Plug colour variation?
Discussion
Hi All- I’ve noticed that while most of the plugs are a good colour, 3 of them seem to have more of a darker colour as if the mixture was richer.
They didn’t all come from the same bank and I’m wondering if it’s time to get the injectors cleaned? Or should I just ignore it?
There are no other running faults- it goes well and has only done just over 40k miles (‘98 400).
Many thanks for your ideas.
They didn’t all come from the same bank and I’m wondering if it’s time to get the injectors cleaned? Or should I just ignore it?
There are no other running faults- it goes well and has only done just over 40k miles (‘98 400).
Many thanks for your ideas.
Depending on your skill level it is not difficult to move the injectors around to see if the problem moves with the injectors or stays with the cylinder.
On the other hand it may well be worthwhile just getting them serviced rather than messing about.
They should come back to you with a report on before and after performance.
Steve
On the other hand it may well be worthwhile just getting them serviced rather than messing about.
They should come back to you with a report on before and after performance.
Steve
I've had my injectors done by Injectortune on my last 2 TVRs:
http://www.injectortune.co.uk/Injector_Cleaning.ht...
Good service with a performance report, and a definite improvement on running afterwards. Not specifically more power, but easier cold starting and smoother idle.
http://www.injectortune.co.uk/Injector_Cleaning.ht...
Good service with a performance report, and a definite improvement on running afterwards. Not specifically more power, but easier cold starting and smoother idle.
blitzracing said:
Fouled injectors show up as uneven plug colour across the insulator tip. It caused by the fuel remaining in larger droplets as it enters the combustion chamber and it washes the carbon of the plug on the inlet valve side before it burns.
Yes I’ve heard that before and a very good tip 
blitzracing said:
Fouled injectors show up as uneven plug colour across the insulator tip.
Indeed - this is what got me thinking that the injectors were in need of a bit of surgery - 3 of the 8 plugs were a bit carbon fouled.At least I don't need to worry about changing the plug heat range (from a 7) - or have I risked opening another can of worms......
Do consider there is more than a fuel injector flow or effective spray pattern/atomisation that can influence a variation in plug colour across cylinders. 
You need to consider the colour of a plug tells you a huge amount about the air fuel ratio and quality of the combustion activity in that cylinder, but always remember what you're observing is really just a symptom of something else so my advice would be to broaden your thinking beyond just injectors.
Lets look at the top seven points to consider, these are not in order of likeliness, indeed I have put injectors first as the truth is they have less of an impact on plug colour variation than say ignition issues, an induction leak or cam wear... so I'd move on from this point fairly quickly if I was you
1. Injectors - possible but as I say less of an influencer than my other listed points of consideration
2. Poor engine earthing - This came as standard with every Chimaera and Griffith built and is probably the most overlooked point on our cars when diagnosing a myriad of engine behavior issues
3. Valve seat recession, a partially stuck valve or broken rocker - Can happen but not at the top of my list in this case
4. Cam shaft wear - Very common on the Rover V8 and is very often cylinder specific
5. Cylinder specific ignition issues - Extremely common on TVR Chimaeras and Griffiths due to the exhaust manifold design
6. Exhaust leak at a header pipe - Very common, listen for the telltale tick
7. Inlet manifold leak specific to one inlet gasket - Always something to check as this will weaken the mixture on a specific cylinder
Point 1 - The Chimaera and Griffith were fitted with disc type injectors which are very quiet but very out of date in the world of fuel injector design and technology. One option to update is to find a set of Siemens injectors from a Vauxhall Vectra and have them cleaned and flow matched, these Vectra injectors are the far better and now universally adopted pintle type design. Vectra injectors are also the correct fitment type and impedance so are a straight drop in replacement for the old original Lucas disc type dribblers, they are also very common so cheap to buy, what you'll find is you can buy a set of Vectra injectors that offer far better fuel atomisation and have them reconditioned for the same price as having your old Lucas injectors serviced which to be honest is a no-brainer. I did this 8 years ago and they've been perfect, he Vectra injector swap is a well trodden and proven path in RV8 TVR circles.
