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[wingman]

Since having my Elite converted to LPG (Zavoli System) I have a couple of probs that I hope you meega experts might be able to help with.
The first is an EML generated by Fuel Trim Malfunction codes (0170 and 0173). There was originally an air leak on the plenum breather bridge O ring that's been fixed, codes cleared (inc 0170 & 0173) but some 150 miles later the EML light is back. What is a "Fuel Trim Malfunction" and what could cause it.
The second prob which may be related is the idling speed which intermittently seems to hunt when in neutral between 750 -1500 when the engine is hot. I don't think I have any more air leaks but is it possible that could be the cause? (O ring seal on plenum?)
I would like to check and clean the ICV if my 3.2 has one but don't know where it is on this engine or what to clean it with.
Any help greatly appreciated

[Marks DTM Calib]

Question has to be, does it run ok on petrol?

[Kevin Wood]

Fuel trim means the ECU has had to correct the amount of fuel injected to a greater extent than is allowed. As Mark says, does it do it on petrol?

If not, I'd suspect the tuning of the LPG system is not as good as it should be, or it's not delivering the volume of gas it should be for some reason (clogged filter, incorrect vapour pressure, heavy ends in the vapouriser...).

There is no idle valve on the 3.2 but it may be worthwhile to clean the throttles in case these are dirty keeping an eye out for possible air leaks however the hunting could also be a symptom of the mixture being wrong. Does it hunt on petrol in addition to LPG?

Kevin

[wingman]

Thanks for info on this and prompt replies!
The idling seems OK on petrol. Don't know whether the EML will be generated on petrol as I don't know how to clear the codes and then run on petrol to check. Can this be done without a Tech 2 session?

[Kevin Wood]

A cheapo Tech 2 or an ELM based code reader would do the job. Or, the EML would probably extinguish after driving on petrol for a while. Not sure how long "a while" would be in this case though.  :-/

I'd be happy to have a look for you but it's a bit of a trek between us.

With a decent code reader or Tech 2 you could watch the fuel trims in real time as you switch between fuels and that would tell us a bit more about what's going on.

Kevin

[wingman]

Thanks for that and the offer Kevin.
The guy who installed it is quite willing to have it back and look at it and has been very helpful but he is away until beginning of October and I was trying to see if I could get to the bottom of this before then.
I will do as you say and run on petrol for a "while" and see what happens to the EML. Am I right in saying that I thought you may be able to clear codes by leaving battery disconnected for 24hrs or so? Installer does have a code reader but did have trouble clearing these codes before.
I may like to take you up on your offer to take a look at this if the installer cannot come up with an answer!!

[Kevin Wood]

OK. No problem. Disconnecting the battery will not clear the codes, unfortunately.

If you need a hand that's no problem at all. It would be good to have the software to access the LPG ECU if you have it, but without, we can at least see what's happening even if we can't fix it.

Kevin

[wingman]

Kev/Mark - as suggested have driven exclusively on petrol since last post and EML has gone but fault codes still there (0170,0173,0443). The idling problem was still there on petrol though, not as I said before only on LPG. Today the LPG installer and I have replaced plenum O rings just in case these were leaking (original 0443 was caused by top hat O ring on breather box which was changed about 3 weeks ago), cleared codes and recalibrated for the LPG setup all OK. However idling prob in neutral still remains both on petrol and LPG. The best way I can describe it is like an internmittent sticking mechanical throttle but with the additional "benefit" of hunting between about 1000 - 2000 rpm when it happens. Seems to be slightly worse on LPG than petrol and only happens when engine is hot. When fans cut in idling sometimes seems to return to normal 750?
As I know nothing about these drive by wire throttles is there anything obvious that I can check. I have already looked at the plugs and vacuum connexions around the throttle body and assume that the control is the unit on the drivers side of the throttle body at the front of the plenum.
Any advice would be most welcome before a trip to Hants is deemed necessary Kev.

[Kevin Wood]

The codes will probably remain until cleared but the EML off means the fault has not occurred recently. Does it come back on when you run it on LPG now?

Idling problem is a bit of a mystery. The throttle body can be cleaned out with some carb cleaner and a rag and you can check that the throttle moves smoothly by carefully turning the shaft by pressing on the throttle plates. It should rotate closed again against a spring.

Other things to check are that the injectors are wired correctly. It could be that a couple of them were swapped over when the wiring was modified during the LPG conversion.  Still could well be an air leak somewhere though.

Kevin

[wingman]

All codes have been cleared and will now see if they come back whilst running on LPG.
Petrol Injector wiring was not touched AFAIK. Installer mounted LPG injectors ontop of plenum and drilled and tapped the plenum with the LPG feeds which then have straws which feed down to ontop of the valves. AFAIK the only wiring altered was to intercept the feed to the petrol injectors so that it goes via the LPG ECU. The engine ECU then feeds its signals via the LPG ECU which when running on petrol just passes the injector signals through itself, and when running on LPG diverts the engine ECU signals to the LPG injectors. Does this sound right?
Will take a look at cleaning the throttle body tomorrow and will check for free movement.

[Kevin Wood]

AFAIK the only wiring altered was to intercept the feed to the petrol injectors so that it goes via the LPG ECU

Yep, this is what I was thinking. I was just wondering if 2 of the injector signals got swapped over during the process of diverting this wiring. A long shot. I managed to do this during my conversion  . It actually ran OK on petrol but struggled to idle on gas.

Kevin

[Lazydocker]

Easy mistake to make! I'd hope he had to unplug all of them to remove the manifold when he drilled it! :-? :-?

[The Cambelt Kid]

I had EML with fuel trim on both banks which turned out to be the injector nozzles being too narrow.  Since drilling them out from 2.1mm to 2.35mm and a re-calibration on LPG it ran very sweet.

[wingman]

Manifold was not drilled so injector wiring was not disturbed!
Plenum was removed and drilled and straws attached which reach down onto top of valves. Injector blocks were mounted ontop of plenum thus enabling plugs to be changed without moving all of the LPG stuff out of the way.

AFAIK the only wiring change was to intercept the 12V feed to the injector rails and run it via the LPG ECU so that when running on petrol the 12V feed goes straight through and the petrol injectors are controlled as normal by the main ECU. When running on LPG the power to the petrol injectors is cut off and diverted to the LPG injectors via the LPG ECU, the timing of these being controlled (I think!!) still by the main ECU with the LPG ECU being able to modify as required these timings. At least I think thats the way this Zavoli setup works but stand to be corrected by Kevin or another of the LPG experts on the forum. AEB software is used to calibrate the LPG ECU.

Can't look at throttle body for idling prob today as SWMBO has other ideas in how I should spend my time this weekend!! Will look at next week.