Hello,
I have a 3.9 discovery hich is running very rich on petrol, on gas it is fine. It is an older gas system, with no lambda or throttle inputs or that.
On either fuel, it idles a wee bit rough, is that common?
On petrol, i have changed the stepper motor, checked the resistance of the fuel and water temperature sensors and they are 5k and 9k. I have set the throttle pot as per rpi instructions and calibrated the air meter, disconnected the ecu for a wee while to reset it but with no joy. I have even changed the tune resistor to elimate the lambda probes but it is still very rich.
The fuel pressure is 28psi. I am undecided whether to change the ecu or the air meter - any other ideas? I swapped the plugs on the petrol temp and the water temp sensor but with no joy. Please help
3.9 Hotwire running rich
Moderator: phpBB2 - Administrators
only 28psi i thought they were meant to be around 36psi as standard.
have you tried another fuel reg???
and what is the fuel pressure when you rev it???
is it rich at idle? or while reving?
have you tried another fuel reg???
and what is the fuel pressure when you rev it???
is it rich at idle? or while reving?
Regards Tony C (COOPS)
MS2 V3.57 Ecu mapable efi and wasted spark ignition.
Procharger D1SC supercharger and Cossie RS500 Intercooler @ 14psi of Boost. 416 RWHP, (boost leak)
Forged 4.8 V8 kitted out with the dogs Cajones of parts.
Sponsored by: www.v8performanceparts.co.uk, www.interpart.biz, www.caprisport.com & www.baileyperformance.co.uk
MS2 V3.57 Ecu mapable efi and wasted spark ignition.
Procharger D1SC supercharger and Cossie RS500 Intercooler @ 14psi of Boost. 416 RWHP, (boost leak)
Forged 4.8 V8 kitted out with the dogs Cajones of parts.
Sponsored by: www.v8performanceparts.co.uk, www.interpart.biz, www.caprisport.com & www.baileyperformance.co.uk
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stephenmcdermott
- Newbie
- Posts: 4
- Joined: Sun Nov 19, 2006 8:25 pm
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Ian Anderson
- Forum Contributor
- Posts: 2396
- Joined: Sun Nov 19, 2006 9:46 pm
- Location: Edinburgh
Try disconnecting the battery for 30 seconds and reconnecting
It could have gone into save "get you home" mode and that is RICH
Ian
It could have gone into save "get you home" mode and that is RICH
Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.
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stephenmcdermott
- Newbie
- Posts: 4
- Joined: Sun Nov 19, 2006 8:25 pm
3.9 Hotwire running rich
Stephen,
Reckon I've got a similar problem - see my first post on another forum, and my last - which may also help you.
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First Post:
Discovery V8i (3.9 EFi) - Overfuelling
Help!
My Disco's V8 has turned into a fuel pump.
It startered running lumpy at low revs, woudn't pick up from tick-over very well and started to stall now and again - it also had a slight misfire at around 2,000-2,500 revs.
Its been to a 4x4 specialist and put on, what looked like to me, a very basic diagnostic tester.
They first thought it was the Lambda probes (strangely, even the though the test showed and imbalance between the sensors - one bouncing around 15 the other around 7) they said that they'ed tested the sensors and they were OK.
Next, at a shade under £400 they reckoned it could be the Airflow meter, a quick change out made no difference.
All else is OK, and the problem came on suddenly, like something let go.
If you can get it to start, and when it does, it tends to be first time, it can run quite well, especially if given a run - but not always!.
If it doesn't start first time, the overfuelling just make things worse, and you can't guarantee then if it will start at all.
I'm now facing taking to LR, as I reckon they might have a more comprehensive diagnostic test than this 'specialist' I've just been to.
But before I do, I thought I'd throw this one out there to the combined minds of the forum.
Cheers, and fingers crossed,
Ian
Today's Post (maybe the answer)
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Discovery V8i (3.9 EFi) - Overfuelling
Guys,
Progress Report
Whipped out the Bypass Air Valve (Haynes Description) or the Idle Control Valve (LR Description) at the rear of the Plenum Chamber, and it was black as the ace of spades, all sooted up, and looked like it wasn't seating.
I took off the whole assembly and checked the vacuum hoses all seemed OK.
