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[Andy H]

The hunting is different. Ie slight rise and fall in idle speed.

"Grumpiness" is slight missfires causing rough running. In my case its bad enough to bring the eml on, raise 0300 multiple random missfires twice (I'm sure there will be loads of missfire codes not present in there too) and cause 0173/0170 fuel trim malfunction on both banks.

Going by the way the engine behaves, these codes are most likely caused during the cold running on lpg below say 70c on the dash. It really should be able to run at 40c , seeing as behaved fine previously, it was fine at 40c switch over in my other car, and, afaik, all the other kits members have here are all fine switching to gas at 40c at least.

So, what causes multiple missfires on both banks and fuel trim malfunction both banks?
Alli can think of is maf, seeing as I've checked for air leaks.

What causes the same symptoms on lpg prior to a warm engine? No idea. Hoping maf, but we'll see.

Iirc, Kev said the maf also reports intake temp as well as volume on the Dbw engines. Maybe the maf temp sensor is fubar...?

Can't see the MAF working fine on petrol but not on LPG

I still think you need to be looking at the vapouriser (or something associated with it) maybe restricted coolant flow or crud in the coolant passages preventing heat transfer.

Can you borrow a known good vapouriser to see if it makes a difference?

[TheBoy]

Actually, lamdas will be working by then

Yes it's weird. Seems to go well enough when warm on gas. Fine on petrol at all times, its just getting it warm enough to run on gas. 

You have facility to monitor lamdas during this period

[Kevin Wood]

Something's not right. Mine has had a bust vap. temperature sensor for months, so it switches over as soon as I exceed 2,000 RPM, so about 100 yds up the road. Doesn't miss a beat. 

[TheBoy]

Something's not right. Mine has had a bust vap. temperature sensor for months, so it switches over as soon as I exceed 2,000 RPM, so about 100 yds up the road. Doesn't miss a beat. 

The KME vap/AC injector do seem to be more sensitive to setup. My old MV6 never skips a beat (high rpm changes lag aside) - Valtek injectors, can't remember which vap

[feeutfo]

Something's not right. Mine has had a bust vap. temperature sensor for months, so it switches over as soon as I exceed 2,000 RPM, so about 100 yds up the road. Doesn't miss a beat. 

Car is exactly the same as last we played with it. Sometimes its ok, usually on warmer days. Sometimes its missing up to 80c on the dash. But always fine once warm at 85 plus

Problem is it needs to be cold to catch it paying up, if I drive it over to yours, it will be too warm and behave normally. As it did last time.

[feeutfo]

The hunting is different. Ie slight rise and fall in idle speed.

"Grumpiness" is slight missfires causing rough running. In my case its bad enough to bring the eml on, raise 0300 multiple random missfires twice (I'm sure there will be loads of missfire codes not present in there too) and cause 0173/0170 fuel trim malfunction on both banks.

Going by the way the engine behaves, these codes are most likely caused during the cold running on lpg below say 70c on the dash. It really should be able to run at 40c , seeing as behaved fine previously, it was fine at 40c switch over in my other car, and, afaik, all the other kits members have here are all fine switching to gas at 40c at least.

So, what causes multiple missfires on both banks and fuel trim malfunction both banks?
Alli can think of is maf, seeing as I've checked for air leaks.

What causes the same symptoms on lpg prior to a warm engine? No idea. Hoping maf, but we'll see.

Iirc, Kev said the maf also reports intake temp as well as volume on the Dbw engines. Maybe the maf temp sensor is fubar...?

Can't see the MAF working fine on petrol but not on LPG

I still think you need to be looking at the vapouriser (or something associated with it) maybe restricted coolant flow or crud in the coolant passages preventing heat transfer.

Can you borrow a known good vapouriser to see if it makes a difference?

Well. Lpg is harder to ignite, so if something's not quite right, it will misfire before petrol does.

But other than that....

[Kevin Wood]

Could do with something that can record live data from a cold start for the warmup period, really.

