Are you shaw that coil order is correct? 1.2 dynamic 2005 mk2 it’s blue badges cable throttle. I can get spark plug boots off the just don’t want to push back on properly I think that could be one of the problems have you any tips on pushing them on as the seam to resist as if they won’t slide down properly. Thanks
Technical Slow picking up
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Slow picking up
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The image of that plug looks like it's been running a little hot/lean, which is sort of backed up by the minus STFT.
I know it's only 1 plug, so we'll come back to that.
The O2 sensor doesn't sniff for O2, the name is a bit misleading.
It creates a small signal voltage based on the heat of the exhaust gas.
Normally a rich mix burn is cooler and a lean mix burn is hotter, so the O2 sends a signal back to the ECU roughly alternating between 0.1v (cooler/richer) and 0.9v (hotter/leaner).
So it appears to have a hot/lean combustion yet the O2 is sensing a rich, or more correctly a cool exhaust gas, so it trying to take fuel away.
There are a few things that cause the lean combustion, but what is causing the exhaust gas to be cooler compared to what we think is a hot/lean burn?
A misfire of some sort will pass unburned hydrocarbons (fuel) and air into the exhaust, lowering it's temperature.
We think it's misfiring, but is that a result of an ignition, ignition timing or compression problem or is it misfiring due to the lean combustion??
A look at all the plugs side by side might point to an individual cyclinder misfire, that would be handy to see.
Is the mix rich due to excess fuel, I think not, combustion is lean but the exhaust is cool as that individual plug doesn't look like it's been running rich or with a misfire while the ECU tries to trim out the fuel, it just looks lean/hot.
So perhaps something else is messing with the O2 sensor to cause it to think it's lean when it isn't, yet it tries to still trim out the fuel.
Something like an exhaust leak would allow exhaust gases to escape and air enter which would cool the O2 sensor to think the fueling is rich, so it tries to take fuel away, causing the lean combustion which it can never trim out.
Before ripping into too much of the car, get someone to hold a rag over the tailpipe and have a look/sniff around the manifold and flexi pipe for leaks.
Also, a good look at all the plugs might identify a single cylinder problem with ignition or compression.
I know it's only 1 plug, so we'll come back to that.
The O2 sensor doesn't sniff for O2, the name is a bit misleading.
It creates a small signal voltage based on the heat of the exhaust gas.
Normally a rich mix burn is cooler and a lean mix burn is hotter, so the O2 sends a signal back to the ECU roughly alternating between 0.1v (cooler/richer) and 0.9v (hotter/leaner).
So it appears to have a hot/lean combustion yet the O2 is sensing a rich, or more correctly a cool exhaust gas, so it trying to take fuel away.
There are a few things that cause the lean combustion, but what is causing the exhaust gas to be cooler compared to what we think is a hot/lean burn?
A misfire of some sort will pass unburned hydrocarbons (fuel) and air into the exhaust, lowering it's temperature.
We think it's misfiring, but is that a result of an ignition, ignition timing or compression problem or is it misfiring due to the lean combustion??
A look at all the plugs side by side might point to an individual cyclinder misfire, that would be handy to see.
Is the mix rich due to excess fuel, I think not, combustion is lean but the exhaust is cool as that individual plug doesn't look like it's been running rich or with a misfire while the ECU tries to trim out the fuel, it just looks lean/hot.
So perhaps something else is messing with the O2 sensor to cause it to think it's lean when it isn't, yet it tries to still trim out the fuel.
Something like an exhaust leak would allow exhaust gases to escape and air enter which would cool the O2 sensor to think the fueling is rich, so it tries to take fuel away, causing the lean combustion which it can never trim out.
Before ripping into too much of the car, get someone to hold a rag over the tailpipe and have a look/sniff around the manifold and flexi pipe for leaks.
Also, a good look at all the plugs might identify a single cylinder problem with ignition or compression.
Yes to order
Your is correct otherwise it would backfire
I have nothing to add over this. Except the plugs being at the back make it slightly slightly awkward. Also look at the angle of the plugs first they fit at a slight angle
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No what I see
I see a slight ash build up on a slightly rich plug
Of course I could be wrong or missing something obvious
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A little too tanny for me.
The point being, it's not a dirty rich looking plug so why is it trimming the fuel out of the mix?
It thinks it's running rich and trying to trim the fuel out, but the plug doesn't look rich or even close to it.
It's looking a little lean yet it's still trying to trim the fuel out, why and what causes that?
The point being, it's not a dirty rich looking plug so why is it trimming the fuel out of the mix?
It thinks it's running rich and trying to trim the fuel out, but the plug doesn't look rich or even close to it.
It's looking a little lean yet it's still trying to trim the fuel out, why and what causes that?