So I cleaned the Air Valve and the Valve Seating within the assembly with Carb Cleaner and polished the valve head where it looked like it had scaled up a little, and re-assembled it.
QUESTION (For anyone that might know)
The valve itself didn't seem to have much travel on it, and the spring around the shaft looked to be as compressed as it could be (i.e it's natural, unenergised state seemd to be in the 'valve open' mode).
Energising it would seem whould push the valve out, into the seating and close the vacuum air path from the hose on the filter side of the butterfly to the plenum chamber. The purpose of the valve is to 'trick' the ECU to overfuel when there is load, on idle, to increase engine revs. It does this by allowing extra air to pass - so you'd think 'Valve Open' for that condidtion Valve Closed normall.
Thing is, reassembling the Valve in the housing, the valve was not closed, and you could blow through from the vaccuum hose spigot.
Testing the valve, with it connected and grounded to the block and switching the ignition on gave no movement to the valve, just as slight vibration when switching the ignition off.
Having said all that, the clean-up seemed to have worked and she started first time. The road test was good too, seemd much smoother.
However, I'm not entirely convinced that it was just 'gunk' in the valve causing the problem, and wanted to check it out against a good one, or find out, from someone who knows, what the idle state of the valve is (i.e is it closed - no blow through).
That was put paid when enquiring with LR parts that they don't do just a valve, only an assembly @ £102, and they can't order one in just for me to look at it and compare.
They also said that they never have this valve go wrong, hence none in stock.
I'd like to nail this one completely, but £102 is a bit of a gamble.
Over to the forum, it might help the guy on the V8 website with the same problem too.
Cheers,
Ian
Reckon I've got a similar problem - see my first post on another forum, and my last - which may also help you.
--------------------------------------------------------------------------------
First Post:
Discovery V8i (3.9 EFi) - Overfuelling
Help!
My Disco's V8 has turned into a fuel pump.
It startered running lumpy at low revs, woudn't pick up from tick-over very well and started to stall now and again - it also had a slight misfire at around 2,000-2,500 revs.
Its been to a 4x4 specialist and put on, what looked like to me, a very basic diagnostic tester.
They first thought it was the Lambda probes (strangely, even the though the test showed and imbalance between the sensors - one bouncing around 15 the other around 7) they said that they'ed tested the sensors and they were OK.
Next, at a shade under £400 they reckoned it could be the Airflow meter, a quick change out made no difference.
All else is OK, and the problem came on suddenly, like something let go.
If you can get it to start, and when it does, it tends to be first time, it can run quite well, especially if given a run - but not always!.
If it doesn't start first time, the overfuelling just make things worse, and you can't guarantee then if it will start at all.
I'm now facing taking to LR, as I reckon they might have a more comprehensive diagnostic test than this 'specialist' I've just been to.
But before I do, I thought I'd throw this one out there to the combined minds of the forum.
Cheers, and fingers crossed,
Ian
Today's Post (maybe the answer)
--------------------------------------------------------------------------------
Discovery V8i (3.9 EFi) - Overfuelling
Guys,
Progress Report
Whipped out the Bypass Air Valve (Haynes Description) or the Idle Control Valve (LR Description) at the rear of the Plenum Chamber, and it was black as the ace of spades, all sooted up, and looked like it wasn't seating.
I took off the whole assembly and checked the vacuum hoses all seemed OK.
So I cleaned the Air Valve and the Valve Seating within the assembly with Carb Cleaner and polished the valve head where it looked like it had scaled up a little, and re-assembled it.
QUESTION (For anyone that might know)
The valve itself didn't seem to have much travel on it, and the spring around the shaft looked to be as compressed as it could be (i.e it's natural, unenergised state seemd to be in the 'valve open' mode).
Energising it would seem whould push the valve out, into the seating and close the vacuum air path from the hose on the filter side of the butterfly to the plenum chamber. The purpose of the valve is to 'trick' the ECU to overfuel when there is load, on idle, to increase engine revs. It does this by allowing extra air to pass - so you'd think 'Valve Open' for that condidtion Valve Closed normall.
Thing is, reassembling the Valve in the housing, the valve was not closed, and you could blow through from the vaccuum hose spigot.
