Yet another rv8 rich idle headache..
Discussion
You still need to take 2 steps backwards- RoverGauge readings are really only valid if all cylinders are burning correctly, so you need to be 100% the basics are correct. When where the injectors last cleaned ? If you get poor combustion on cylinder it will throw out the settings for the rest of that bank. This is where multiple color tunes works well as its dead easy to see the difference in the burn. Can you check the exhaust header temp for each pot?, Try melting a cable tie on each one and see if they all melt at the same rate. As for compression I think you can put a squirt of oil down the pots with the low compression, then crank. If the pressure comes up its the valves that are leaking.
You are quite right. I wasn’t pinning much hope on roverguage pinpointing the fault it’s just useful to see the parameters such as idle valve etc that can’t be seen from more old fashioned diagnostics.
The injectors have never been professionally cleaned and have done big mileage but as the car ran spot on prior to the engine rebuild I had hoped giving them a blast with carb cleaner and fitting new filter baskets to them might suffice. I did do a leak test on them last week and none of them dropped even a single drop of fuel. Also checked they were all receiving the same signal while running and swapped the two suspect cylinders injectors for used spare ones to no avail.
I did look up colour tunes but at £30+ each as much as I’d like to I don’t think I can afford four of the buggers. I’ll order one and see if I can get any results. I assume it would be best to run the car on a non cat map for that so the lambdas aren’t trying to alter the fuelling over whatever the base map dictates?
It seems looking at the fuel maps that all three maps have the same base fuelling in the idle area so without lambda control fuelling would be the same and not alter at cold idle regardless of which map it’s running?
The injectors have never been professionally cleaned and have done big mileage but as the car ran spot on prior to the engine rebuild I had hoped giving them a blast with carb cleaner and fitting new filter baskets to them might suffice. I did do a leak test on them last week and none of them dropped even a single drop of fuel. Also checked they were all receiving the same signal while running and swapped the two suspect cylinders injectors for used spare ones to no avail.
I did look up colour tunes but at £30+ each as much as I’d like to I don’t think I can afford four of the buggers. I’ll order one and see if I can get any results. I assume it would be best to run the car on a non cat map for that so the lambdas aren’t trying to alter the fuelling over whatever the base map dictates?
It seems looking at the fuel maps that all three maps have the same base fuelling in the idle area so without lambda control fuelling would be the same and not alter at cold idle regardless of which map it’s running?
It seems colour tunes like a lot of kit is out of stock nearly everywhere but I’ve managed t order two from separate suppliers..
The exhaust header temps are easy to test as I have an ir thermometer and the car has ‘double s’ stainless tubular manifolds. While testing I was able to test right at the start of each runner as it exited the exhaust flange.
The exhaust header temps are easy to test as I have an ir thermometer and the car has ‘double s’ stainless tubular manifolds. While testing I was able to test right at the start of each runner as it exited the exhaust flange.
You are best running a non cat map for basic mixture tests. The base map settings for idle are just a starting point, you can add or remove 20% fuel with the long and short term trim. This makes life difficult as long term trim only moves if the engine is hot and left to idle for at least 2 1/2 minutes without any throttle input. Its an easy mistake to swap chips, or drop power off the ECU and look at the short term lambda or CO values straight afterwards before the long term has stabilised, and the base mixture is still incorrect. At least with the non cat map, the AFM voltage trim is fixed, so you have a consistent mixture locked against the voltage without waiting for the ECU to re learn the long term trim.
Thanks for that.
I’m not ready for any more running tests just yet. The inlet manifold is still off. I have been working on it today on my drive, freezing!.
Seems I made a faux pas during the build as the inlet manifold had made contact with one side of both front and rear valley gasket steel retaining thingies meaning it’s just possible that the front of the even bank and rear of odd bank were not fully seated against the valley gasket although it looks like it’s compressed well. there are sticky out reference bits on the underside of the manifold and they were heavily marked/scratched from the contact, now shaved down. I am sure they were fine first time I built up the engine but I guess the block being decked during the liner job made things a little tighter...
To check manifold fit I left the old valley gasket in place and put some strips of plastiguage vertically beside the front, mid and rear inlet ports and torqued the manifold down which left a nice even squish of plastiguage upon removal so I’m fairly confident that it should bolt up nice and square when I get to it.