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The plot thickens I will post back when I have some time to take a picture of all the plugs removed I’ve been on about a 50 mile trip today and it did seam to be better then it started to jerk a little when easing off the gas’s not all the time though. You can also feel an occasional misfire as the way I can explain it and slow picking up when excelerating like it’s got a flat spot. Thanks for your time.
Ok thank you I will take another look do you know what the plug gap should be please so I can check mine are correct.Yes to order
Your is correct otherwise it would backfire
I have nothing to add over this. Except the plugs being at the back make it slightly slightly awkward. Also look at the angle of the plugs first they fit at a slight angle
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post cat is pegged at 0.8V mostly which to me is showing it’s not running lean
Pre cat is hard to gauge as we only see rolling number but goes from 0.0V to 0.8V
I said slightly rich might even be to short trips. You posted a picture of a ridiculous rich and wet spark plug it wouldn’t be very nice of me to now post a picture of a very lean spark plug now would it
colour subjective anyhow. Half of the photos on the internet are now wrong as they were on leaded fuel which is completely different. You are in titled to a different opinion to me.
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It’s definitely running rich I would think because my trip out today I actually saw the fuel gauge drop a fare bit as well it done this when I put fuel in as well ok I did drive hard for a minute or 2 in 3rd gear that time but it drop a good way.post cat is pegged at 0.8V mostly which to me is showing it’s not running lean
Pre cat is hard to gauge as we only see rolling number but goes from 0.0V to 0.8V
I said slightly rich might even be to short trips. You posted a picture of a ridiculous rich and wet spark plug it wouldn’t be very nice of me to now post a picture of a very lean spark plug now would it
colour subjective anyhow. Half of the photos on the internet are now wrong as they were on leaded fuel which is completely different. You are in titled to a different opinion to me.
Know Your Engine - Read Your Spark Plugs
Learning how to properly read a spark plug for issues or needed replacement can save you a lot of time and money down the road - let Champion show you how.
Anywhere from 0.8mm to 1.2mm is fine I guess it does vary slightly with manufacturers
I know they start to misfire at just under 2mm
Ok I will give them a check and a bit of a clean. Thanks again.
now you have reseated the spark plug leads do you still get a regular popping from the exhaust
.8 mm is the standard OEM plugs but some of the replacement alternatives are 1mm
.8 mm is the standard OEM plugs but some of the replacement alternatives are 1mm
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Strange we have two Pandas at the moment with fuel trims in the minus
Most of the time the trims go positive.
Not often a good diagnostic aid as an injector not firing at all is slightly positive and a plug not firing at all even less so.
I am assuming the scan tool is reading -100 to +100
And reading the values correctly.
Drivability problems with no codes can be a pain
Plugs
Leads
Coil pack
MAP
Crank sensor
Are all fairly common
As is kangarooing at low speed being the pedal
But in reality there’s probably over 30 possibilities.
We need to gather as much information as we can.
For example if sometime it runs okay but others it stutters it would almost certainly rule out a jumped timing belt.
Coasting, accelerating, hot or cold engine, starts fine and goes worse, starts bad gets better, high revs, low revs and so on, are all clues
Most of the time the trims go positive.
Not often a good diagnostic aid as an injector not firing at all is slightly positive and a plug not firing at all even less so.
I am assuming the scan tool is reading -100 to +100
And reading the values correctly.
Drivability problems with no codes can be a pain
Plugs
Leads
Coil pack
MAP
Crank sensor
Are all fairly common
As is kangarooing at low speed being the pedal
But in reality there’s probably over 30 possibilities.
We need to gather as much information as we can.
For example if sometime it runs okay but others it stutters it would almost certainly rule out a jumped timing belt.
Coasting, accelerating, hot or cold engine, starts fine and goes worse, starts bad gets better, high revs, low revs and so on, are all clues
Nice quick test
Let’s see if we have an exhaust leak pre CAT
Put your hand over the exhaust pipe at the back of the car
Does the pressure build up
If it does good we can move on. If it’s leaking where will have to be investigated
Let’s see if we have an exhaust leak pre CAT
Put your hand over the exhaust pipe at the back of the car
Does the pressure build up
If it does good we can move on. If it’s leaking where will have to be investigated
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post cat is pegged at 0.8V mostly which to me is showing it’s not running lean
Pre cat is hard to gauge as we only see rolling number but goes from 0.0V to 0.8V
I said slightly rich might even be to short trips. You posted a picture of a ridiculous rich and wet spark plug it wouldn’t be very nice of me to now post a picture of a very lean spark plug now would it
colour subjective anyhow. Half of the photos on the internet are now wrong as they were on leaded fuel which is completely different. You are in titled to a different opinion to me.
Know Your Engine - Read Your Spark Plugs
Learning how to properly read a spark plug for issues or needed replacement can save you a lot of time and money down the road - let Champion show you how.