Testing the valve, with it connected and grounded to the block and switching the ignition on gave no movement to the valve, just as slight vibration when switching the ignition off.
Having said all that, the clean-up seemed to have worked and she started first time. The road test was good too, seemd much smoother.
However, I'm not entirely convinced that it was just 'gunk' in the valve causing the problem, and wanted to check it out against a good one, or find out, from someone who knows, what the idle state of the valve is (i.e is it closed - no blow through).
That was put paid when enquiring with LR parts that they don't do just a valve, only an assembly @ £102, and they can't order one in just for me to look at it and compare.
They also said that they never have this valve go wrong, hence none in stock.
I'd like to nail this one completely, but £102 is a bit of a gamble.
Over to the forum, it might help the guy on the V8 website with the same problem too.
Cheers,
Ian
The stepper motor doesn't "trick" anything, it simply lets are past the throttle. The air is metered and will have the correct fuel added exactly the same as if it had gone through the throttle butterfly.
I think you said that you don't have a throttle potentiometer. What happened to it? Surely it had one as standard? Otherwise, the throttle response will be rubbish.
If I were you I'd start by check the water temp sender for the ECU. The resistance should be roughly 5kOhms at zero Centigrade, halving for each 20C increase in temperature. Check that you get the right reading at normal running temperature. Make sure the sender you're measuring is the one for the ECU (injector style two-pin plug) not the one for the temperature gauge. The best way to measure it is at the ECU plug if you can get to it, because this confirms the wiring as well as the sender. The coolant temp sender is measured across pins 7 and 25, the fuel is across 32 and 25.
I think you said that you don't have a throttle potentiometer. What happened to it? Surely it had one as standard? Otherwise, the throttle response will be rubbish.
If I were you I'd start by check the water temp sender for the ECU. The resistance should be roughly 5kOhms at zero Centigrade, halving for each 20C increase in temperature. Check that you get the right reading at normal running temperature. Make sure the sender you're measuring is the one for the ECU (injector style two-pin plug) not the one for the temperature gauge. The best way to measure it is at the ECU plug if you can get to it, because this confirms the wiring as well as the sender. The coolant temp sender is measured across pins 7 and 25, the fuel is across 32 and 25.
Peter Humphries (and a green V8S)
GreenV8S
I'm not sure if you're responding to Stephen's original problem, or the post I made offering another avenue to persue.
You said:
The stepper motor doesn't "trick" anything, it simply lets are past the throttle. The air is metered and will have the correct fuel added exactly the same as if it had gone through the throttle butterfly.
I mentioned 'trick in my post but I'm talking about the Air By-Pass valve (Haynes Description) or as Land Rover call it the idle control valve.
And yes 'trick' is the expression used by Haynes in black and white.
This has been the one thing that has been changed out/looked at that has made any positive difference at all.
I am grateful to you for the testing spec for the Water Temperature sender, I'll check that as precaution.
Cheers,
Ian
I'm not sure if you're responding to Stephen's original problem, or the post I made offering another avenue to persue.
You said:
The stepper motor doesn't "trick" anything, it simply lets are past the throttle. The air is metered and will have the correct fuel added exactly the same as if it had gone through the throttle butterfly.
I mentioned 'trick in my post but I'm talking about the Air By-Pass valve (Haynes Description) or as Land Rover call it the idle control valve.
And yes 'trick' is the expression used by Haynes in black and white.
This has been the one thing that has been changed out/looked at that has made any positive difference at all.
I am grateful to you for the testing spec for the Water Temperature sender, I'll check that as precaution.
Cheers,
Ian
Sorry I didn't quote you, but this is what my comment is about:Ian Seale wrote: You said:
The stepper motor doesn't "trick" anything, it simply lets are past the throttle. The air is metered and will have the correct fuel added exactly the same as if it had gone through the throttle butterfly.
I mentioned 'trick in my post but I'm talking about the Air By-Pass valve (Haynes Description) or as Land Rover call it the idle control valve.
And yes 'trick' is the expression used by Haynes in black and white.
