Discussion
Hi
Monaro VXR 2005 LS2, having trouble with rough running causing the gear lever to shake and a essitation for engine revs to pick up cleanly when engine under load under quick acceleration. After a few seconds of this car then picks up and runs fine at higher revs.
Once this happens when idle, there is occations when raising the revs the engine seems to miss fire until around 2-3000 rpm but not always.
Leave car untile cold and start journey no problems for a while then above starts again.
Put fault finder OB2 on and even when problem is there, there is no codes coming up or any misfires regestering.
Real head scratcher.
Any help would be thankfully recieved.
Ade
Monaro VXR 2005 LS2, having trouble with rough running causing the gear lever to shake and a essitation for engine revs to pick up cleanly when engine under load under quick acceleration. After a few seconds of this car then picks up and runs fine at higher revs.
Once this happens when idle, there is occations when raising the revs the engine seems to miss fire until around 2-3000 rpm but not always.
Leave car untile cold and start journey no problems for a while then above starts again.
Put fault finder OB2 on and even when problem is there, there is no codes coming up or any misfires regestering.
Real head scratcher.
Any help would be thankfully recieved.
Ade
Hi Ade,
As above, my first thoughts are plugs and or plug leads. They are the easy things to eliminate first.
After that it's an expensive guessing game.
It's always difficult without fault codes, but.....if no codes are being shown then all the sensors are likely to be OK.
John
As above, my first thoughts are plugs and or plug leads. They are the easy things to eliminate first.
After that it's an expensive guessing game.
It's always difficult without fault codes, but.....if no codes are being shown then all the sensors are likely to be OK.
John
Edited by mfp4073 on Tuesday 28th July 14:40
stevieturbo said:
It really isnt difficult.
Look at the plugs, look at the leads.
When it's running, one by one unplug an injector to see if you can identify which cylinder or cylinders are not firing.
And take it from there.
Wtll check all leads and plugs as others too mention, on tick over the engine is smooth so unpluging leads one at a time will not isolate faulty cylinder as I see it.Look at the plugs, look at the leads.
When it's running, one by one unplug an injector to see if you can identify which cylinder or cylinders are not firing.
And take it from there.
Ade
Ade,
Just a couple of basic no cost checks before spending any cash.
You have had your car for a number of years now, so have you changed the plugs yet.
I believe you will get at least 50,000 miles out of the factory iridium plugs before you need to change them.
However If you have Copper plugs fitted they don't last very long at all and may need changing.
The factory plug leads generally seperate and fail when they have been removed a couple of times, so they will need a good check over.
The individual coil packs should be fine as they are usually very reliable.
I suppose if you could get someone to rev the car from tickover until it starts to run rough, then you could remove each plug lead individually and identify the problem cylinder. Obviously watch out for electric shocks as you would no doubt get quite a jolt
As mentioned previously try disconnecting the fuel injector wiring which might be less painful!!!
John
Just a couple of basic no cost checks before spending any cash.
You have had your car for a number of years now, so have you changed the plugs yet.
I believe you will get at least 50,000 miles out of the factory iridium plugs before you need to change them.
However If you have Copper plugs fitted they don't last very long at all and may need changing.
The factory plug leads generally seperate and fail when they have been removed a couple of times, so they will need a good check over.
The individual coil packs should be fine as they are usually very reliable.
I suppose if you could get someone to rev the car from tickover until it starts to run rough, then you could remove each plug lead individually and identify the problem cylinder. Obviously watch out for electric shocks as you would no doubt get quite a jolt
As mentioned previously try disconnecting the fuel injector wiring which might be less painful!!!
John
Edited by mfp4073 on Tuesday 28th July 23:22
[quote=mfp4073]Ade,
Just a couple of basic no cost checks before spending any cash.
You have had your car for a number of years now, so have you changed the plugs yet.
I believe you will get at least 50,000 miles out of the factory iridium plugs before you need to change them.
However If you have Copper plugs fitted they don't last very long at all and may need changing.
The factory plug leads generally seperate and fail when they have been removed a couple of times, so they will need a good check over.
The individual coil packs should be fine as they are usually very reliable.
I suppose if you could get someone to rev the car from tickover until it starts to run rough, then you could remove each plug lead individually and identify the problem cylinder. Obviously watch out for electric shocks as you would no doubt get quite a jolt
As mentioned previously try disconnecting the fuel injector wiring which might be less painful!!!
John
John the iridium plugs have only been in 20,000 mls and also the Magnicore leads.
I am starting by putting a set of known working spare leads on, then see if that makes a diference, then if so ,one by one put the newer leads back on untile I find the dodgy one.
If no difference will remove each plug and examine and change.
Maff was cleaned not so long ago but will clean again.
Keep you all up to date on progress.
Thanks all
Ade
Just a couple of basic no cost checks before spending any cash.
You have had your car for a number of years now, so have you changed the plugs yet.
I believe you will get at least 50,000 miles out of the factory iridium plugs before you need to change them.
However If you have Copper plugs fitted they don't last very long at all and may need changing.
The factory plug leads generally seperate and fail when they have been removed a couple of times, so they will need a good check over.
The individual coil packs should be fine as they are usually very reliable.
