Yet another rv8 rich idle headache..
Discussion
Unlucky48 said:
... Do you mean you’d expect the ecu to be adding less fuel in the r/guage screenshot?
Less fuel, yes.Just a thought, do you have an EVAP carbon canister and purge valve fitted to your car?
If so, check that it's connections and tubing are air tight.
The thread link I posted yesterday contains some blurb on how 14CUX purges the fuelling system, which does have an affect on rich and lean, especially at idle. It's a bit technical but I think you would get the jist. To find it do a Google search for carbon canister EVAP 14CUX pistonheads.
Thank you!
The car doesn’t have a carbon canister, never has although I can’t recall if it has something up inside the rear inner wing or not for tank breathers. I looked into it years ago and couldn’t find any real info on which cars have it and which don’t or why?.
Just did a quick google and found a guy a few miles away selling a 1999 14cux ecu from a late disvovery1 so that should have the latest fuel maps?
Also phoned a company (turners garage) up near Hemel which is about 50 miles on the trailer for the car who seem to suggest they know what they are doing with the old rv8 stuff. Garage hourly rates almost equal my daily rate so I don’t know whether to bite the bullet yet and book it in or not.
Also phoned v8d ready to give in and order one of their cams (want it working desperation is setting in..) but rob suggested It’s unlikely to be mechanical and to go check everything yet again before spending money. Top bloke!
The car doesn’t have a carbon canister, never has although I can’t recall if it has something up inside the rear inner wing or not for tank breathers. I looked into it years ago and couldn’t find any real info on which cars have it and which don’t or why?.
Just did a quick google and found a guy a few miles away selling a 1999 14cux ecu from a late disvovery1 so that should have the latest fuel maps?
Also phoned a company (turners garage) up near Hemel which is about 50 miles on the trailer for the car who seem to suggest they know what they are doing with the old rv8 stuff. Garage hourly rates almost equal my daily rate so I don’t know whether to bite the bullet yet and book it in or not.
Also phoned v8d ready to give in and order one of their cams (want it working desperation is setting in..) but rob suggested It’s unlikely to be mechanical and to go check everything yet again before spending money. Top bloke!
Where are you based? Personally I'd try running a non catalyst tune, like map 2 and see if you can get the idle mixture correct with the screw on the side of the AFM. Adding lambda feedback and trim just confused matters if the engine is misfiring. I take it you do have lambda probes? Trim does horrible things if you don't! I'm happy to put a chip socket in one of your ECUs for a nominal sum and a chip if needed if you message me your phone number so I can fully understand what's going on. Some tunes out there won't allow you to run a non catalyst tune, whatever resistor you have.
Thank you!
That is very kind. I’ve been putting off trying to solder a new chip into my power seat ecu for years as I get a bit gung ho with the iron so I shouldn’t be trusted with an important ecu.. I will definitely take you up on that kind offer, pm to follow.
I had been running the car on a cat tune but recently switched it to non cat to see if it helped with diagnosing the misfire but it hasn’t. Regardless of what I do the miss remains. I did mean to meter the lambdas
While on non cat as you’d suggested before but all the while it’s missing it will just be erroneous?
The car has new ntk lambdas which went in with the new engine as one of the old ones died from coolant poisoning. Currently a full stainless sports system without cat. I have made a removable cat but don’t want to fit it until this problem is solved.
It’s a real tricky one.
When I hooked out the previous engine that had sat for two years waiting for a new block it ran without fine even thought the rockers/ valves were covered in very heavy rust but right from first fire of the new engine it’s had the same over riding problem of a miss from cold which lessens to an off beat light miss once warm, pots 3&4 running a lot colder than the other 6 and all 8 plugs, exhaust and piston crowns showing identical over rich carbon.
I haven’t re-tried adjusting the afm trim in non cat. I did try it some time ago and going much lower than 0.8v made the idle begin to stumble/ hunt.
When I get time I’m going to go over the ego loom with a fine tooth comb in case I’ve missed something but all the sensors seem to be reporting properly back to the ecu plug.
That is very kind. I’ve been putting off trying to solder a new chip into my power seat ecu for years as I get a bit gung ho with the iron so I shouldn’t be trusted with an important ecu.. I will definitely take you up on that kind offer, pm to follow.
I had been running the car on a cat tune but recently switched it to non cat to see if it helped with diagnosing the misfire but it hasn’t. Regardless of what I do the miss remains. I did mean to meter the lambdas
While on non cat as you’d suggested before but all the while it’s missing it will just be erroneous?