Point 2 - TVR did not earth the engine well at all, do not underestimate this as it can very often cause all sorts of running issues with engine management and ignition systems. To help the issue that is so common of fiberglass bodied cars that do not benefit from a steel moncoque shell which offers far superior earthing, simply add to the original thin single engine earth cable used by TVR by running a new heavier gauge cable directly from a stout bolt on the block to the battery negative terminal. This one simple addition can often deliver fantastic improvements in ignition strength, injector duration consistency, AFR stability, engine sensor accuracy, oil pressure readings, drivability, throttle response, fuel economy, idle quality and a host of other benefits.
Points 3 & 4 - A compression test (wet & dry) and the correct use/reading of a vacuum gauge are the correct methods used to diagnose the mechanical elements listed against this point. If you are not confident to do so yourself it's well worth paying an experienced professional to complete these tests as they will tell you a huge amount about the condition of your engine internals.
Point 5 - The ignition elements covered in point 5 are probably the most common causes of poor running and differences in plug colour on Chimaera and Griffs, this has a lot to do with heat the TVR manifolds and retarded emissions based ignition timing both of which work very effectively to put HT leads, their plug boots and even the spark plugs themselves under far greater stress than they were intended to tolerate. You can test your HT leads, the plug extenders used by TVR and even the plugs with a simple Ohm meter. Failing HT leads, plug extenders, and even the inappropriate and too cold B7ECS plugs chosen by TVR can all very often give poor combustion results specific to a cylinder on TVR Chimaeras and Griffiths.
Points 6 & 7 - Induction leaks are a classic influencer of plug colour, if 7 of your plugs display a good colour but the eighth is whiter than the rest suspect an induction leak on anything unique to that cylinder on the inlet side such as a failed manifold gasket on the specific inlet port relating to the same cylinder. Exhaust leaks at the header pipe are a perennial problem with our cars and while less impactful on plug colour they can influence cylinder specific combustion events so can also be an influencer in this respect
Going back to the big one for me which is ignition, if you're still running the inappropriate B7ECS plugs replacing them with an extended electrode NGK plug in the hotter 6 heat rating will give immediate benefits. In day to day driving on the road the too cold rated B7ECS plugs specified by TVR never reach their self cleaning temperature causing them to foul and show carbon which in turn contributes to small occasional misfires which tend to plague our cars.
Also check the plug is secure but not over tight in the cylinder head as if loose will allow combustion gasses to pass up the plug leaving carbon deposits on the threads. Not only will you be wasting those valuable compression gasses but the deposits they leave behind on the plug thread will cause poor earthing of the plug itself which in turn will give you a compromised spark and so poor combustion. Always use new compression washers on your plugs after removing and inspecting them, the compression washer assists in setting the correct torque of the plug, stops premature loosening of the plug, and acts as a compression seal. Spark plug compression washers are a one time fit component, once you've pulled a plug out you need to fit new compression washers which are cheap and readily available.
Never use copper-clip or other anti-seize greases on the spark plug threads, this was good practice over 30 years ago before NGK developed special thread coatings that made the use of copper-slip ect obsolete overnight. Anti-seize greases only serve to interfere with the torque setting when you set the plug in the head, the now unnecessary anti-seize grease also does nothing to aid effective earthing of the plug which as mentioned earlier is often poor in our TVRs.
Finally if you're still running the original plug extenders these are well known to give trouble, I recommend removing them entirely and protecting your HT lead spark plug boots using heat protective socks. Better HT leads are also available, I favor MSD Superconductors, others use ACCEL Ceramic booted leads to help with the burnt boot issue while also replacing their lead set at the same time.
So you see, there's a lot more to it than injectors, the real answer is not to just focus on your injectors but to take an holistic approach to resolving the cylinder specific combustion anomalies you are observing when you view your spark plug colour variation.