I also did an injector flow test, fuel pressure was fine and they all flowed 105ml in 30 secs which is a little over what Haynes say at 195 per minute max but they all flowed exactly the same amount and the crappy single stream was just that with no wizzing off centre so I assume the Lucas injectors are ok for now.
I’m waiting on some adjustable pushrods arriving early next week. I built the engine with its old pushrods as I couldn’t really afford the adjustables but the lifter preloads are all over the place and while just inside spec at between 20-60 thou I’m not happy with it so going to make sure they are all spot on without need for rocker shims although that may mean the piston to valve clearance will become tighter..
I’m beginning to wish I’d just slapped together a stock engine and got on with something else!
I’m not ready for any more running tests just yet. The inlet manifold is still off. I have been working on it today on my drive, freezing!.
Seems I made a faux pas during the build as the inlet manifold had made contact with one side of both front and rear valley gasket steel retaining thingies meaning it’s just possible that the front of the even bank and rear of odd bank were not fully seated against the valley gasket although it looks like it’s compressed well. there are sticky out reference bits on the underside of the manifold and they were heavily marked/scratched from the contact, now shaved down. I am sure they were fine first time I built up the engine but I guess the block being decked during the liner job made things a little tighter...
To check manifold fit I left the old valley gasket in place and put some strips of plastiguage vertically beside the front, mid and rear inlet ports and torqued the manifold down which left a nice even squish of plastiguage upon removal so I’m fairly confident that it should bolt up nice and square when I get to it.
I also did an injector flow test, fuel pressure was fine and they all flowed 105ml in 30 secs which is a little over what Haynes say at 195 per minute max but they all flowed exactly the same amount and the crappy single stream was just that with no wizzing off centre so I assume the Lucas injectors are ok for now.
I’m waiting on some adjustable pushrods arriving early next week. I built the engine with its old pushrods as I couldn’t really afford the adjustables but the lifter preloads are all over the place and while just inside spec at between 20-60 thou I’m not happy with it so going to make sure they are all spot on without need for rocker shims although that may mean the piston to valve clearance will become tighter..
I’m beginning to wish I’d just slapped together a stock engine and got on with something else!
The colour tunes arrived yesterday so I thought I’d spend today in the snow fiddling with the car some more!
Top end all put back together and no difference whatsoever sadly.
I ran the engine literally for one minute and checked the plugs on the even side only as it was getting dark by then. Cyl 4, the sooty colder pot was totally black! The other evens were as before with partial black/ partial white on insulators.
Having a look down the plug holes it seems the piston tops are already coated in black carbon after only 300 miles, is that normal?
I put the colour tunes into pots 4&6 so I could hopefully see a difference in the colours between the two different temperature cylinders but it was hard to spot much of a difference. Guessing I’d say the sooty pot was more slight blue going towards yellow and the other was a light blue but after a minute or two it began to not ignite? I could clearly see the sparks still sparking but combustion seemed to come and go and maybe miss 6 or 8 shots before firing again while the sooty pot fired every time. Still confused..
I had a vacuum gauge and fuel pressure gauge hooked up while doing the tests at idle, fuel pressure stayed where it should at 35psi but plenum vacuum dropped from 14 running with proper plugs to 10 while using the colour tunes so I assume the engine doesn’t run as well with them?
I’m hoping something miraculous will occur and I can write an ‘it’s all fixed’ post but I don’t think that’s going to happen!
Top end all put back together and no difference whatsoever sadly.
I ran the engine literally for one minute and checked the plugs on the even side only as it was getting dark by then. Cyl 4, the sooty colder pot was totally black! The other evens were as before with partial black/ partial white on insulators.
Having a look down the plug holes it seems the piston tops are already coated in black carbon after only 300 miles, is that normal?
I put the colour tunes into pots 4&6 so I could hopefully see a difference in the colours between the two different temperature cylinders but it was hard to spot much of a difference. Guessing I’d say the sooty pot was more slight blue going towards yellow and the other was a light blue but after a minute or two it began to not ignite? I could clearly see the sparks still sparking but combustion seemed to come and go and maybe miss 6 or 8 shots before firing again while the sooty pot fired every time. Still confused..
I had a vacuum gauge and fuel pressure gauge hooked up while doing the tests at idle, fuel pressure stayed where it should at 35psi but plenum vacuum dropped from 14 running with proper plugs to 10 while using the colour tunes so I assume the engine doesn’t run as well with them?