The car has new ntk lambdas which went in with the new engine as one of the old ones died from coolant poisoning. Currently a full stainless sports system without cat. I have made a removable cat but don’t want to fit it until this problem is solved.
It’s a real tricky one.
When I hooked out the previous engine that had sat for two years waiting for a new block it ran without fine even thought the rockers/ valves were covered in very heavy rust but right from first fire of the new engine it’s had the same over riding problem of a miss from cold which lessens to an off beat light miss once warm, pots 3&4 running a lot colder than the other 6 and all 8 plugs, exhaust and piston crowns showing identical over rich carbon.
I haven’t re-tried adjusting the afm trim in non cat. I did try it some time ago and going much lower than 0.8v made the idle begin to stumble/ hunt.
When I get time I’m going to go over the ego loom with a fine tooth comb in case I’ve missed something but all the sensors seem to be reporting properly back to the ecu plug.
Starting to sound like an induction leak to me. Have you had heads skimmed?
By the way I would do exactly as Blitz says. Not many know the Cux or has spent more time helping people on here than him.
The thing will always come across as running rich until it’s properly revving with load on it I’d expect.
A talented Tvr friend somehow knocked his inlet manifold gasket while reassembling his top end causing one of the tabs to bend over thus causing a horrendous air leak which stopped I think both 3and 5 from firing. It took some time to find it as it was not obvious.
By the way I would do exactly as Blitz says. Not many know the Cux or has spent more time helping people on here than him.
The thing will always come across as running rich until it’s properly revving with load on it I’d expect.
A talented Tvr friend somehow knocked his inlet manifold gasket while reassembling his top end causing one of the tabs to bend over thus causing a horrendous air leak which stopped I think both 3and 5 from firing. It took some time to find it as it was not obvious.
The bottom line here is all the injectors fire together for the same period per bank. So if two cylinders are mis firing it has to be something unique to those cylinders. Its nothing to do with the ECU or fuel trim. If you want to ensure the mixture is somewhere near correct on the working side, put a test meter on the lambda output and run a non catalysts map- the green one preferably as its a known quantity. Then go back to the AFM screw on a warm engine, and alter the CO trim and monitor the lambda output on THE GOOD BANK, and it should be perfectly possible to get it to switch suddenly from 0 volts (poor idle as its too lean) to 1.2 or over as the mixture richens. If you carry on it will start to sound like its running on choke and you might see a small increase in voltage on the output, but only fractions of a volt. The lambdas are set to switch at 14.7:1 AFR, but this is really a bit lean for the old RV8 at idle, so give it a turn or two more on the AFM screw once its switched, and you wont be far out. The expected voltage range is 1 to 1.5 volts on the CO trim.
You now have the mixture correct on one bank, so the second should not be a mile out. They do vary a bit due to the plenum air feed position, but not enough to make a big difference.
Now concentrate on the two failing cylinder- you only have limited options:
1) HT- Plugs not firing, leads mixed up or faulty , dizzy cap tracking, missing carbon brush
2) Local air leaks to those inlet ports
3) Loss of compression on those cylinders
4) faulty Injectors.
Forget everything about maps, fuel trim, lambda feedback and concentrate on the basics, as it was described to me, lambda trim is like trying to put up a level shelf on a boat in a storm, so you really need the boat in dry dock to start with to diagnose it, i.e, no trim.
Edited to add lambda wire output is black +ve output , white ground, voltage range 0-2v DC.
You now have the mixture correct on one bank, so the second should not be a mile out. They do vary a bit due to the plenum air feed position, but not enough to make a big difference.
Now concentrate on the two failing cylinder- you only have limited options:
1) HT- Plugs not firing, leads mixed up or faulty , dizzy cap tracking, missing carbon brush
2) Local air leaks to those inlet ports
3) Loss of compression on those cylinders
4) faulty Injectors.
Forget everything about maps, fuel trim, lambda feedback and concentrate on the basics, as it was described to me, lambda trim is like trying to put up a level shelf on a boat in a storm, so you really need the boat in dry dock to start with to diagnose it, i.e, no trim.
Edited to add lambda wire output is black +ve output , white ground, voltage range 0-2v DC.
Edited by blitzracing on Friday 23 April 18:09
Classic Chim said:
Starting to sound like an induction leak to me. Have you had heads skimmed?
By the way I would do exactly as Blitz says. Not many know the Cux or has spent more time helping people on here than him.
The thing will always come across as running rich until it’s properly revving with load on it I’d expect.
A talented Tvr friend somehow knocked his inlet manifold gasket while reassembling his top end causing one of the tabs to bend over thus causing a horrendous air leak which stopped I think both 3and 5 from firing. It took some time to find it as it was not obvious.
