Random Misfire Cyl4

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Brian_H
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Re: Random Misfire Cyl4

#21 Post by Brian_H » Fri Nov 29, 2019 9:12 pm

To me that sounds like quite a lot, though a lot of short journeys or a high switchover temp might cause it, or having to run on petrol having run out of LPG of course.

There isn't much in the thread so far, but it may be worth you trying to rule out the lpg injector by swapping it around if your able to do so (difficult to tell without knowing the injectors, but if you can swap both the lpg hose coming out of the injector and the electrical connector with one close to it - making sure you keep the same hose going to the same injector as the plug and know where to put them back afterwards!)

If you did want someone to look at it, Simon (LPGC who has replied to the thread earlier) is in Yorkshire, so may be an option for you and could certainly give you an idea of what needs doing to fix it/be able to fix it for you.

dazza007
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Re: Random Misfire Cyl4

#22 Post by dazza007 » Sat Dec 07, 2019 8:47 pm

Thanks Brian.
That sounds like a good suggestion something to look at. The injector are omvl cleaned a couple of months back.
I have been running torque pulling data, difficult to get a full picture as Suzuki use a specific Scanner. Changed my MAF sensor idles a little better no registered misfires now just pending. It is a bit confusing how the lpg ecu interacts with the system sensors such as the MAF/O2 sensors? I am sure that the oxygen sensors will be replaced soon as they are not tracking eachother.
I ordered some petrol injectors for the car. Unfortunately the lpg injectors need to be moved to fit the petrol injectors. Having a little difficulty finding how to remove the lpg rail, the omvl rail is bolted to the engine. If I can get the lpg rail out of the way to remove the injector rail would this work?
Fortunately replacing petrol injectors is relatively straight forward although costly :)

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Re: Random Misfire Cyl4

#23 Post by Brian_H » Sat Dec 07, 2019 9:46 pm

If its the OVML SL injectors (rail of 4 in a row with blue coils) its as simple as removing the hoses from the injectors, unplugging them and removing the two nuts securing them to the engine. Depending on the clips used to secure the outlet hoses, this may be very simple or may involve replacing the clips. Though if you can't easily remove them you may be able to disconnect the rest of it and move them out of the way. (there are some exceptions to this on older systems, where there is a connection to the lambda sensor, but most newer systems don't use this as its more effective to look at the trims being applied via obd than to try adjusting by lambda reading).

LPG system doesn't directly interface with either the MAF or O2 sensors. What its doing its intercepting the petrol injection signals, applying them to its own map to control the lpg injectors and isolating the petrol injectors (unless its adding some additional petrol, which some setups do to prevent VSR, but if its doing so thats under control of the lpg ecu at that point). You can find some systems will connect to OBD to try to adjust trims, but this isn't usually recommended as it rarely works too well.

Provided the petrol system is working as it should, and the lpg is calibrated correctly, then this shouldn't make any difference on either fuel. If you have a lambda sensor not reading correctly (I don't think its as simple as comparing the sensors, the second one in the system is only there to see if the cat is effective as with a working cat it should see less oxygen in the exhaust after going through the cat than before, so the two readings shouldn't be identical anyway) then you may be better to start there. If your using torque it should be possible to do some logging with it, if you can set that and post what its doing here, then someone might have some better observations than me on it.

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Re: Random Misfire Cyl4

#24 Post by LPGC » Sat Dec 07, 2019 10:25 pm

It is possible and likely that 'routing' is incorrect - Only fitted 4 years ago your ECU will be the latest generation OMVL which means that it at least follows petrol fuelling strategy for the most part (follows petrol injector 'firing' operation order and adjusts pulse length for individual injectors - Much earlier OMVL ECUs don't follow petrol firing order etc) but it can only do this properly if it is wired properly... In this respect being wired properly means 'routing' is correct, by routing we mean that each LPG ECU output channel (gas injector electronic output) matches up to the same cylinder/channel for petrol injector input. If routing is incorrect then during changeover for brief moments when petrol injectors are being turned off (each in turn) while LPG injectors are being turned on (each in relative turn) then some cylinders will receive no fuel (misfire) while another cylinder receives both petrol and LPG (misfire due to double the amount of fuel). On a 4 cylinder engine if routing is wrong for one cylinder it must also be at least wrong on another cylinder (so if wrong at all must at least be wrong on 2 cylinders) and due to this at least 2 misfires would occur during changeover.

Other possibles include pressure rising too high when there is no 'bleed'' (gas take-off from the reducer) at the point (time) of changeover / injector to manifold pipe lengths too long / manifold nozzles too far from inlet valves / incorrect calibration / broken vapour temp sensor / all the other possibles mention by others in above posts.
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dazza007
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Re: Random Misfire Cyl4

#25 Post by dazza007 » Sun Dec 08, 2019 10:41 am

Thank you so much. There is a lot to think about there.
Here is the torque data https://1drv.ms/u/s!Av9BZXz47n0Dri3Y2_t ... p?e=ZTLmrW

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Re: Random Misfire Cyl4

#26 Post by dazza007 » Sun Dec 08, 2019 6:19 pm

So I have a registered misfire, Freeze Frame data
Freeze frame report generated by Torque for Android
=========================================================

