Help with over-fuelling TDV8
Discussion
Working on the assumption that the engine is indeed pulling in more air on one side that the other, the only things I could be drawing the air in is the engine itself or possibly some kind of positive crankcase ventilation system, but a quick look confirms it is a common system to both banks, so that rules that out.
Which means it has to be the engine, my question about fault codes was me wondering if the valve timing had slipped on one cylinder leading to it effectively pumping the air and fuel straight out the engine, because the timing being out would register a code, so that rules that out.
The fact it started to do it over night and was running fine the day before, sort of rules out a compression issue and the air being ejected via the breather.
A thought just occurred to me, does it have inlet throttles?
Which means it has to be the engine, my question about fault codes was me wondering if the valve timing had slipped on one cylinder leading to it effectively pumping the air and fuel straight out the engine, because the timing being out would register a code, so that rules that out.
The fact it started to do it over night and was running fine the day before, sort of rules out a compression issue and the air being ejected via the breather.
A thought just occurred to me, does it have inlet throttles?
I am no diesel mech, no where near clever enough! - But.. In the old days diesels used to drink as much air as they could, and then they worked as hard as the amount of diesel that is squirted in.
With that in mind, if the air was being pushed into the engine, and the extra fuel was being pushed into the engine, why is the fuel not burning and taking the engine to max revs?
This is once again making me think that if you stick an airline into a large cork and jammed it into the pipe before the MAF, it "should" leak somewhere after the MAF and before the engine. - Maybe?
Are there any cross-over pipes between the banks? - would a dump valve be sticking open, allowing the turbo to suck air in and just push it straight out the dump valve?
With that in mind, if the air was being pushed into the engine, and the extra fuel was being pushed into the engine, why is the fuel not burning and taking the engine to max revs?
This is once again making me think that if you stick an airline into a large cork and jammed it into the pipe before the MAF, it "should" leak somewhere after the MAF and before the engine. - Maybe?
Are there any cross-over pipes between the banks? - would a dump valve be sticking open, allowing the turbo to suck air in and just push it straight out the dump valve?
Peanut Gallery said:
I am no diesel mech, no where near clever enough! - But.. In the old days diesels used to drink as much air as they could, and then they worked as hard as the amount of diesel that is squirted in.
With that in mind, if the air was being pushed into the engine, and the extra fuel was being pushed into the engine, why is the fuel not burning and taking the engine to max revs?
This is once again making me think that if you stick an airline into a large cork and jammed it into the pipe before the MAF, it "should" leak somewhere after the MAF and before the engine. - Maybe?
Are there any cross-over pipes between the banks? - would a dump valve be sticking open, allowing the turbo to suck air in and just push it straight out the dump valve?
Modern diesels do have throttle bodies now, so in theory fuel metering is more accurate, the aim is to achieve stoichiometric combustion to reduce NOx emissions. Throttle closed, there isn’t enough oxygen to burn all the diesel injected, hence the white smoke.With that in mind, if the air was being pushed into the engine, and the extra fuel was being pushed into the engine, why is the fuel not burning and taking the engine to max revs?
This is once again making me think that if you stick an airline into a large cork and jammed it into the pipe before the MAF, it "should" leak somewhere after the MAF and before the engine. - Maybe?
Are there any cross-over pipes between the banks? - would a dump valve be sticking open, allowing the turbo to suck air in and just push it straight out the dump valve?
Thanks all for continued suggestions, really appreciate it!
Megaflow said:
A thought just occurred to me, does it have inlet throttles?
It does, and both sides are working (and swapped between them). The data when running both sides were showing the same values.Peanut Gallery said:
I am no diesel mech, no where near clever enough! - But.. In the old days diesels used to drink as much air as they could, and then they worked as hard as the amount of diesel that is squirted in.
With that in mind, if the air was being pushed into the engine, and the extra fuel was being pushed into the engine, why is the fuel not burning and taking the engine to max revs?
That was my thought as well, but it's running so rich it's not combusting properly, hence not producing enough power to raise the revs.With that in mind, if the air was being pushed into the engine, and the extra fuel was being pushed into the engine, why is the fuel not burning and taking the engine to max revs?