I'm sorry to say there is no one single silver bullet solution that so many seek of these type of forums, the truth is the solution lies somewhere in all the above points and most likely will be the accumulated consiquence of more than one of my suggestions. What I can tell you is there are very real rewards to be had by just studying the basics of an internal combustion engine and applying a systematic approach of well considered and holistic diagnosis.
Key tools in your armory of diagnostic equipment should be the following:
1. A good multimeter
2. A vacuum gauge, study how to read it and what it's telling you
3. A short length of garden hose or fuel hose to act as a listening device to check for exhaust or induction leaks
4. A compression tester
5. An oscilloscope for testing high tension KV ect, an oscilloscope is invaluable for detecting misfires and other ignition related maladies. I was trained on a Sun Tuner machine the size of industrial washing machine, these days you can buy an automotive oscilloscope the size of a paper back book for £75 that plugs into your laptop
If you don't have all that kit or are not confident how to use it find someone who specializes in engine diagnostic work but find someone with grey hair who's been doing it all their life because the younger guys wont have a clue how to do all the fundamental checks on an older car like a Chimaera and all they will want to do is plug their fault code reader in which likely won't work on the 14CUX ECU anyway.
Hope all this helps?
You need to consider the colour of a plug tells you a huge amount about the air fuel ratio and quality of the combustion activity in that cylinder, but always remember what you're observing is really just a symptom of something else so my advice would be to broaden your thinking beyond just injectors.
Lets look at the top seven points to consider, these are not in order of likeliness, indeed I have put injectors first as the truth is they have less of an impact on plug colour variation than say ignition issues, an induction leak or cam wear... so I'd move on from this point fairly quickly if I was you
1. Injectors - possible but as I say less of an influencer than my other listed points of consideration
2. Poor engine earthing - This came as standard with every Chimaera and Griffith built and is probably the most overlooked point on our cars when diagnosing a myriad of engine behavior issues
3. Valve seat recession, a partially stuck valve or broken rocker - Can happen but not at the top of my list in this case
4. Cam shaft wear - Very common on the Rover V8 and is very often cylinder specific
5. Cylinder specific ignition issues - Extremely common on TVR Chimaeras and Griffiths due to the exhaust manifold design
6. Exhaust leak at a header pipe - Very common, listen for the telltale tick
7. Inlet manifold leak specific to one inlet gasket - Always something to check as this will weaken the mixture on a specific cylinder
Point 1 - The Chimaera and Griffith were fitted with disc type injectors which are very quiet but very out of date in the world of fuel injector design and technology. One option to update is to find a set of Siemens injectors from a Vauxhall Vectra and have them cleaned and flow matched, these Vectra injectors are the far better and now universally adopted pintle type design. Vectra injectors are also the correct fitment type and impedance so are a straight drop in replacement for the old original Lucas disc type dribblers, they are also very common so cheap to buy, what you'll find is you can buy a set of Vectra injectors that offer far better fuel atomisation and have them reconditioned for the same price as having your old Lucas injectors serviced which to be honest is a no-brainer. I did this 8 years ago and they've been perfect, he Vectra injector swap is a well trodden and proven path in RV8 TVR circles.
Point 2 - TVR did not earth the engine well at all, do not underestimate this as it can very often cause all sorts of running issues with engine management and ignition systems. To help the issue that is so common of fiberglass bodied cars that do not benefit from a steel moncoque shell which offers far superior earthing, simply add to the original thin single engine earth cable used by TVR by running a new heavier gauge cable directly from a stout bolt on the block to the battery negative terminal. This one simple addition can often deliver fantastic improvements in ignition strength, injector duration consistency, AFR stability, engine sensor accuracy, oil pressure readings, drivability, throttle response, fuel economy, idle quality and a host of other benefits.
Points 3 & 4 - A compression test (wet & dry) and the correct use/reading of a vacuum gauge are the correct methods used to diagnose the mechanical elements listed against this point. If you are not confident to do so yourself it's well worth paying an experienced professional to complete these tests as they will tell you a huge amount about the condition of your engine internals.
