LPG High Idle and Petrol 'Hunting' Idle on 1.3 EFI 16v HiJet

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Re: LPG High Idle and Petrol 'Hunting' Idle on 1.3 EFI 16v HiJet

Post by El_Ventu on Sun May 26, 2013 11:55 am

Have you checked for breakage of one of the vacuum pipes connected to the manifold?

I had a similar problem with mine, I think there is a good possibility to find the problem between the various pipes.
Engine behavior is the same.

Sucking not carburized air (I know that there's no carburettor, but the meaning is the same, ECU can't sense that air, and at idle the engine runs in open loop) on petrol causes the idle to increase, it increases to the point when ECU enters in cut-off zone, then cutting the fuel allows the engine speed to fall under the cut-off regime, and so on.

On LPG you have a mixer, than the cut off, if present, is not so precise.
The behavior is the same (for ECU) than in petrol, but the idle remains about stable, but high, because of the hysteresis of the LPG cutoff and the low gas flow.

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Re: LPG High Idle and Petrol 'Hunting' Idle on 1.3 EFI 16v HiJet

Post by HiJetSi on Sun May 26, 2013 2:09 pm

I have now checked and...I think I may have found my problem... Very Happy

This is pictured under the drivers seat...off to the scrapyard I go!!





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Re: LPG High Idle and Petrol 'Hunting' Idle on 1.3 EFI 16v HiJet

Post by HighlyJetted on Sun May 26, 2013 2:19 pm

That won't cause it to hunt.

Telling you, if you don't get water through the idle control valve it will always hunt.

Hunting is the ECU trying to hold the target idle.

While the idle control valve is cold or has no water, it stays open to increase the idle speed. E.g. more intake air

Once the engine is warm the idle should drop because the idle control valve closes from the water temperature flowing through it.

Once the ECU see's the water temp is above a certain point, it then controls the idle by altering fuelling amount.

Because the idle is way to high, it cuts the injectors pretty much 100% for a moment, which causes the revs to drop down, and then to stop it from stalling it turns them back on.

At which point it thinks the idle is too high, so it cuts the injectors..... etc etc! The hunting loop.
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Re: LPG High Idle and Petrol 'Hunting' Idle on 1.3 EFI 16v HiJet

Post by HiJetSi on Fri May 31, 2013 2:29 pm

UPDATE:

- Blew compressed air through return pipe connected to idle control valve.
- Radiator cap was open to let air escape.
- Immediately Stopped blowing air when heard water escape from Radiator cap.
- Put radiator cap back on.
- Turned engine on (with hexagon branch pipe blocked)
- Let it get warm and waited for water to come out of return pipe...no water out of return pipe, but I did get bubbles in the coolant reserve tank and a very slight amount of water out of return pipe...

Now perhaps I went wrong at this stage by not letting it run till water came out...BUT i reconnected the pipes as they should be when cool again and once the bubbles stopped in reserve tank.

-Ran the engine as normal
- Then the idling problem was much more intermittent than before rather than constant idle hunting.

Now when its up to temperature it idles relatively smoothly, just a little higher than it should do, only sometimes hunting.

SO I am now thinking that I should:

- Block up branch pipe again.
- Blow some more compressed air through idle to be sure there are no more blockages.
- Run system until water comes out of return pipe and air is out of system.
- Seal return pipe.
- Reconnect all when cool?!

What do you guys think?!

Cheers!

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Re: LPG High Idle and Petrol 'Hunting' Idle on 1.3 EFI 16v HiJet

Post by HighlyJetted on Fri May 31, 2013 9:29 pm

I'll tell you what I do, right or wrong.....


I use a header tank, well a watering can actually.

I fill it with coolant, with a length of hosepipe attached to the spout.

I have some rubber hose that fits inside the radiator filler point, and the hosepipe fits in that.

I tip the watering can spout down, then I rest it on top of the open sliding door.


Now this gives me a "head" or pressure filling setup.

So I undo various hoses and caps etc to bleed the system.

So I can part the hose for the idle control valve, put my finger over the hose or the pipe fitting so I can get the water through everywhere.

I ensure the watering can never runs out of coolant, as this means I get air in the system - defeating the point.

It takes me about 12 litres of premixed 40/60 coolant to fully fill and bleed the system.

Ya digg?
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Re: LPG High Idle and Petrol 'Hunting' Idle on 1.3 EFI 16v HiJet

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