It doesn't trick the ECU to overfuel, it simply allows air to bypass the throttle butterfly which has a similar effect to you opening the throttle. The air is metered (the same as the air that passes through the throttle butterfly), so the ECU adds the corresponding amount of fuel to maintain the correct mixture.Ian Seale wrote: The purpose of the valve is to 'trick' the ECU to overfuel when there is load, on idle, to increase engine revs. It does this by allowing extra air to pass
The stepper motor is a notorious source of idle stability problems on TVRs because it gets sooted up so easily, but it's very simple in operation and the problems are not about the engine running lean or rich.
Peter Humphries (and a green V8S)
Discovery V8i (3.9 EFi) - Overfuelling
GreenV8S,
This has got quite confusing.
What Haynes calls an Air By-Pass Valve is what LR call an Idle Control Valve and what most people, it seems, seem to know as a Stepper Motor.
I checked with the manual, and Haynes use the word 'Fool' not trick but in essence its still the same - the valve open to allow air to by-pass and the ECU then delivers more, or overfuel as Haynes say. This is fine under idle conditions where extra load is aplied i.e in Drive, A/C, PAS etc.
But I considered, have had an Overfuelling condition which just came on, that if the valve where not operating properly, it could overfuel under 'normal' idle conditions - therefore making it hard to start and tickover, and mumpy at low revs.
Yes, the valve was really badly sooted up.
After cleaning it, and reassembling, the valve did not appear to seat (close) in its natural postion (ignition off, or on). I have not been able to check if that is 'Normal', but It did start first time, albeit in a lumpy way, with the vacuum hose compressed and blanked off (Simulating 'Valve Closed) - leading me to suspect that the valve must need to be closed or close to closed on start-up.
Problem is, despite running fine yesterday, she didn't start this morning.
I'd like to know what the valve's 'natural state' is, whether it has a range of travel, is simply open or closed, or open and partially closed.
Whe I removed te valve to clean it, it did not look like it had been 'seating'.
This has got quite confusing.
What Haynes calls an Air By-Pass Valve is what LR call an Idle Control Valve and what most people, it seems, seem to know as a Stepper Motor.
I checked with the manual, and Haynes use the word 'Fool' not trick but in essence its still the same - the valve open to allow air to by-pass and the ECU then delivers more, or overfuel as Haynes say. This is fine under idle conditions where extra load is aplied i.e in Drive, A/C, PAS etc.
But I considered, have had an Overfuelling condition which just came on, that if the valve where not operating properly, it could overfuel under 'normal' idle conditions - therefore making it hard to start and tickover, and mumpy at low revs.
Yes, the valve was really badly sooted up.
After cleaning it, and reassembling, the valve did not appear to seat (close) in its natural postion (ignition off, or on). I have not been able to check if that is 'Normal', but It did start first time, albeit in a lumpy way, with the vacuum hose compressed and blanked off (Simulating 'Valve Closed) - leading me to suspect that the valve must need to be closed or close to closed on start-up.
Problem is, despite running fine yesterday, she didn't start this morning.
I'd like to know what the valve's 'natural state' is, whether it has a range of travel, is simply open or closed, or open and partially closed.
Whe I removed te valve to clean it, it did not look like it had been 'seating'.
It normally parks in the fully open position when you switch off. (If you switch on, then switch off again you should be able to hear this.)
The base idle should be set so that the stepper motor doesn't run out of travel, so it may be that the stepper motor never completely closes the valve in normal use.
The base idle should be set so that the stepper motor doesn't run out of travel, so it may be that the stepper motor never completely closes the valve in normal use.
Peter Humphries (and a green V8S)
stephenmcdermott wrote:hello,
when revved it goes up to about 30, rich when idling and running at revs. Goes like a bat out of hell as well at the moment!
The way you're talking about fuel pressure going up and down makes me suspect you have the vac line disconnected. The fuel pressure should be set with the vac line disconnected in order to remove the effects of the manifold depression variation. The nominal fuel pressure is usually 2.5bar (36 psi) for the standard hotwire setup but could have been changed if the engine is non-standard. The nominal fuel pressure is with no vacuum, and is the highest you should ever see. If you have the vac line connected and the engine running you will normally see much less fuel pressure, typically between 7-14psi less at idle.stephenmcdermott wrote: I have changed the pressure to 36psi, still running rich
Peter Humphries (and a green V8S)
Peter (Green V8S),
Many thanks for that.