Vehicle VIN: Not present
Vehicle Manufacturer: Unknown
Vehicle Calibration ID: 33980-78K2*00000

Freeze frame information:
------------------
Engine Load = 33.333 %
Engine Coolant Temperature = 20 °C
Fuel Trim Bank 1 Short Term = 9.375 %
Fuel Trim Bank 1 Long Term = 2.344 %
Engine RPM = 1,349.75 rpm
Speed (OBD) = 0 mph
Timing Advance = 8 °
Intake Air Temperature = 7 °C
Mass Air Flow Rate = 8.63 g/s
Throttle Position(Manifold) = 19.216 %
Run time since engine start = 48 s
Barometric pressure (from vehicle) = 13.924 psi
Voltage (Control Module) = 14.434 V
Engine Load(Absolute) = 25.882 %
Relative Throttle Position = 7.059 %
Absolute Throttle Position B = 35.294 %
Accelerator PedalPosition D = 14.902 %
Accelerator PedalPosition E = 7.451 %


End of report.

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Re: Random Misfire Cyl4

#27 Post by Gilbertd » Sun Dec 08, 2019 6:24 pm

Running on LPG with a coolant temperature of 20 degrees C? Not surprised it is misfiring.
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dazza007
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Re: Random Misfire Cyl4

#28 Post by dazza007 » Sun Dec 08, 2019 9:51 pm

Thank you
It is still on petrol "Run time since engine start = 48 s"

Brian_H
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Re: Random Misfire Cyl4

#29 Post by Brian_H » Sun Dec 08, 2019 10:31 pm

What switchover temp is set in the LPG software? 20 degrees is possible to set on some ecus, but not recommended.

If its left after running, does the pressure in the lpg system hold, or does it drop? You can monitor this with the engine running whilst on lpg by switching back to petrol, though suspect you may only see it when its started from cold (I'm thinking you might find the reducer has failed and is leaking gas via the vacuum connection or an gas injector, causing one cylinder to misfire. Do you know/can you see where the vacuum feed for the lpg system is taken from (might be a dedicated point, or may be taken from an existing vacuum line? Is it close to cyl 4 specifically?

Equally the tests listed by Simon may identify that if it is the problem, if your going to replace petrol injectors, then check the wiring against the wiring diagram for the lpg system, you should see channel 1/a matching the same cylinder as the pipe from injector 1/a on the loom - if nothing else, make a note of the colours there and post what you've found here).

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Re: Random Misfire Cyl4

#30 Post by dazza007 » Mon Dec 09, 2019 8:24 pm

I haven't managed to look at the ecu for the lpg and need to.
A few questions - I noticed that when trying to moving the injector some gas came out feeding c4. I am pretty sure that the misfiring is occurring on petrol. If this injector line is not 100% sealed could this cause a misfire prior to the switchover to lpg? Can't smell gas when the engine is running. The lpg injector end at c4 is moving slightly with the engine (opposed to c1 which is fixed) I guess this action would of loosened the injector tube.
I am pretty sure that the petrol injector at c4 needs replacing, it would have been easy but the lpg system is a web.
Am i barking up the wrong tree thinking this is the petrol injector as the misfire is occuring prior to the switchover?
I need to fully remove the lpg injector system to get to the petrol injectors, if i remember correctly I just release the pressure and the tank closes the valve?
If both injectors come out and go back in at least I can tick this off !

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Re: Random Misfire Cyl4

#31 Post by Brian_H » Mon Dec 09, 2019 8:40 pm

The tank will be closed as long as the valve hasn't been played with, if you want to play it safe, the easiest way to remove the gas from the system after the tank is to either close the valve on the tank, or disconnect the rear solenoid and let the engine run till it cuts back to gas (might take a few moments to do that). Otherwise loosen the hose that feeds the injectors carefully and somewhere with decent ventilation.

But if your saying its loose, I'd suspect you might have a vacuum leak there - and that might actually be the source of your misfire anyway. Do you mean the spud (the bit screwed into the manifold with the hose on it) is loose? Or some other part?

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Re: Random Misfire Cyl4

#32 Post by dazza007 » Mon Dec 09, 2019 10:10 pm

Thanks Brian,
The hose was loose at the injector

Brian_H
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Re: Random Misfire Cyl4

#33 Post by Brian_H » Mon Dec 09, 2019 10:23 pm

That should be easier to fix - is that just a loose clip, or damage to the injector? If its the spring type clip maybe it isn't positioned properly, but I'd suspect its a compression type clip, so you might need to replace it if you can't do anything else with it. At a push a petrol hose clip of a suitable size could be used to sort it out. May be a case of replacing that section of hose if the hose has gone hard and won't seal because of that.

But none of that should be a major job provided you can get to the bits in question.

dazza007
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Re: Random Misfire Cyl4

#34 Post by dazza007 » Tue Dec 17, 2019 9:37 pm

So went to lpg garage near Kirkby Longsdale
Smoke test little leaks found
C4 leakdown test is fine less than 5% c3 and c1 on 9%
Disconnected Lpg wires piggy backing on injector 4. Car felt different, before if you put the foot on the gas it felt like it had a turbo, now there is no lag. Got to see if it misfires on petrol now if so wire in lpg injector and disconnect inject to a non connected injector (petrol 4>3 cylinders) to check gas.
Fingers crossed

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