I’m hoping something miraculous will occur and I can write an ‘it’s all fixed’ post but I don’t think that’s going to happen!
The fuel pressure is far too high- it should drop by about 8 psi at idle. There is a vacuum take off from the plenum that goes to the fuel pressure regulator, and this lowers the fuel pressure when there is a vacuum in the inlet. This ensures you get 37 psi between the injector fuel rail, and injector tip that is below atmospheric pressure, meaning the fuelling is consistent. Without this system you would suck fuel out of the injector depending on inlet vacuum, so go and check your vacuum pipe to the regulator.
Tricks for the color tune- Flicks of orange basically mean its running too rich- Have a play with the screw on the AFM on the green map- you should be able to make the burn go from orange (far too rich) to very pale blue as the engine leans out. Correct mixture is normally just at the point the orange content disappears, but before the point the idle becomes unstable as it leans out.
Tricks for the color tune- Flicks of orange basically mean its running too rich- Have a play with the screw on the AFM on the green map- you should be able to make the burn go from orange (far too rich) to very pale blue as the engine leans out. Correct mixture is normally just at the point the orange content disappears, but before the point the idle becomes unstable as it leans out.
Edited by blitzracing on Monday 25th January 17:31
Thanks again Mark!
Your knowledge is much appreciated.
I re checked the fuel pressure tonight and it offered a different value which is annoying..
Pump primed, engine off the gauge sat at 26psi and stayed at 26/27 while idling cold. I’ve no idea why it didn’t get up to its 35 ish primed that I’m
absolutely sure it did on sunday and I forgot to pull off the vac hose while running to see if it altered the pressure.
The fuel pump is bugging me anyhow as it’s a few year old britpart one bought in haste when the pump died and while I doubt it’s at fault I have a good s/h genuine Land Rover one on the shelf that I’ll fit just for good measure.
I might change the roof and doors as well In case that helps!.
Your knowledge is much appreciated.
I re checked the fuel pressure tonight and it offered a different value which is annoying..
Pump primed, engine off the gauge sat at 26psi and stayed at 26/27 while idling cold. I’ve no idea why it didn’t get up to its 35 ish primed that I’m
absolutely sure it did on sunday and I forgot to pull off the vac hose while running to see if it altered the pressure.
The fuel pump is bugging me anyhow as it’s a few year old britpart one bought in haste when the pump died and while I doubt it’s at fault I have a good s/h genuine Land Rover one on the shelf that I’ll fit just for good measure.
I might change the roof and doors as well In case that helps!.
Well if the fuel pressure is correct, can you get the mixture to run from rich to lean with the color tune with the AFM screw on the green map, and is it reasonably consistent across all cylinders? The two banks are a little different at best on green as you feed air from one side of the plenum, not down the middle, but they should be the same per bank.
Edited by blitzracing on Wednesday 27th January 16:33
Thanks Mark,
When I tried the colour tune last week in pots 4&6, 6 being one of 6 cyls that are producing 350c+ at idle and cyl 4 being same as cyl 3 and producing 150c at idle the combustion colours were different but I couldn’t make much sense of it.
I’m surprised with the amount of people who suggest using a thermometer to check exhaust temps if there’s a misfire issue that nobody has any reference temps to gauge mine against.
I tested the fuel pressure earlier when I got home from work. left overnight the gauge was sat at 20psi, primed it went to 26, cold idle it stayed the same and disconnecting the vac pipe from the stepper motor stub only made it go up to 27psi. I thought it should go to 35psi with the vac pipe pulled? Wondering if the spare fuel rail I’ve fitted has a sticky pressure relief valve? Not confident that’s the villain in the misfire anyhow.
The whole one cylinder in each bank running differently is driving me potty.. similar symptoms were displayed when the engine was first rebuilt before it shat itself and needed the top hats as at that time it had six pots with white insulators on plugs and cyls 3&4 were a reasonable brown but all had black carbon on plug bases after only a very short period. i admit this issue is testing my mechanical sanity but it seems to me with all the testing and swapping of ignition and injection parts that’s happened since then that it must be a fundamental issue (bottom
end, heads or cam) or unaltered component causing the problem of which there are very few..
the mantra of test and be sure of results before replacing anything is a good one as I’ve tested, found virtually nothing out of spec, replaced most things anyhow and the problem persists.
so I’m going to remind myself of all the simple combustion principles, find my leakdown tester to make double sure of anything there and verify against the compression figures, fit spare fuel pump/ filter and think before I tear into the guts of the engine again.