"It normally parks in the fully open position when you switch off. (If you switch on, then switch off again you should be able to hear this.)"
Yes, it looked fully open when I had it out (the spring was fully compressed). Also, I did connect it up and get the missus to switch the ignition on and off - it didn't move at all, but it did vibrate slightly when switched off (nothing on switch on).
"The base idle should be set so that the stepper motor doesn't run out of travel, so it may be that the stepper motor never completely closes the valve in normal use."
That may explain why it looked like it wasn't 'seating' then - also why a severely sooted up one may cause problems.
I managed to get mine started this afternoon, after several pulls, but as soon as it fired it ran like a dream, and would start again first time, every time.
I had to go to Hemel, so risked taking it on a run round the M25 - 1 hour 60 mile motorway run, no problems, engine felt real smoothe too.
On the way back the M25 was f*cked so I had the most dreadful stop-start journey back via the North Circular, which itself was badly congested.
The point is the journey back was mostly on idle, 2 hours of hair-tearing stop start - and the engine did not play up at all! smoothe as anything and idled like it could go on all day, even though it smelt, and the fuel gauge was telling me that it may still be overfuelling
Previous to my cleaning the Bypass Air Valve it was as lumpy as a bag of spuds, and prone to stalling.
So possibly half the problem cured.
But, it's still a b*gger to start from cold - I'm sure it's Idle/Fuel related, and may still be the Bypass Air Valve.
I hope that this may help Stephen too.
Many thanks for that.
"It normally parks in the fully open position when you switch off. (If you switch on, then switch off again you should be able to hear this.)"
Yes, it looked fully open when I had it out (the spring was fully compressed). Also, I did connect it up and get the missus to switch the ignition on and off - it didn't move at all, but it did vibrate slightly when switched off (nothing on switch on).
"The base idle should be set so that the stepper motor doesn't run out of travel, so it may be that the stepper motor never completely closes the valve in normal use."
That may explain why it looked like it wasn't 'seating' then - also why a severely sooted up one may cause problems.
I managed to get mine started this afternoon, after several pulls, but as soon as it fired it ran like a dream, and would start again first time, every time.
I had to go to Hemel, so risked taking it on a run round the M25 - 1 hour 60 mile motorway run, no problems, engine felt real smoothe too.
On the way back the M25 was f*cked so I had the most dreadful stop-start journey back via the North Circular, which itself was badly congested.
The point is the journey back was mostly on idle, 2 hours of hair-tearing stop start - and the engine did not play up at all! smoothe as anything and idled like it could go on all day, even though it smelt, and the fuel gauge was telling me that it may still be overfuelling
Previous to my cleaning the Bypass Air Valve it was as lumpy as a bag of spuds, and prone to stalling.
So possibly half the problem cured.
But, it's still a b*gger to start from cold - I'm sure it's Idle/Fuel related, and may still be the Bypass Air Valve.
I hope that this may help Stephen too.
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stephenmcdermott
- Newbie
- Posts: 4
- Joined: Sun Nov 19, 2006 8:25 pm
Cheers guys for all this,
I have changed that wee valve too and cleaned it etc, and yes it only seems to move a wee bit when tested. I havnt had the chance to change the air meter, does anyone have a err5198 5am air meter they can list on ebay for sale?
Going to give the valve a thorough clean, but dont hold out much hope for the running rich at all revs. Fuel pressure is 36psi all the time.
The car really shifts, but is totally guzzling the fuel and the unburnt fuel is on the dark side when coming out the exhaust!
On lpg, the car runs great, but still hunts a bit at idle!
I have changed that wee valve too and cleaned it etc, and yes it only seems to move a wee bit when tested. I havnt had the chance to change the air meter, does anyone have a err5198 5am air meter they can list on ebay for sale?
Going to give the valve a thorough clean, but dont hold out much hope for the running rich at all revs. Fuel pressure is 36psi all the time.
The car really shifts, but is totally guzzling the fuel and the unburnt fuel is on the dark side when coming out the exhaust!
On lpg, the car runs great, but still hunts a bit at idle!
