High Idle - sometimes

[jughead1]

I recently had my VX Series II (V6) converted to LPG dual fuel, using a second hand Impco system.
Since installation the car idles at various rpm, sometimes 750 RPM, sometimes 1100 RPM, and most commonly, 1250 RPM.

He mechanic said the car has a “sticky throttle”, but couldn’t figure out why. He suggested changing the Oxygen Sensors, which I did, as well as the spark plugs and leads.
But the car is still doing this.

It only does it when running on gas.
Sometimes when I rev it tio around 3000 RPM (on gas) it then settles down to 750 RPM.
Other times I have to switch it to petrol then rev it then switch back to LPG to get it to settle.
But sometimes nothing works.

Anyone have any idea what else I should check for/change?

Cheers,

JG

[accentstencil]

A sticky throttle could be due to a build up of crud in the throttle body where the butterfly opens, that would cause high idle. I would be checking the IAC (Idle Air Control Valve) and giving that a good clean.
I'm assuming that the 70RPM is a typo because it would stall at that.

[jughead1]

Thanks for the quick reply.

I'm assuming that the 70RPM is a typo because it would stall at that.

Yes, that was a typo. I have edited the post to say 750 RPM.

Also added that it only does this on LPG.

Where would I find the butterfly?

Cheers,

JG

[m1lky]

Butterfly is on the engine when the intake pipe meets it

[accentstencil]

Thanks for the quick reply.



Yes, that was a typo. I have edited the post to say 750 RPM.

Also added that it only does this on LPG.

Where would I find the butterfly?

Cheers,

JG

If you take of the big pipe that goes from the throttle body to the air box you will see the part that opens and closes when you accelerate, that is what I mean by butterfly, it may not be called that but in a carby it is.

[jughead1]

That is what I thought you meant. But if that was the problem, I would have expected the car to behave the same way when running either LPG or petrol.

It does not do that when running on petrol, and only started after the LPG was installed, so I suspect it is something to do with the LPG system, but buggered if I know what!!

JG

[VT_SS]

Who did the install ?

[jughead1]

Lake Edge motors at Tumbi Umbi (on the Central Coast of NSW).

[accentstencil]

I was referring to the butterfly for the sticky throttle which your mechanic mentioned.
For the erratic idle I would still check and clean the IAC valve. Although I don't know anything at all about LPG and if the IAC is used when switched to LPG

[VT_SS]

Lake Edge motors at Tumbi Umbi (on the Central Coast of NSW).

The reason i ask is what were the conditions on installing the secound hand LPG ? was the car running fine when you handed the keys to the mechanic ?

[jughead1]

The reason i ask is what were the conditions on installing the secound hand LPG ? was the car running fine when you handed the keys to the mechanic ?

The car was running fine, but the mech did say there is no warranty on the equipment itself - just on the install.

He spent an extra day trying to get the system to work correctly, and was very pissed off that it was nopt working as it should.

He did mention that the system was not up to his standard (I bought it on ebay from a guy in melbourne).

Unfortunately at the time (and still now) I did not have the money to get a new system installed. So this was the best I could do.

JG

[VT_SS]

The car was running fine, but the mech did say there is no warranty on the equipment itself - just on the install.

He spent an extra day trying to get the system to work correctly, and was very pissed off that it was nopt working as it should.

He did mention that the system was not up to his standard (I bought it on ebay from a guy in melbourne).

Unfortunately at the time (and still now) I did not have the money to get a new system installed. So this was the best I could do.

JG

Thats a hard one mate maybe cut your losses and take it off if it isn't easily fixed.

[jughead1]

The car is running fine, even with the un-even idle. It is just running a little less economically than expected. But it is still cheaper than running it on petrol. I drive around 850 KMs a week, so it makes a big difference.

Thanks for all the replies.

Cheers,

JG

[Ghost]

Ask the installer if he changed the memcal because if he didnt then u may need a tune setup for LPG

[VT_SS]

Ask the installer if he changed the memcal because if he didnt then u may need a tune setup for LPG

Xcler8 makes a good point have it checked out.

[jughead1]

What exactly is the MEMCAL?
And where is it located?

Cheers,

JG

[Ghost]

The memcal is inside your ecu the memcal is made up of settings that control the engine and sensors and gearbox as well

[jughead1]

Ah, OK. It is the computer chip?

Would that cause the idle to change from 750 to 1000 to 1250 RPM at various times?

Also, is there a sensor that tells the engine the temp, so it will idle high till the engine is warm, then reduce the idle?
(Although I don't know why the idle would be normal in petrol but not in LPG.)

Cheers,

JG