Peanut Gallery said:
Are there any cross-over pipes between the banks? - would a dump valve be sticking open, allowing the turbo to suck air in and just push it straight out the dump valve?
Nope, they're effectively completely independent in terms of gas flow and sensors etc - two of everything.Have you considered that the EGRs may not be working properly?
On my old 3.6TDV8 it was running s
te and I put it into my local specialist. They checked it all out, no error codes so suspected turbos were on way out. Swapped both, made no difference although old ones were starting to go.
Much head scratching, no obvious reason what the problem could be. Eventually they started a strip down to try and find something wrong and had their eureka moment when they took of the EGR valves... one of them was missing the end of the valve stem. The car thought the valve was operating as expected, the garage had been able to hear it operating as normal, but it just wasn't sealing (or opening) as it should have done, effecively it was just wide open all the time.
My paperwork for the car showed that the EGRs had been replaced by the previous owner several tens of thousands of miles previously, but he hadn't used JLR EGRs, he'd got some cheapies from China, and the valve head had just snapped off.
Made the car run like a bh, chugging and smoking all over the place.
On my old 3.6TDV8 it was running s
te and I put it into my local specialist. They checked it all out, no error codes so suspected turbos were on way out. Swapped both, made no difference although old ones were starting to go.Much head scratching, no obvious reason what the problem could be. Eventually they started a strip down to try and find something wrong and had their eureka moment when they took of the EGR valves... one of them was missing the end of the valve stem. The car thought the valve was operating as expected, the garage had been able to hear it operating as normal, but it just wasn't sealing (or opening) as it should have done, effecively it was just wide open all the time.
My paperwork for the car showed that the EGRs had been replaced by the previous owner several tens of thousands of miles previously, but he hadn't used JLR EGRs, he'd got some cheapies from China, and the valve head had just snapped off.
Made the car run like a b
h, chugging and smoking all over the place.Piersman2 said:
Have you considered that the EGRs may not be working properly?
On my old 3.6TDV8 it was running ste and I put it into my local specialist. They checked it all out, no error codes so suspected turbos were on way out. Swapped both, made no difference although old ones were starting to go.
Much head scratching, no obvious reason what the problem could be. Eventually they started a strip down to try and find something wrong and had their eureka moment when they took of the EGR valves... one of them was missing the end of the valve stem. The car thought the valve was operating as expected, the garage had been able to hear it operating as normal, but it just wasn't sealing (or opening) as it should have done, effecively it was just wide open all the time.
My paperwork for the car showed that the EGRs had been replaced by the previous owner several tens of thousands of miles previously, but he hadn't used JLR EGRs, he'd got some cheapies from China, and the valve head had just snapped off.
Made the car run like a bh, chugging and smoking all over the place.
At first I thought that was a non starter of an idea. But it has some merit, an open EGR would not be able to meter the flow and just pull as much as in as it could get, and because the air has already been thought the combustion chamber, the oxygen has been depleted and can't burn anymore fuel, hence the unburnt diesel.On my old 3.6TDV8 it was running s
te and I put it into my local specialist. They checked it all out, no error codes so suspected turbos were on way out. Swapped both, made no difference although old ones were starting to go.Much head scratching, no obvious reason what the problem could be. Eventually they started a strip down to try and find something wrong and had their eureka moment when they took of the EGR valves... one of them was missing the end of the valve stem. The car thought the valve was operating as expected, the garage had been able to hear it operating as normal, but it just wasn't sealing (or opening) as it should have done, effecively it was just wide open all the time.
My paperwork for the car showed that the EGRs had been replaced by the previous owner several tens of thousands of miles previously, but he hadn't used JLR EGRs, he'd got some cheapies from China, and the valve head had just snapped off.
Made the car run like a b
h, chugging and smoking all over the place.Krikkit said:
Thanks guys, I'm pretty sure that's not the issue as I can set the EGR to 0%, and you can hear it closing, but for the sake of an hour or so removing the inlet and loom I'll triple-check it
How could you check what the EGR is doing while the engine is running? - (I'm not asking for me, I'm asking as a train of thought, but wouldn't mind knowing anyway) - or set it to closed and then unplug it so it stays closed then start the car?As in could the EGR be working, but the car is getting a setting confused and is pumping air straight out of the exhaust, but thinks the air is going into the engine? - How hard would it be to swop either the actual EGR from one bank to the other, or to swop the wiring (or piping) across the banks?