How dare you insinuate that I am "talented", I demand you retract that statement. ........By the way I would do exactly as Blitz says. Not many know the Cux or has spent more time helping people on here than him.
The thing will always come across as running rich until it’s properly revving with load on it I’d expect.
A talented Tvr friend somehow knocked his inlet manifold gasket while reassembling his top end causing one of the tabs to bend over thus causing a horrendous air leak which stopped I think both 3and 5 from firing. It took some time to find it as it was not obvious.
Thanks guys
I appreciate your continued help with this.
Problem is I have one cylinder on each bank misfiring/ running much colder.
Cyls 3&4 so second one in from front on each bank hence not being able to get a good base mixture clue.
I know it’s no guarantee of working parts but the car now has new oe fuel pump, new genuine regulator and I know I’ll be chastised for doing it while chasing a problem but new Bosch 4 hole injectors as per injector thread on here. One of my lucas ones was weeping and the Bosch ones seem much better value than spending money on old tech.
Fuel pressure is doing exactly what it’s supposed to.
Just fitted yet another brand new genuine dizzy cap and rotor yesterday with a choice of new lucas (crap) or magnecor leads, made no difference. Dizzy is a known good working one and has been pulled apart and checked, weights and pickup in perfect order. I have tried two other dizzies also with no change in symptoms.
I have done heaps of leak checking, even measured the ‘squish’ of the valley gasket and I can find no leak anywhere.
The heads have been skimmed and the block decked by a total of around 0.5mm and I was worried about inlet manifold fit but It actually seems to line up with the bolt holes and ports better than it ever did!
My mechanical ear told me right from the off that it sounds like an air leak or possibly valve problem but if it is then I’ve not found it and I’ve been looking for months now..
I’ve just ordered a smoke test machine so i’ll check again when it arrives.
I would have thought if it had an air leak in two cylinders, one on each bank that at least those two plugs would show a different colour to the rest but they all look identical. The miss is definitely rhythmic not random so I don’t think I need to look at the other cyls yet.
I appreciate your continued help with this.
Problem is I have one cylinder on each bank misfiring/ running much colder.
Cyls 3&4 so second one in from front on each bank hence not being able to get a good base mixture clue.
I know it’s no guarantee of working parts but the car now has new oe fuel pump, new genuine regulator and I know I’ll be chastised for doing it while chasing a problem but new Bosch 4 hole injectors as per injector thread on here. One of my lucas ones was weeping and the Bosch ones seem much better value than spending money on old tech.
Fuel pressure is doing exactly what it’s supposed to.
Just fitted yet another brand new genuine dizzy cap and rotor yesterday with a choice of new lucas (crap) or magnecor leads, made no difference. Dizzy is a known good working one and has been pulled apart and checked, weights and pickup in perfect order. I have tried two other dizzies also with no change in symptoms.
I have done heaps of leak checking, even measured the ‘squish’ of the valley gasket and I can find no leak anywhere.
The heads have been skimmed and the block decked by a total of around 0.5mm and I was worried about inlet manifold fit but It actually seems to line up with the bolt holes and ports better than it ever did!
My mechanical ear told me right from the off that it sounds like an air leak or possibly valve problem but if it is then I’ve not found it and I’ve been looking for months now..
I’ve just ordered a smoke test machine so i’ll check again when it arrives.
I would have thought if it had an air leak in two cylinders, one on each bank that at least those two plugs would show a different colour to the rest but they all look identical. The miss is definitely rhythmic not random so I don’t think I need to look at the other cyls yet.
Classichimi referred to me with bent gasket and that caused 2 cold cylinders 5 n 7. In my quest to find what was causing 5 n 7 to be cold I tried to work out if it was fuel or ignition as primary issue.
I bought some (8) spark detectors and fitted 1 to each plug, all 8 were firing fine so that eliminated ignition as the problem.
I will find the linky for them asap
Edit to add
https://www.machinemart.co.uk/p/laser-2780-high-te...
I bought some (8) spark detectors and fitted 1 to each plug, all 8 were firing fine so that eliminated ignition as the problem.
I will find the linky for them asap
Edit to add
https://www.machinemart.co.uk/p/laser-2780-high-te...
Thanks guys
I have some sparky test things, blitz suggested trying them some time ago. Typically I couldn’t see any difference in spark occurrence or brightness between good and bad cylinders.
After that I tried two colourtune plugs side by side in a good and adjacent bad cylinder to see if I could see what was going on or notice a difference and it was inconclusive. The engine didn’t seem to like them and although I could see they were sparking consistently they didn’t seem to ignite consistently in either cylinder. I only used them for 3-4 minutes and when I removed them they had already begun to get a very thin film of black carbon on them. That was with the old Lucas injectors in though so I should probably try them again.
