Engine misfire .
Hi,
Joined your LPG Forum today .
I have a Mercedes E 200 converted to LPG in 2006 ,has STAKO – OMVL.
History of engine misfire ( usually first thing in the morning ) solution stop engine and restart
Spark plugs changed last week ,Mechanic checked Engine management system (petrol) on laptop ,No errors found ,in his opinion could be a valve/solenoid problem on LPG side ,( when I manually switch back to petrol engine misfires) reading some of the post's seem to suggest the LPG system needs to be serviced , should I start saving for this ?
Cheers
Lampsout.
Merc engine misfire.
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Taught2BeCautious
- Member
- Posts: 52
- Joined: Thu Jun 21, 2012 7:15 pm
Re: Merc engine misfire.
There might be a few things you could do yourself quite cheaply - like replacing the vapour-phase filter and cleaning out the liquid-phase filter (if you have one - usually part of the solenoid valve in the engine compartment, close to the vaporiser).
Do you know how the new spark plugs were gapped? You need a slightly smaller gap when running LPG.
What year is the car?
Were there any 'pending' DTC's (Diagnostic Trouble Codes) logged in the ECU - or did the mechanic not check those? Usually a misfire would be flagged as a code like 'P030x' (the 'x' being the cylinder number), so you could tell which cylinder(s) were at fault. An intermittent misfire sometimes doesn't log as a permanent fault code, but should show as 'pending'.
If the misfire is on the same one or two cylinders, it could be a faulty coil-pack. If it is at random across all cylinders, its probably fuel related.
If you can access the LPG system configuration, have a look at the settings to see if they are within the recommended ranges.
Alan.
Do you know how the new spark plugs were gapped? You need a slightly smaller gap when running LPG.
What year is the car?
Were there any 'pending' DTC's (Diagnostic Trouble Codes) logged in the ECU - or did the mechanic not check those? Usually a misfire would be flagged as a code like 'P030x' (the 'x' being the cylinder number), so you could tell which cylinder(s) were at fault. An intermittent misfire sometimes doesn't log as a permanent fault code, but should show as 'pending'.
If the misfire is on the same one or two cylinders, it could be a faulty coil-pack. If it is at random across all cylinders, its probably fuel related.
If you can access the LPG system configuration, have a look at the settings to see if they are within the recommended ranges.
Alan.
Re: Merc engine misfire.
Hi Alan, Thanks for you reply .
Year of car 2001 Merc - Compressor .
Mechanic says there were no pending Diagnostic faults.
I am not up to speed on LPG Mechanics so I would not know where to start or find the LPG parts .
Spark plug ignition packs have been replaced .
Will reduce the setting on spark plugs .
Have found a local LPG installer /Mechanic says it could be anything causing engine misfire but has to get the software before he can run a diagnostic check on LPG system , it will be a couple of weeks before he can look the car .
I think the The LPG system is kicking in too early before the car engine has reach normal operating temperature, I am running on petrol and manually switching on to LPG which seems to work.
Reading members post's my LPG Merc needs a service .
Will let you know how I get on thanks for your help.
Mac .
Year of car 2001 Merc - Compressor .
Mechanic says there were no pending Diagnostic faults.
I am not up to speed on LPG Mechanics so I would not know where to start or find the LPG parts .
Spark plug ignition packs have been replaced .
Will reduce the setting on spark plugs .
Have found a local LPG installer /Mechanic says it could be anything causing engine misfire but has to get the software before he can run a diagnostic check on LPG system , it will be a couple of weeks before he can look the car .
I think the The LPG system is kicking in too early before the car engine has reach normal operating temperature, I am running on petrol and manually switching on to LPG which seems to work.
Reading members post's my LPG Merc needs a service .
Will let you know how I get on thanks for your help.
Mac .
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Taught2BeCautious
- Member
- Posts: 52
- Joined: Thu Jun 21, 2012 7:15 pm
Re: Merc engine misfire.
2001 models should have the 16 pin OBD2 diagnostic connector, so a standard fault-code reader should help. I have one permanently connected to my 2002 Vaneo, which doubles as a trip computer.
I regularly get fault codes indicating lean-running and misfires on various cylinders, but this is only noticeable when the car occasionally misses a beat when it switches from petrol to lpg when the engine is idling. If it switches whilst being driven, you don't notice anything, but it still throws up a code or two.
It is important to make sure that the car is running 100% on petrol before trying to diagnose faults in the lpg system, but if it is switching to lpg too early after a cold start, you will need to get the lpg ECU hooked up to a Laptop running the correct software to make adjustments.
It's good if you can do these adjustments yourself as they can be quite time-consuming - not just to save money at the garage, but so that you can make adjustments for summer / winter running.
If your local man manages to fix it at a reasonable cost, give him a mention!
I regularly get fault codes indicating lean-running and misfires on various cylinders, but this is only noticeable when the car occasionally misses a beat when it switches from petrol to lpg when the engine is idling. If it switches whilst being driven, you don't notice anything, but it still throws up a code or two.
It is important to make sure that the car is running 100% on petrol before trying to diagnose faults in the lpg system, but if it is switching to lpg too early after a cold start, you will need to get the lpg ECU hooked up to a Laptop running the correct software to make adjustments.
It's good if you can do these adjustments yourself as they can be quite time-consuming - not just to save money at the garage, but so that you can make adjustments for summer / winter running.
If your local man manages to fix it at a reasonable cost, give him a mention!
Re: Merc engine misfire.
Hi Alan ,
Thanks for the info.
Mechanic (petrol) Offered to service the car ,but will not touch the LPG.
Need to find someone in KY 2 area who would guide me around the LPG system , have a bit of reading to do .
Cheers
Mac .
Thanks for the info.
Mechanic (petrol) Offered to service the car ,but will not touch the LPG.
Need to find someone in KY 2 area who would guide me around the LPG system , have a bit of reading to do .
Cheers
Mac .
Re: Merc engine misfire.
Ky2 ? Wheres that ?
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mat_fenwick
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tommo2009
- Intermediate Member
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- Location: South Wales
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Re: Merc engine misfire.
Mercs are a bit of a pain when it comes to missfires. You have already pretty much diagnosed your problem as changing over too early. Could be just a setting in the software that needs changing could be a Vapouriser that is getting past its sell by date.
Could be a coolant flow issue.
Whichever it is you will need someone who can look at the software and see what is happening on changover.
As for the missfire, mercs will shut down the cyinder that is missfiring and it will not reset until the ignition has been recycled, which is why it doesn't disappear when you put it back to petrol
Could be a coolant flow issue.
Whichever it is you will need someone who can look at the software and see what is happening on changover.
As for the missfire, mercs will shut down the cyinder that is missfiring and it will not reset until the ignition has been recycled, which is why it doesn't disappear when you put it back to petrol
Re: Merc engine misfire.
Our mod john_d is also in fife.