The pre cat sensor is only showing the electrical signal generated.
Yes, it should be a reflection of what is happeneing in the combustion chambers, but if there's a leak it won't be a true reflection as it's not getting an unadulterated reading of the exhaust gas from the combustion chambers.
What you end up with is low voltage sent back to the ECU so that thinks it's rich, then it tries to trim the fuel out.
So now you're left with a O2 reporting a rich mix, a minus fuel trim yet you get a lean combustion.
There are of course other reasons to end up with the same condition, but it's best to start on some firm ground and check the obvious.
It's an old car, it's not had much use and we know the flexi pipes on these tend to blow sooner rather than later.
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You might need to click on the plug image on the left.
It opens up to show a lean, rich and optimal plug colourings.
Which of these is closest to the OP's plug (single plug image on the right).
It opens up to show a lean, rich and optimal plug colourings.
Which of these is closest to the OP's plug (single plug image on the right).
Are you sure that pictures right looks to me like two of the headings are the wrong way round
Here a chart from the OEM plug supplier
And a plug out of an engine with a confirmed lean condition
Tries to trim fuel out sounds wrong
With a cracked exhaust manifold the O2 sensor will see a lean condition so the ECU add more fuel. Surly ?
Minus fuel trim not sure I understand aren’t we adding fuel for the lean condition seen by the O2
It’s more complicated than this as it depends where it’s leaking. But as a rule of thumb plus trims and rich running
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Your image in post 57 looks about right for a normal plug.
When they a bit too tanny coloured and the little bit of sooty carbon that is normally found on a plugs turns to ash, that's a sign it's a little hot.
You need higher temps to turn soot to ash. (the leaner the higher the temp).
Modern cars tend to be cleaner and more efficient as they tend to burn their fuel more efficiently, so some greyish tan colour seems to be more normal these days.
Like I wrote earlier, the O2 sensor is badly named, they are also commonly called Lambda sensors (electrical conductance).
They don't sense oxygen, they work off heat.
They convert heat in the exhaust gas to an electrical signal and send that back to the ECU.
The less heat the lower the signal which the ECU thinks is rich.
The higher the heat the higher the signal which the ECU thinks is lean.
More oxygen in combustion will cause a lean/high heat reading, but not unburned oxygen in the exhaust, that will just lower the temps of the gas.
Normally the sensors signal will switch at idle, up and down between 0.1v and 0.9v in closed loop.
(modern O2 sensors have a heater element, this allows the ECU to select closed loop much sooner than waiting for the sensor to naturally heat up to operating temp, so tend to be cleaner and more efficient)
The mid point between these two signals is an indication of what is happening overall.
Ideally it should average out around 0.45v or so but you can take whatever is reported and find the mid point between the two to see what the O2 thinks is happeneing with the temp of the exhaust gas and thus the fueling strategy the ECU is likely to take.
Mid point lower than ideal 0.45v, the ECU thinks combustion is rich, so the ECU takes fuel away.
Mid point higher than ideal 0.45v, the ECU thinks it's lean, so the ECU adds fuel.
Notice I write "normally" and "thinks".
If anything interferes with the temp of exhaust gas, that interferes with the signal being sent back to the ECU that works out the fueling.
So anything that lowers the heat in the exhaust, say some of the gas escapes or the exhaust draws in air near the sensor, it will cause the O2 to produce a lower electrical signal, the ECU will think it's rich due to the lower elctrical signal and take fuel away.
Oppositely, if something interferes with the exhaust gas to make them hotter, like a intake leak drawing in unmetered air, the O2 would produce a higher voltage and the ECU would presume it's lean and add fuel.
If the engine was really running rich, we would see the same effect on the O2 sensor and the ECU taking fuel away, but we should see some evidence of that rich combustion on the plugs. This plug evidence might not be overlly obvious, it depends on the state of the problem and how long it's been happeneing.
I know we haven't seen all of the the plugs yet and haven't really a clue how long the problem has been happening but that single plug doesn't look like it's been running anything like rich.
It appears there is a mismatch between combustion and what the O2 is reporting from the exhaust gas temps.
So when testing and trying to trace these types of faults and issues it's best to confirm that the phyical things like the exhaust are in good condition first, so the data you are reading with diagnostic tools is, for want of a better word, trustable.
Interestingly, some cars have problems with the MOT Lambda test.
The Lambda test machine is more sophisticated sensor similar to the O2, just further down the exhaust system at the tailpipe.
Some cars exhausts cause problems with this test, not because of an exhaust leak but because there is air getting back into the tailpipe and confusing the machine.
There are some posts about this on the forum with some Pandas, I had it when I took my 4x4 TA to it's first MOT and the Clio 182 was notorious for the problem. The trick is to stick a rag up the exhaust so the machine had more available gas to test, but obviously the MOT tester isnt influencing the engines fueling.