After that I re-checked injector flow rates and all 8 flowed the same, top end of spec. That’s when I noticed that one was letting by slightly after power off so ordered new ones. I haven’t re-checked flow since fitting the new ones.
Do the spark tester things only light up if the plug has fired or do they light up if current is passing TO the plug? I assume the latter which won’t help me know if the charge is actually igniting each time?
The bent valley gasket must have been a pain! Can I ask what the symptoms were? How did the engine behave besides the misfire? Any noises or idle issues? Did it cause any similar symptoms to my mess?
Once warm and ignoring the mot failing emissions the car drives well above idle whether on light throttle or planted and is making very good mid- top end power. only exception being the idle seems to remain 150ish rpm too high when I come off the gas, pushes the car along for a while until it settles. (Auto box) same pulling up to junctions, when slowing the idle just pushes the car along a touch more than it should and takes 10 secs or so after stopping to settle where it should.
Being a dinosaur I wish I could just slap a carb and points dissy on it, disconnect it from the trickery and see if the engine runs fine without the extra bits..
I have some sparky test things, blitz suggested trying them some time ago. Typically I couldn’t see any difference in spark occurrence or brightness between good and bad cylinders.
After that I tried two colourtune plugs side by side in a good and adjacent bad cylinder to see if I could see what was going on or notice a difference and it was inconclusive. The engine didn’t seem to like them and although I could see they were sparking consistently they didn’t seem to ignite consistently in either cylinder. I only used them for 3-4 minutes and when I removed them they had already begun to get a very thin film of black carbon on them. That was with the old Lucas injectors in though so I should probably try them again.
After that I re-checked injector flow rates and all 8 flowed the same, top end of spec. That’s when I noticed that one was letting by slightly after power off so ordered new ones. I haven’t re-checked flow since fitting the new ones.
Do the spark tester things only light up if the plug has fired or do they light up if current is passing TO the plug? I assume the latter which won’t help me know if the charge is actually igniting each time?
The bent valley gasket must have been a pain! Can I ask what the symptoms were? How did the engine behave besides the misfire? Any noises or idle issues? Did it cause any similar symptoms to my mess?
Once warm and ignoring the mot failing emissions the car drives well above idle whether on light throttle or planted and is making very good mid- top end power. only exception being the idle seems to remain 150ish rpm too high when I come off the gas, pushes the car along for a while until it settles. (Auto box) same pulling up to junctions, when slowing the idle just pushes the car along a touch more than it should and takes 10 secs or so after stopping to settle where it should.
Being a dinosaur I wish I could just slap a carb and points dissy on it, disconnect it from the trickery and see if the engine runs fine without the extra bits..
You can get a stack load of information from failing cylinders by looking at the HT voltages. On a good plug, the voltage rises until the arc starts and then levels off during the burn period. The point the arc starts depends on the compression and mixture density so it's normal to see peak HT vary a bit under different engine loads. It also varies depending on the HT lead type length and total arc gap Inc the rotor to pick up point and plug gap. A break in HT lines gives a higher peak, a shorted HT line or sooty plug much lower. The old style Crypton tune had a facility to read peak HT on a scope so you could compare cylinders, but I think you will be lucky to find a working one these days but worth asking any local classic car specialists.
Gunson used to do a great led bar graph tester, but it's long been out of production, although I do have one if needed. As for the neon type plug caps, they will need a path to ground on the plug side when it arcs to get them to light, but you have color tunes that will work just as well if you are looking for a spark in the failing chamber. Just use them in a low light condition. I'm really surprised you can't see the difference in burn between good and bad cylinders if the header temps are so different.
Gunson used to do a great led bar graph tester, but it's long been out of production, although I do have one if needed. As for the neon type plug caps, they will need a path to ground on the plug side when it arcs to get them to light, but you have color tunes that will work just as well if you are looking for a spark in the failing chamber. Just use them in a low light condition. I'm really surprised you can't see the difference in burn between good and bad cylinders if the header temps are so different.
Mark,
I have no idea how you remember all this stuff but I am very grateful for the info!
I don’t have anything more technical than a dvm for measuring. It would be great to be able to measure/ scope somehow the sparks to see what each cylinder is actually doing.
I saw someone on tv using a colourtune the other day and they used an old kitchen roll tube around it to make it darker. I didn’t try using the supplied thin black tubes before but i’ll add that to the list of things to try and see if it helps see the combustion colour more clearly.
