you are did you replace the original O2 sensors with the wideband one or with the after market universal ones you mention. I have found from personal experience the universal ones did not work correctly and I'm sure the wideband type won't work with the car's ECU. When it comes to either MAF or O2 sesnors stick to genuine they are the only ones that work correctly.

If you have access to OBD reader, which from your post I think you have, drive the car on petrol at steady speed and throttle position - note short term fuel trims. Then drive exactly the same on lpg - the fuel trims should be very close - the closer the better. If they are not then the lpg system is not set correctly. Repeat this for different combinations of load/speed/throttle.
Have you got the software and interface lead for the lpg system? If so adjust the calibration at each point until you do not see any change in fuel trims.
 

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Discussion Starter #6
@AMcK;

It's a full sequantial Teleflex GFI kit. It has been installed by the engineer and his crew who runs the Teleflex GFI Turkey distribution. It gets the signals directly from petrol injectors but I can't understand how petrol and lpg fuel trims can differ like this after a while.
To clear the Wideband issue, it's a 5 wire AEM UEGO. We installed the sensor to the empty slot which is there for the bank 2 downstream sensor(which our rigs don't have). So we keep the two upstream narrowband bosch sensors.
BTW the upstream sensors are universal as I mentioned but I can watch the a/f ratios via wideband gauge and there seems to be no problem. They switch nicely though.
We have access to lpg and obd at the lpg installation garage via a generic obd reader and the original lpg interface connection.
Just like today, it always drops similar faults like -too rich, too lean- therefore we can see the problem of lpg and petrol fuel trim difference.
I'll try the cruise test with obd reader and laptop for lpg interface this Friday. I'll also add the info here, hope you can understand the situation more clearly.
 

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Hi, I don't know the Teleflex system (Romano, AutogasItalia, Tartarini and AC Stag, but not Teleflex)

Hope you don't mind, but have a few more questions -

Out of interest have the converters you used done many Bosch engined RRs?
Where did they drill the manifold? Would you have a photo of injectors and manifold?
When you say it goes rich and lean - does one bank go rich and one lean?
I assume the installers have checked out there is no problem with lpg vapour pressure or any faults on injectors?

As to the trims there really should be very little, if any, difference in short term trims between the 2 fuels. If there is either there is a fault, poor calibration, poor installation or the system is not suitable for your car. Although any reasonable full sequential system should work.

ps tried googling Teleflex - a lot of the links didn't work and those that did were all in Turkish. Don't suppose you have a link to website - particularly lpg software as I would be interested in having a look.
Cheers
 

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I would have a guess at you LPG regulator diaphram has become a little relaxed which has leaned off your LPG mixture. The Engine ECU has adapted for this when running on LPG. When you switch over to petrol you are still running the trims for the gas so you end up over fuelling. This is why it runs OK on petrol when you do a reset.
 
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