(Maybe something like the old school fuel tank gauges, when the float gets to the bottom, it drops off the end of the resistor and then the gauge shows full, leading to a walk of shame to the petrol station...)
The EGR has a separate position sensing circuit, so the ECU can read its requested and actual positions, if they don't match it can adjust the opening within certain bounds, when it's outside the adjust limit it'll throw a code.
Currently they're <1% different between requested and sensed position, but there is a chance that's the issue and both are incorrect. That wouldn't really explain the high airflow at the inlet, but definitely worth checking.
Currently they're <1% different between requested and sensed position, but there is a chance that's the issue and both are incorrect. That wouldn't really explain the high airflow at the inlet, but definitely worth checking.
I have done some googling on this, and I think it is worth removing the EGR valves for a closer inspection.
This thread has very similar issues and the fault was the head of the EGR valve breaking off, there was no associated fault codes because the valve was still moving so the ECM didn't know there was anything wrong.
Also might be worth checking the combi IMAP/IMAT sensor as it seems they get gunked up which won't help.
https://www.fullfatrr.com/forum/topic33905-15.html
This thread has very similar issues and the fault was the head of the EGR valve breaking off, there was no associated fault codes because the valve was still moving so the ECM didn't know there was anything wrong.
Also might be worth checking the combi IMAP/IMAT sensor as it seems they get gunked up which won't help.
https://www.fullfatrr.com/forum/topic33905-15.html
Megaflow said:
I have done some googling on this, and I think it is worth removing the EGR valves for a closer inspection.
This thread has very similar issues and the fault was the head of the EGR valve breaking off, there was no associated fault codes because the valve was still moving so the ECM didn't know there was anything wrong.
https://www.fullfatrr.com/forum/topic33905-15.html
Thanks, as I said I don't think this will be the issue as the amount of fuel/smoke is much more pronounced than your usual bad EGR, and they were new not long ago, BUT I'll fetch it out this weekend to test.This thread has very similar issues and the fault was the head of the EGR valve breaking off, there was no associated fault codes because the valve was still moving so the ECM didn't know there was anything wrong.
https://www.fullfatrr.com/forum/topic33905-15.html
Megaflow said:
Also might be worth checking the combi IMAP/IMAT sensor as it seems they get gunked up which won't help.
Checked/swapped both MAP and MAF/IAT (which are combined). The MAP I keep removing and cleaning every few minutes of running as it's getting coated in fuel/oil stuff.Krikkit said:
Thanks guys, I'm pretty sure that's not the issue as I can set the EGR to 0%, and you can hear it closing, but for the sake of an hour or so removing the inlet and loom I'll triple-check it
Yep, as I said, my garage , very experienced local Land Rover specialists, could hear it opening and closing, the ECU thought it was opening and closing, but the actual physically missing valve head meant it was actually never closing.Took them several weeks to suss it, and only when nothing was making sense did they start to strip bits off. They'd never seen another behaving like this and were perplexed to say the least.
They were cock-a-hoop when they found the EGR head was missing as it all suddenly made sense to them. It was just an issue they had never seen before because of the cheap chinesium EGRs that has been fitted previously. They only fit JLR parts for just this type of reason.
Can you swap the MAF's from one side to another?
It's not possible for an idling diesel to use 10x the air. The throttle bodies on a diesel are only for emissions control (drive EGR flow, soft shut-down etc).
White smoke is incomplete combustion where diesel is injected too late to burn. Overfuelling at the correct timing gives you black smoke.
Does it have a DPF on each side? Injecting diesel late is used to help DPF heating/burning.
It's not possible for an idling diesel to use 10x the air. The throttle bodies on a diesel are only for emissions control (drive EGR flow, soft shut-down etc).
White smoke is incomplete combustion where diesel is injected too late to burn. Overfuelling at the correct timing gives you black smoke.
Does it have a DPF on each side? Injecting diesel late is used to help DPF heating/burning.
What dpf regen does your car have?