When I tried the colour tune last week in pots 4&6, 6 being one of 6 cyls that are producing 350c+ at idle and cyl 4 being same as cyl 3 and producing 150c at idle the combustion colours were different but I couldn’t make much sense of it.
I’m surprised with the amount of people who suggest using a thermometer to check exhaust temps if there’s a misfire issue that nobody has any reference temps to gauge mine against.
I tested the fuel pressure earlier when I got home from work. left overnight the gauge was sat at 20psi, primed it went to 26, cold idle it stayed the same and disconnecting the vac pipe from the stepper motor stub only made it go up to 27psi. I thought it should go to 35psi with the vac pipe pulled? Wondering if the spare fuel rail I’ve fitted has a sticky pressure relief valve? Not confident that’s the villain in the misfire anyhow.
The whole one cylinder in each bank running differently is driving me potty.. similar symptoms were displayed when the engine was first rebuilt before it shat itself and needed the top hats as at that time it had six pots with white insulators on plugs and cyls 3&4 were a reasonable brown but all had black carbon on plug bases after only a very short period. i admit this issue is testing my mechanical sanity but it seems to me with all the testing and swapping of ignition and injection parts that’s happened since then that it must be a fundamental issue (bottom
end, heads or cam) or unaltered component causing the problem of which there are very few..
the mantra of test and be sure of results before replacing anything is a good one as I’ve tested, found virtually nothing out of spec, replaced most things anyhow and the problem persists.
so I’m going to remind myself of all the simple combustion principles, find my leakdown tester to make double sure of anything there and verify against the compression figures, fit spare fuel pump/ filter and think before I tear into the guts of the engine again.
Edited by Unlucky48 on Wednesday 27th January 19:15
Edited by Unlucky48 on Wednesday 27th January 19:18
As you have such marked differences in exhaust temp- Double check your distributor rotor arm setting to make sure the rotor tip is just passing the relevant pick up point at the point the ignition would take place- ie at about 8' BTDC. I dont think its possible to easily get things too far out and get it to run, but the point is the arc of the rotor tip blade has to cover the width of the arc of the mechanical distributor advance (half crankshaft advance) plus the distance the spark can jump so you may have say 20' of available arc "jump" space. Just thinking you could be just outside this on the misfiring cylinders?? Pop a strobe on the leads one by one and see if you get a different firing pattern. I would not want to quote exhaust temps as solid cast manifolds would be different to a tubular header with less heat transfer.
Thanks again!
I was wondering about irregular or out of sync spark as it’s about the only thing I haven’t really checked properly other than the strobe sits dead right when setting timing and I could see sparks through the colour tune plugs.
I had pondered trying to mark up the crank pulley accurately with tippex so I could check some of the other cylinders with the strobe.
Someone else told me that the 4.2/4.3 should be timed to 9 degrees but there is very little factory info on these rarer motors. Cam company also recommends 3 degrees additional advance but I’ve currently left it at 6 deg. Will try fiddling with it again but it didn’t make any discernible difference to the misfire when I fiddled before.
Also while I’m sure it’s working fine I’ve dug out a spare low mileage 3.9 dizzy which I’m going to strip and fettle just to try at the weekend along with a change of fuel pump/ filter then move on to fuel pressure reg if pressure still doesn’t test out followed by total ignition system examination and run through all fuel/ ecu tests yet again.
Agreed in the difference in manifold temps. I was hoping there might be someone else who had run a thermometer over their tubular headers. It’s surprising how quickly they change temperature as when i ran it with the colour tunes in and it began to not fire in one of the hotter pots it went from 350deg c down to 60 in about 5 secs! I’m sure the headers never used to get as hot with the old expired 3.9 as they are at idle now although that did always run about as rich as a cat car was allowed to. When I first put the car back together a year ago now with the first rebuild while bedding the cam in the headers got so hot that they set light to the insulation on the starter main live wire..
I was wondering about irregular or out of sync spark as it’s about the only thing I haven’t really checked properly other than the strobe sits dead right when setting timing and I could see sparks through the colour tune plugs.