I suppose if you could get someone to rev the car from tickover until it starts to run rough, then you could remove each plug lead individually and identify the problem cylinder. Obviously watch out for electric shocks as you would no doubt get quite a jolt
As mentioned previously try disconnecting the fuel injector wiring which might be less painful!!!
John
Edited by mfp4073 on Tuesday 28th July 23:22
[/quoteJohn the iridium plugs have only been in 20,000 mls and also the Magnicore leads.
I am starting by putting a set of known working spare leads on, then see if that makes a diference, then if so ,one by one put the newer leads back on untile I find the dodgy one.
If no difference will remove each plug and examine and change.
Maff was cleaned not so long ago but will clean again.
Keep you all up to date on progress.
Thanks all
Ade
mfp4073 said:
Ade,
I've just had a thought!!!!
Didn't the LS2 have some issues with the throttle bodies? I don't recall the symptoms but it's something else to consider. Hopefully someone on here may remember.
John
Yes indeed but it normally (always?) throws a code and plonks it in limp.I've just had a thought!!!!
Didn't the LS2 have some issues with the throttle bodies? I don't recall the symptoms but it's something else to consider. Hopefully someone on here may remember.
John
Hi guys
Problem solved, it is one of the four spark plugs on passenger side bank of cylinders.
Changed all four for known working plugs, and engine runs fine pulls from 1,000 rpm in 6th, no hesitation and thats as much load can be applied. So even though the NGK iridium plugs have only done 20,000 mls I am putting a full new set in.
Not trusting any of the others thats in engine now.
Funny thing is. that each of the four plugs removed looked fine, and the thing I still cannot understand is when car was stood the engine would easy rev to 3,000rpm and not miss a beat, but drive with some load and the engine would shake crazy.
Any one can put any light on this would probably help for same thing happening to any one else,
Thanks for all your input guys
Ade
Problem solved, it is one of the four spark plugs on passenger side bank of cylinders.
Changed all four for known working plugs, and engine runs fine pulls from 1,000 rpm in 6th, no hesitation and thats as much load can be applied. So even though the NGK iridium plugs have only done 20,000 mls I am putting a full new set in.
Not trusting any of the others thats in engine now.
Funny thing is. that each of the four plugs removed looked fine, and the thing I still cannot understand is when car was stood the engine would easy rev to 3,000rpm and not miss a beat, but drive with some load and the engine would shake crazy.
Any one can put any light on this would probably help for same thing happening to any one else,
Thanks for all your input guys
Ade
Glad you got the job sorted, and it was a relatively easy fix.
The only thing I can think of is maybe you had a cracked insulator which was arcing out under load causing a misfire.
I suppose it's even possible one of the plugs may have been faulty from new and eventually broke down over time.
John
The only thing I can think of is maybe you had a cracked insulator which was arcing out under load causing a misfire.
I suppose it's even possible one of the plugs may have been faulty from new and eventually broke down over time.
John
mfp4073 said:
Glad you got the job sorted, and it was a relatively easy fix.
The only thing I can think of is maybe you had a cracked insulator which was arcing out under load causing a misfire.
I suppose it's even possible one of the plugs may have been faulty from new and eventually broke down over time.
John
Long time ago I had a plug which would spark outside but not when under pressure in the cylinder. Much head scratching till I worked that out!The only thing I can think of is maybe you had a cracked insulator which was arcing out under load causing a misfire.
I suppose it's even possible one of the plugs may have been faulty from new and eventually broke down over time.
John
Good test for ignition - go up a hill in high gear and low RPM.
Ignition is under less stress at high RPM because the ignition advance is firing it under low compression conditions.
Ignition is under less stress when accelerating due to richer fuel conditions.
Ignition is under max stress when at low speed (spark is close to TDC), and under load (compression is higher), and without accelerating (fuel is less rich).
This is when ignition problems will tend to show up, and usually differentiate from fuelling issues.
I use this test frequently when the fault codes are inconclusive, and will work for any SI engine.
Ignition is under less stress at high RPM because the ignition advance is firing it under low compression conditions.
Ignition is under less stress when accelerating due to richer fuel conditions.
Ignition is under max stress when at low speed (spark is close to TDC), and under load (compression is higher), and without accelerating (fuel is less rich).
This is when ignition problems will tend to show up, and usually differentiate from fuelling issues.
I use this test frequently when the fault codes are inconclusive, and will work for any SI engine.
bearman68 said:
Good test for ignition - go up a hill in high gear and low RPM.
Ignition is under less stress at high RPM because the ignition advance is firing it under low compression conditions.
Ignition is under less stress when accelerating due to richer fuel conditions.
Ignition is under max stress when at low speed (spark is close to TDC), and under load (compression is higher), and without accelerating (fuel is less rich).
This is when ignition problems will tend to show up, and usually differentiate from fuelling issues.
I use this test frequently when the fault codes are inconclusive, and will work for any SI engine.
Thats why my problem only occured under load, thanks for that info.Ignition is under less stress at high RPM because the ignition advance is firing it under low compression conditions.
Ignition is under less stress when accelerating due to richer fuel conditions.
Ignition is under max stress when at low speed (spark is close to TDC), and under load (compression is higher), and without accelerating (fuel is less rich).
This is when ignition problems will tend to show up, and usually differentiate from fuelling issues.
I use this test frequently when the fault codes are inconclusive, and will work for any SI engine.
Ade
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