I have no idea how you remember all this stuff but I am very grateful for the info!
I don’t have anything more technical than a dvm for measuring. It would be great to be able to measure/ scope somehow the sparks to see what each cylinder is actually doing.
I saw someone on tv using a colourtune the other day and they used an old kitchen roll tube around it to make it darker. I didn’t try using the supplied thin black tubes before but i’ll add that to the list of things to try and see if it helps see the combustion colour more clearly.
Unlucky48 said:
Mark,
I have no idea how you remember all this stuff but I am very grateful for the info!
I don’t have anything more technical than a dvm for measuring. It would be great to be able to measure/ scope somehow the sparks to see what each cylinder is actually doing.
I saw someone on tv using a colourtune the other day and they used an old kitchen roll tube around it to make it darker. I didn’t try using the supplied thin black tubes before but i’ll add that to the list of things to try and see if it helps see the combustion colour more clearly.
Before you go that far, just try an ordinary strobe that clips onto the HT lead on each plug line in turn and see if you get the same regular firing pattern on each of the 8 leads. The strobes need a decent HT spike to trigger, so if the HT voltages are low the firing will be intermittent. Do you have access to one? I have no idea how you remember all this stuff but I am very grateful for the info!
I don’t have anything more technical than a dvm for measuring. It would be great to be able to measure/ scope somehow the sparks to see what each cylinder is actually doing.
I saw someone on tv using a colourtune the other day and they used an old kitchen roll tube around it to make it darker. I didn’t try using the supplied thin black tubes before but i’ll add that to the list of things to try and see if it helps see the combustion colour more clearly.
Also - as both banks are playing up- double check the rotor arm is in line with the number one lead take off at the point of firing- I dont think its possible to get it wrong unless the cam timing is out, but worth checking anyway and there are two ways to do this
1) Mark a line vertically from the number 1 plug lead in the dizzy cap and mark the distributor body with a bit of paint. Remove the dizzy cap and rotate the engine to number one firing- about 8' BTDC. Now check the rotor arm conductor is aligned very near paint mark on the distributor The brass conductor is quite wide, so basically you have about 15' of sweep across the tip between static timing and maximum advance, so the arc point moves across the rotor blade tip as the timing changes. If you rotor tip goes outside this sweep the the arc gap gets too wide and the spark will fail to jump the gap.
2) More reliable than paint- take an old dizzy cap and cut a big hole between the number one plug take off and king lead take off, then simply look down through the hole and check the rotor is in the correct position.
Dave- i’ll have to take a look tomorrow as I can’t recall what’s on the idle valve as I have three used ones and have been playing around with them. The one that’s in there at the moment seemed to give the lowest cold start idle (although still 1600 rpm) I think it has a genuine type thin paper gasket but will check. Before the engine swap it had either a copper washer or a thin rubber o-ring. Idle was less temperamental then and either seemed fine but I understand what you are suggesting with the valve potentially being spaced too far off it’s seat.
Blitz- good shout. I do have a couple of timing lights so i’ll Give checking all leads for firing regularity a try!
As a side note the genuine from Land Rover classic rotor arm that came yesterday is not of the same build quality as an older genuine one. It’s still the thicker brass part but just doesn’t look as good, is missing the little drilled hole near the sparking end and no longer has Lucas stamped on it.
I decided to buy the spare ecu from that local guy today. It’s a 1997 one but for a 3.9. He bought it to trace a 4 year misfire on a 3.9 classic and gave up and sold the car..
i do have a poor quality dissy cap that i’ll happily cut open to watch the rotor arm position, good idea.
That’s a few things to try tomorrow if I get time and the smoke machine arrived so I’m hoping to be able to give that a dam good go in the hopes of a whisp of smoke from somewhere I’ve missed..
thanks guys!
Blitz- good shout. I do have a couple of timing lights so i’ll Give checking all leads for firing regularity a try!
As a side note the genuine from Land Rover classic rotor arm that came yesterday is not of the same build quality as an older genuine one. It’s still the thicker brass part but just doesn’t look as good, is missing the little drilled hole near the sparking end and no longer has Lucas stamped on it.
I decided to buy the spare ecu from that local guy today. It’s a 1997 one but for a 3.9. He bought it to trace a 4 year misfire on a 3.9 classic and gave up and sold the car..
i do have a poor quality dissy cap that i’ll happily cut open to watch the rotor arm position, good idea.
That’s a few things to try tomorrow if I get time and the smoke machine arrived so I’m hoping to be able to give that a dam good go in the hopes of a whisp of smoke from somewhere I’ve missed..
thanks guys!
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