LPG - I've got problems.

[JamesV6CDX]

Actually, just thought. Can you get the screen up on the LPG software where there's an "oscilloscope" display of all the parameters, wait for it to falter and then capture the screen then post it?

Kevin

I'll do it asap

[JamesV6CDX]

I have the screen dump, will post up in a mo

This problem is DEFINATELY related to the outside temperature... today it was about 6 degrees warmer, and once the engine was up to temp, it hasn't faltered once all day on gas.... whereas before it was hunting after a 50 mile run!

Is there too much cold air getting in then? Would it be too much of a bodge to "restrict" the intake a bit for the winter (or even as a test?)

**looks at the gaffa tape....**

[Kevin Wood]

I have the screen dump, will post up in a mo

This problem is DEFINATELY related to the outside temperature... today it was about 6 degrees warmer, and once the engine was up to temp, it hasn't faltered once all day on gas.... whereas before it was hunting after a 50 mile run!

Is there too much cold air getting in then? Would it be too much of a bodge to "restrict" the intake a bit for the winter (or even as a test?)

**looks at the gaffa tape....**

Yes. MAF is measuring the volume and temperature of air entering the engine and providing the appropriate amount of fuel. The inlet is already pretty well restricted at idle - by the throttle.

Have any of the parameters on the LPG ecu changed dramatically since it was cold?

Kevin

[JamesV6CDX]

None whatsoever Kevin, on the software, it's all as normal as it's ever been....

Last night I factory reset the ECU, and set it up again, inc calibration and fuelling.

It goes like something off a shovel on LPG now..

I did consider a pottential dodgey MAF (I have a MAF code 73 stored)... but I was getting this code before, and have since replaced the MAF with a known good...

[Kevin Wood]

So... Air temperature seems to be an issue. In theory the inlet air temperature sensor should be compensating for this and, in addition, it should be closed loop so the lambda sensors are also correcting the mixture - assuming the sensor voltages were cycling. Vapour temperature could be another variable but I guess it doesn't lose that much heat between vapouriser and engine and, again, any discrepencies should be taken out of the equation in closed loop running.  :-/

Makes me wonder if there's some grease in the injectors that's getting a bit thick in the cold and causing them to stick - but surely a good run would free them off?

I believe Jay W said he had to strip and clean one of his injectors to clear his misfire. May be worth a shot. Seems odd that a Polish LPG system has problems in the cold.

Kevin

[cem_devecioglu]

Maf can be (worth trying half blocking the air inlet) or

I think LPG stochiometric map cant balance very cold temperature (if its trying)

[Kevin Wood]

Just wondering, to confirm it's air temperature related, can you remove the intake ducting from the bottom of the airbox and bodge something to draw warm air from behind the rad?

Kevin

[JamesV6CDX]

Just wondering, to confirm it's air temperature related, can you remove the intake ducting from the bottom of the airbox and bodge something to draw warm air from behind the rad?

Kevin

Not a bad idea at all.. and one I have considered.... I think it's worth a go...

[JamesV6CDX]

I went out from cold tonight, and it was absolutely fine, no falter whatsoever, and loads of power on gas. MID read 1.5 deg C...

As silly as this sounds, I have been using one particular gas station. I might try filling up somewhere else, just to eliminate another variable (albeit an ulikely one)

I saw a post on another forum earlier about suspect LPG from some garages.

For example, I think if Taxi Driver fills up at BP (Where I have been) His Emissions light comes on...

[JamesV6CDX]

Screen shot of graph, just after the blip:

[bconnelly]

It doesn't cure your problem but mine has been a wee bit rough idling since the temp dropped <-3. Lets see if it improves with the weather!!

[Martin_1962]

COuld be butane mixed in?

[Kevin Wood]

Hmm. Damn jpeg has fubar'ed the colours

I think the RPM line is wandering between about 1000 and 400 RPM. Uncommanded, I take it?

LPG pressure looks stable throughout so the evaporator seems in the clear. LPG injector duration seems to follow petrol injector duration which isn't exactly stable - cause or effect? :-/

Lambda sensors are cycling, a little unstable but, again, difficult to tell if that's because the ECU is trying to adjust idle or because the fuel is all over the place.

It's really difficult to see how a few degrees of air temperature could make a difference. Correction required due to air density would easily be taken out by the Lambda correction even if the IAT wasn't doing its' job.

I'd go with the dodgy fuel theory I think.

I'd say see how it goes for a while....

Kevin

[JamesV6CDX]

That graph was after about 15 mins of running on a cold day, with no input from me. It was just left to it's own "idle" devices...

Funny enough, last night I put half a tank of LPG from another garage in, I wonder if this is why it feels better today...

On this basis - I guess I'm going to have to drain the tank - Go fill up at Shell, and see what happens from there!

I do still intend to monitor the fault codes on the engine ECU, and see if anything persistent comes back that could be causing the issues...

Martin, re. your butane comments - I have read that some garages put 30% butane in the mix - and this makes it more economical?

I do intend to get to the bottom of this - other than the intermittent idle on gas, this car is close to perfect..

[JamesV6CDX]

I think the RPM line is wandering between about 1000 and 400 RPM. Uncommanded, I take it?

Totally - this is the hunting...