When they a bit too tanny coloured and the little bit of sooty carbon that is normally found on a plugs turns to ash, that's a sign it's a little hot.
You need higher temps to turn soot to ash. (the leaner the higher the temp).
Modern cars tend to be cleaner and more efficient as they tend to burn their fuel more efficiently, so some greyish tan colour seems to be more normal these days.
Like I wrote earlier, the O2 sensor is badly named, they are also commonly called Lambda sensors (electrical conductance).
They don't sense oxygen, they work off heat.
They convert heat in the exhaust gas to an electrical signal and send that back to the ECU.
The less heat the lower the signal which the ECU thinks is rich.
The higher the heat the higher the signal which the ECU thinks is lean.
More oxygen in combustion will cause a lean/high heat reading, but not unburned oxygen in the exhaust, that will just lower the temps of the gas.
Normally the sensors signal will switch at idle, up and down between 0.1v and 0.9v in closed loop.
(modern O2 sensors have a heater element, this allows the ECU to select closed loop much sooner than waiting for the sensor to naturally heat up to operating temp, so tend to be cleaner and more efficient)
The mid point between these two signals is an indication of what is happening overall.
Ideally it should average out around 0.45v or so but you can take whatever is reported and find the mid point between the two to see what the O2 thinks is happeneing with the temp of the exhaust gas and thus the fueling strategy the ECU is likely to take.
Mid point lower than ideal 0.45v, the ECU thinks combustion is rich, so the ECU takes fuel away.
Mid point higher than ideal 0.45v, the ECU thinks it's lean, so the ECU adds fuel.
Notice I write "normally" and "thinks".
If anything interferes with the temp of exhaust gas, that interferes with the signal being sent back to the ECU that works out the fueling.
So anything that lowers the heat in the exhaust, say some of the gas escapes or the exhaust draws in air near the sensor, it will cause the O2 to produce a lower electrical signal, the ECU will think it's rich due to the lower elctrical signal and take fuel away.
Oppositely, if something interferes with the exhaust gas to make them hotter, like a intake leak drawing in unmetered air, the O2 would produce a higher voltage and the ECU would presume it's lean and add fuel.
If the engine was really running rich, we would see the same effect on the O2 sensor and the ECU taking fuel away, but we should see some evidence of that rich combustion on the plugs. This plug evidence might not be overlly obvious, it depends on the state of the problem and how long it's been happeneing.
I know we haven't seen all of the the plugs yet and haven't really a clue how long the problem has been happening but that single plug doesn't look like it's been running anything like rich.
It appears there is a mismatch between combustion and what the O2 is reporting from the exhaust gas temps.
So when testing and trying to trace these types of faults and issues it's best to confirm that the phyical things like the exhaust are in good condition first, so the data you are reading with diagnostic tools is, for want of a better word, trustable.
Interestingly, some cars have problems with the MOT Lambda test.
The Lambda test machine is more sophisticated sensor similar to the O2, just further down the exhaust system at the tailpipe.
Some cars exhausts cause problems with this test, not because of an exhaust leak but because there is air getting back into the tailpipe and confusing the machine.
There are some posts about this on the forum with some Pandas, I had it when I took my 4x4 TA to it's first MOT and the Clio 182 was notorious for the problem. The trick is to stick a rag up the exhaust so the machine had more available gas to test, but obviously the MOT tester isnt influencing the engines fueling.
1 Lambda is a Greek letter used as shorthand to represent the perfect stoichiometric mixture.
Really
The centre insulator is fairly clean, white or white glazed If the car is running lean or lean and overheating
This is the original poster plug. I would prefer to see all 4 but from this there is no evidence of running lean from the information
With a post CAT sensor mostly showing a rich 0.8V
And pre CAT also going to 0.8V
This isn’t indicating a lean condition either
This is also not an indication of air entering the exhaust
Drivability issues without an error code can be tricky to narrow down
Without making the treads overly long.
We have a difference of opinion that’s fine. Arguing about does not help the original poster we need to diagnose the problem. You maybe right, I maybe right
I asked the original poster to put their hand over the exhaust mainly to double check so not solely relying on the plug and sensor data. I don’t expect an exhaust manifold leak but it’s a 1 minute check
Someone else has suggested the inlet manifold gasket
All of which is no getting lost in bickering and explanations on how an engine runs
Fuel trims pegged negative is fairly rare and we have two at the moment that need sorting. This one has long term fuel trims of -100
Misfire ignition drives them positive
Misfire injector not firing positive
Exhaust leak pre CAT positive
Inlet manifold leak positive
Restrictive air negative
Faulty injector negative or positive
Faulty O2 negative or positive
Fuel regulator negative or positive
Faulty MAP negative or positive
Fault EVAP negative
And loads more I have missed no doubt