Point 5 - The ignition elements covered in point 5 are probably the most common causes of poor running and differences in plug colour on Chimaera and Griffs, this has a lot to do with heat the TVR manifolds and retarded emissions based ignition timing both of which work very effectively to put HT leads, their plug boots and even the spark plugs themselves under far greater stress than they were intended to tolerate. You can test your HT leads, the plug extenders used by TVR and even the plugs with a simple Ohm meter. Failing HT leads, plug extenders, and even the inappropriate and too cold B7ECS plugs chosen by TVR can all very often give poor combustion results specific to a cylinder on TVR Chimaeras and Griffiths.
Points 6 & 7 - Induction leaks are a classic influencer of plug colour, if 7 of your plugs display a good colour but the eighth is whiter than the rest suspect an induction leak on anything unique to that cylinder on the inlet side such as a failed manifold gasket on the specific inlet port relating to the same cylinder. Exhaust leaks at the header pipe are a perennial problem with our cars and while less impactful on plug colour they can influence cylinder specific combustion events so can also be an influencer in this respect
Going back to the big one for me which is ignition, if you're still running the inappropriate B7ECS plugs replacing them with an extended electrode NGK plug in the hotter 6 heat rating will give immediate benefits. In day to day driving on the road the too cold rated B7ECS plugs specified by TVR never reach their self cleaning temperature causing them to foul and show carbon which in turn contributes to small occasional misfires which tend to plague our cars.
Also check the plug is secure but not over tight in the cylinder head as if loose will allow combustion gasses to pass up the plug leaving carbon deposits on the threads. Not only will you be wasting those valuable compression gasses but the deposits they leave behind on the plug thread will cause poor earthing of the plug itself which in turn will give you a compromised spark and so poor combustion. Always use new compression washers on your plugs after removing and inspecting them, the compression washer assists in setting the correct torque of the plug, stops premature loosening of the plug, and acts as a compression seal. Spark plug compression washers are a one time fit component, once you've pulled a plug out you need to fit new compression washers which are cheap and readily available.
Never use copper-clip or other anti-seize greases on the spark plug threads, this was good practice over 30 years ago before NGK developed special thread coatings that made the use of copper-slip ect obsolete overnight. Anti-seize greases only serve to interfere with the torque setting when you set the plug in the head, the now unnecessary anti-seize grease also does nothing to aid effective earthing of the plug which as mentioned earlier is often poor in our TVRs.
Finally if you're still running the original plug extenders these are well known to give trouble, I recommend removing them entirely and protecting your HT lead spark plug boots using heat protective socks. Better HT leads are also available, I favor MSD Superconductors, others use ACCEL Ceramic booted leads to help with the burnt boot issue while also replacing their lead set at the same time.
So you see, there's a lot more to it than injectors, the real answer is not to just focus on your injectors but to take an holistic approach to resolving the cylinder specific combustion anomalies you are observing when you view your spark plug colour variation.
I'm sorry to say there is no one single silver bullet solution that so many seek of these type of forums, the truth is the solution lies somewhere in all the above points and most likely will be the accumulated consiquence of more than one of my suggestions. What I can tell you is there are very real rewards to be had by just studying the basics of an internal combustion engine and applying a systematic approach of well considered and holistic diagnosis.
Key tools in your armory of diagnostic equipment should be the following:
1. A good multimeter
2. A vacuum gauge, study how to read it and what it's telling you
3. A short length of garden hose or fuel hose to act as a listening device to check for exhaust or induction leaks
4. A compression tester
5. An oscilloscope for testing high tension KV ect, an oscilloscope is invaluable for detecting misfires and other ignition related maladies. I was trained on a Sun Tuner machine the size of industrial washing machine, these days you can buy an automotive oscilloscope the size of a paper back book for £75 that plugs into your laptop
If you don't have all that kit or are not confident how to use it find someone who specializes in engine diagnostic work but find someone with grey hair who's been doing it all their life because the younger guys wont have a clue how to do all the fundamental checks on an older car like a Chimaera and all they will want to do is plug their fault code reader in which likely won't work on the 14CUX ECU anyway.