Tech 2 probably can't record enough duration. Might be able to find some software for my ELM cable that would, I suppose?

[Kevin Wood]

Actually, what size are your injector nozzles?

I'm thinking LPG is more dense when cold, we know those injectors are marginal on flowing little enough gas for a stable idle at the best of times. I wonder if under some conditions, when the vapouriser hasn't got properly hot, it's overfuelling. This will cause it to stall and mess about in a big way, because as the ECU tries to trim the fuel back, the LPG injectors go below their open/close time and simply stop opening, main ECU sees a misfire and starts to cut cylinders and it grinds to a halt.

I'm guessing it's fine for the first few minutes, then the lambda sensors wake up and it all goes pete tong?

I'm also still mindful of the weird effects we saw with respect to the vapouriser temperature wandering around when we last had a look at it.

If I'm right, turning the vapour pressure down a fair bit (might have to accept that it'll run lean at the top end and avoid this part of the map) might prove if that's the issue.

Oh, hang on.. Chrisgixer avoiding top end. Can't see that working.

Failing that, you come over some time and we gorge ourselves on home brew and curry, stay the night and we have a look in the morning.

[TheBoy]

we gorge ourselves on home brew and curry, stay the night and we have a look in the morning.

All of a sudden, my LPG is broken


Joking aside, TBE has a habit of stalling after about a mile from cold, though its usually hunting bad. In my case, I think its the nozzles are too large, and can't deal with idle. It idles when hot, but is really bad when cold.

[doz]

Today as it was slightly warmer my car didn't go into "rev pogo" mode. Just settled down to a nice idle as soon as the gas cut in. So I'm going to do the technical/mechanical thing and ignore it 

[feeutfo]

My nozzles are 2.2. Same as the other kits, excepts TB's at 2.5mm. (Lazy Bloody admin )

I expect the hunting issue as they all seem to do it with this kit. It's no biggy.

But the miss firing is something that developed on the particular car. It never used to do it. Iirc it was fine last winter.

Problems started on the way back from the lakes. Lag, less eager acceleration ...re mapped re calibrated etc seemed ok, but the grumpiness remained.

IMO it's not a set up issue as such. Something has gone out of tolerance. Something specific to this car. Not the kit.     ...afaict anyway.

What affects cold starts, on both banks, just prior to proper operating temp?

Seemed ok this morning on cold start, very minor grump at junction just after switch over. But no extra codes, no light on, drove off fine.

Car seems more lively, but that could be placebo.

I have the LPG software and still have Kevs cable, so could record, if only I knew how, and had another set of hands.


Wonder if it needs re calibration to this maf.

Oh, and vap is set at 1.2 bar currently, I noticed.

[doz]

I know it may seem daft but when did it last have a set of plugs? We know the LPG does punish the ignition side of things. Just a thought I'll go stand in the corner again now. 

[Entwood]

Have you tried an exact replica drive but on petrol only ?? Just to see if there is any recurrence ??

Mine (BRC) is set to change on pressure not temp/time/rpm and has never had any problem ... so I'm sort of wondering if it is a "gas only" problem if it is low pressure at low temps .. in which case changing the switch over slightly so the evap is warmer might help ??

[feeutfo]

I know it may seem daft but when did it last have a set of plugs? We know the LPG does punish the ignition side of things. Just a thought I'll go stand in the corner again now. 

yeah changed the plugs October time iirc, (just checked, it was actually may ) so they won't have done more than 10k.

[feeutfo]

Gave it the full beans onto the 329 this morning where it normally plays up on my commute. Didn't miss a beat.

Two Luke warm starts yesterday, where the temp gauge was still sat at the bottom, but it had some heat in it as it started on gas immediately, so guessing about 50c. No problem. All fine, minimal hunting too.

Test will be the journey home though, especially as it gets colder at the weekend. Historically it really hates crawling along in traffic in the cold. (From switchover to 80c+)