As in, when it is doing a regen, does the car push a bunch of air and fuel into the dpf, which should burn it out, but something has cooked?
(up until 2015 the old mondeo used to have a separate fuel injector that pumped fuel straight into the dpf, since then they use the normal injectors but pump the fuel in during the exhaust stroke I think (very very layman's terms))
I am asking cause if all the air that was going past the maf was being mixed with the over amount of fuel, I thought the engine would rev high, but if the fuel is being injected into a cold exhaust it would not burn and would blow white smoke??
As in, when it is doing a regen, does the car push a bunch of air and fuel into the dpf, which should burn it out, but something has cooked?
(up until 2015 the old mondeo used to have a separate fuel injector that pumped fuel straight into the dpf, since then they use the normal injectors but pump the fuel in during the exhaust stroke I think (very very layman's terms))
I am asking cause if all the air that was going past the maf was being mixed with the over amount of fuel, I thought the engine would rev high, but if the fuel is being injected into a cold exhaust it would not burn and would blow white smoke??
Kiwibacon said:
Can you swap the MAF's from one side to another?
It's not possible for an idling diesel to use 10x the air. The throttle bodies on a diesel are only for emissions control (drive EGR flow, soft shut-down etc).
White smoke is incomplete combustion where diesel is injected too late to burn. Overfuelling at the correct timing gives you black smoke.
Does it have a DPF on each side? Injecting diesel late is used to help DPF heating/burning.
He has already done that. The problem stays on the same bank so it is not the MAF.It's not possible for an idling diesel to use 10x the air. The throttle bodies on a diesel are only for emissions control (drive EGR flow, soft shut-down etc).
White smoke is incomplete combustion where diesel is injected too late to burn. Overfuelling at the correct timing gives you black smoke.
Does it have a DPF on each side? Injecting diesel late is used to help DPF heating/burning.
nelly1 said:
Could it be a timing issue?
If the chain tensioner for that bank has failed mechanically then the timing could be out just on that side.
I wondered about that, but I'm pretty sure the ECU would pick up a timing issue and flag a code.If the chain tensioner for that bank has failed mechanically then the timing could be out just on that side.
Piersman2 said:
Have you considered that the EGRs may not be working properly?
On my old 3.6TDV8 it was running ste and I put it into my local specialist. They checked it all out, no error codes so suspected turbos were on way out. Swapped both, made no difference although old ones were starting to go.
Much head scratching, no obvious reason what the problem could be. Eventually they started a strip down to try and find something wrong and had their eureka moment when they took of the EGR valves... one of them was missing the end of the valve stem. The car thought the valve was operating as expected, the garage had been able to hear it operating as normal, but it just wasn't sealing (or opening) as it should have done, effecively it was just wide open all the time.
My paperwork for the car showed that the EGRs had been replaced by the previous owner several tens of thousands of miles previously, but he hadn't used JLR EGRs, he'd got some cheapies from China, and the valve head had just snapped off.
Made the car run like a bh, chugging and smoking all over the place.
Well I owe you a pint (or several) for this one - this was exactly the issue, I think it's a design change as the OEM originals I took off in October have circlipped-on heads to valve stems, this one is screwed and snapped off around the middle of the thread.On my old 3.6TDV8 it was running s
te and I put it into my local specialist. They checked it all out, no error codes so suspected turbos were on way out. Swapped both, made no difference although old ones were starting to go.Much head scratching, no obvious reason what the problem could be. Eventually they started a strip down to try and find something wrong and had their eureka moment when they took of the EGR valves... one of them was missing the end of the valve stem. The car thought the valve was operating as expected, the garage had been able to hear it operating as normal, but it just wasn't sealing (or opening) as it should have done, effecively it was just wide open all the time.
My paperwork for the car showed that the EGRs had been replaced by the previous owner several tens of thousands of miles previously, but he hadn't used JLR EGRs, he'd got some cheapies from China, and the valve head had just snapped off.
Made the car run like a b
h, chugging and smoking all over the place.Found it exactly as in the pic when I removed it from the cooler.
This was the smoke level while it was broken, hopefully someone else will find this thread and avoid expense and head scratching!
Edited by Krikkit on Tuesday 25th July 21:44
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