Hope all this helps?
Thank-you for your very detailed fault diagnosis.
You are correct of course, given the list of possible culprits, it is going to be a process of elimination.
Having already removed the fuel rail in the course of a valley gasket swap, and for the cost of servicing the injectors, this course of action seems to make sense. At least if the report comes back and details that 3 of them needed some additional surgery, this might be a good pointer(?).
The car doesn’t suffer from a (detectable) miss-fire, only an occasional low-rev/speed ‘shunting’ when cold (like most Chim’s).
The HT leads are new(ish) and despite the wave of opinion against the B7ECS plugs, 5 show a good colour (and this was after an extensive idling period, whilst I checked the fan operation with an I/R thermometer). Maybe, if I’d just switched the engine off after the quick blast all plugs might’ve shown a good colour?
However, I am toying with the idea of changing to BPR7ES – ‘R’ because I have also invested in some Lava Rock Socks to ditch the extenders (which might also be contributing to the slight fouling of the (3) plugs, - although there’s no obvious damage on any of them).
I’ve not done a compression test as yet (but I do have a tester).
With regards to cam wear – an RV8 Achilles heel alright– I understand that some lobes are more prone to wear than others. I’ll check this against the plugs I’ve pulled (I’ve kept their cylinder numbers marked).
I’ll investigate the valve gear further in the course of the VG swap.
Otherwise, The engine seems in good health, only uses about 100ml of oil per 1k miles (but most of this seems to be coming from the valley gasket/sump joint), and doesn’t use any coolant. It always starts first time (at least since I fitted the David Beer hot-start relay), and only gets a bit fluffy if you touch the throttle immediately after starting when it’s very cold, but this soon clears.
I like the idea of an additional engine earth. I’ve fitted these in the past to get over a myriad of issues not related to GRP bodies, but due to general loom degradation and is a big boost to the whole electrical system.
You are correct of course, given the list of possible culprits, it is going to be a process of elimination.
Having already removed the fuel rail in the course of a valley gasket swap, and for the cost of servicing the injectors, this course of action seems to make sense. At least if the report comes back and details that 3 of them needed some additional surgery, this might be a good pointer(?).
The car doesn’t suffer from a (detectable) miss-fire, only an occasional low-rev/speed ‘shunting’ when cold (like most Chim’s).
The HT leads are new(ish) and despite the wave of opinion against the B7ECS plugs, 5 show a good colour (and this was after an extensive idling period, whilst I checked the fan operation with an I/R thermometer). Maybe, if I’d just switched the engine off after the quick blast all plugs might’ve shown a good colour?
However, I am toying with the idea of changing to BPR7ES – ‘R’ because I have also invested in some Lava Rock Socks to ditch the extenders (which might also be contributing to the slight fouling of the (3) plugs, - although there’s no obvious damage on any of them).
I’ve not done a compression test as yet (but I do have a tester).
With regards to cam wear – an RV8 Achilles heel alright– I understand that some lobes are more prone to wear than others. I’ll check this against the plugs I’ve pulled (I’ve kept their cylinder numbers marked).
I’ll investigate the valve gear further in the course of the VG swap.
Otherwise, The engine seems in good health, only uses about 100ml of oil per 1k miles (but most of this seems to be coming from the valley gasket/sump joint), and doesn’t use any coolant. It always starts first time (at least since I fitted the David Beer hot-start relay), and only gets a bit fluffy if you touch the throttle immediately after starting when it’s very cold, but this soon clears.
I like the idea of an additional engine earth. I’ve fitted these in the past to get over a myriad of issues not related to GRP bodies, but due to general loom degradation and is a big boost to the whole electrical system.
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