I had pondered trying to mark up the crank pulley accurately with tippex so I could check some of the other cylinders with the strobe.
Someone else told me that the 4.2/4.3 should be timed to 9 degrees but there is very little factory info on these rarer motors. Cam company also recommends 3 degrees additional advance but I’ve currently left it at 6 deg. Will try fiddling with it again but it didn’t make any discernible difference to the misfire when I fiddled before.
Also while I’m sure it’s working fine I’ve dug out a spare low mileage 3.9 dizzy which I’m going to strip and fettle just to try at the weekend along with a change of fuel pump/ filter then move on to fuel pressure reg if pressure still doesn’t test out followed by total ignition system examination and run through all fuel/ ecu tests yet again.
Agreed in the difference in manifold temps. I was hoping there might be someone else who had run a thermometer over their tubular headers. It’s surprising how quickly they change temperature as when i ran it with the colour tunes in and it began to not fire in one of the hotter pots it went from 350deg c down to 60 in about 5 secs! I’m sure the headers never used to get as hot with the old expired 3.9 as they are at idle now although that did always run about as rich as a cat car was allowed to. When I first put the car back together a year ago now with the first rebuild while bedding the cam in the headers got so hot that they set light to the insulation on the starter main live wire..
The advance is a bit of a topic. You can add a load of advance at idle by removing the ported vacuum take off to the dizzy just above the throttle plate, then blocking it off. Then drill a new hole anywhere in the plenum body and fit a pipe you can put the dizzy pipe onto. This allows more vacuum advance on at idle, and the engines run a lot better this way. You don't need to make any other timing changes to do this, but it does need swapping back at mot time because it puts up the emissions.
If you simply move the dizzy to advance the timing, you move the whole timing curve and the absolute maximum mechanical advance is about 36' for the RV8 engine, (pushing your luck time) but engine size does come into it due to the speed of the flame front across the larger area. I think the stock timing peaks at about 28' so you have a reasonable safety margin if you wind the dizzy setting a few degrees. I've spent many fruitless hours trying to detect knock on the RV8, and never managed it so don't try the old trick of listening for knock and then backing it off.
If you simply move the dizzy to advance the timing, you move the whole timing curve and the absolute maximum mechanical advance is about 36' for the RV8 engine, (pushing your luck time) but engine size does come into it due to the speed of the flame front across the larger area. I think the stock timing peaks at about 28' so you have a reasonable safety margin if you wind the dizzy setting a few degrees. I've spent many fruitless hours trying to detect knock on the RV8, and never managed it so don't try the old trick of listening for knock and then backing it off.
Thanks for that Mark.
I’ve prepped the spare 3.9 dissy which seems all good and ready for fitting tomorrow, although its forecast rain all day. Will see how far through the test/ repair list I can get. I used the little vac pipe that came off the fuel pressure regulator to do suck tests on vac advance modules today (replaced with a new hose on car) and got a mouthful of yucky petrol taste so it looks like the suspect fpr is leaking as well as not giving correct pressure.
I haven’t ever pushed my luck with static timing on the old bus. Only time I have ever heard pinging was last week doing hot starts and testing stuff, a couple of times it did a nice old rattle as it fired.
I did run the old engine at 12 deg as it seemed to help when running on lpg but that’s all disconnected until I’m happy that the engine is good which is a pain in some ways as it’s a great way to rule out petrol system issues during bad running.
If I ever get it running right I may try the moving to manifold vacuum as I’m interested to see how it alters how the car behaves.
I’ve prepped the spare 3.9 dissy which seems all good and ready for fitting tomorrow, although its forecast rain all day. Will see how far through the test/ repair list I can get. I used the little vac pipe that came off the fuel pressure regulator to do suck tests on vac advance modules today (replaced with a new hose on car) and got a mouthful of yucky petrol taste so it looks like the suspect fpr is leaking as well as not giving correct pressure.
I haven’t ever pushed my luck with static timing on the old bus. Only time I have ever heard pinging was last week doing hot starts and testing stuff, a couple of times it did a nice old rattle as it fired.
I did run the old engine at 12 deg as it seemed to help when running on lpg but that’s all disconnected until I’m happy that the engine is good which is a pain in some ways as it’s a great way to rule out petrol system issues during bad running.
If I ever get it running right I may try the moving to manifold vacuum as I’m interested to see how it alters how the car behaves.
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