L series idle issues

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Bluey89

Bluey89

Member
Posts
66
Location
Cornwall, UK
Although I've found various bits of info online, they are all from very old threads. Any help would be gratefully received. Below is detailed the symptoms.

Likes to randlomly idle at 1100 rpm
Very rarely returns to normal
Idle randomly rises and lowers them settled, almost like the ECU is playing arou d to optimise fueling.

Idle sometimes randomly rise to 2000 rpm, only way to cure is ignition off then on.
This happens whilst at standstill, handbrake on. No input on any controls.

Whilst cruising under very slight throttle input, complete loss off power with CEL indication. Can happen once, or multiple times (kangaroo effect).

My first thought was the throttle potentiometer but have read about people replacing these to no avail.
O2 or MAF issues?
Anything I'm missing?

Many thanks in advance
Luke H
 
I don't think the MAF is used on the L Series once it started - but don't take my word on it.

My thoughts were the TPS as well - maybe you could plug a Hawkeye or iCarsoft in to see what the ECU is getting from the TPS - will definitively tell if that's at fault.

You could check wiring from ECU to fuel pump - give connections a clean.
 
I was under the impression that the MAF gave a constant reading for IAT etc. There are no other sensors for temp other than coolant so the MAF would be the only source for IAT that I can think of. Again please correct me if I'm wrong
 
C
GrumpyGel said:
Yeh, I got that round the wrong way didn't I!

In that case, I think you can unplug it and the ECU will use default settings. If it still 'hunts' then it can't be the MAF.
Click to expand...
Cheers. Didn't realise that it used default. I'll try that on the drive home from work
 
Hi, no, on the L series the IAT is on the inlet manifold - NOT on the MAF - the MAF does Jack Sh!t apart from control the EGR which is better removed.

Sounds like it could be a stuck . sticky egr - dump it then blank it - also then throw away the maf and fit a tube.
No 02 sensor - EML on L series tends to indicate the VP37 pump variable solenoid for the mixture is out of whack (the light only tends to come on when the commanded pwm position is not reached via the closed circuit feedback loop.)
Sounds like an air leak on the induction - probably egr -
The ECU is basic, it looks at TPS, speed (RPM and road) mixture solenoid position etc -
Could well be tps but this would usually log a fault in the ECU (DCU) - read codes and check ! - mixture warning (eml that comes on and goes off depending on load!) tends to indicate either a leak - - or, a stuck or malfunctioning solenoid on the VP37 - or, if you have just got the vehicle - someone has incorrectly fitted the timing belt to the pump - or removed the pulley to the pump without using the shaft locking tool.

IF you have just got the vehicle - OR have had the pump timing belt changed then I would be extremely cautious !!!!. very very common issue where so called 'mechanics' believe the pully is 'keyed' to the fuel pump spindle - it is NOT - also, many do not understand even the basics of the simple locking of the position for the pump drive v cam drive leading to a real mess.
:)
Joe
 
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Joe_H said:
Hi, no, on the L series the IAT is on the inlet manifold - NOT on the MAF - the MAF does Jack Sh!t apart from control the EGR which is better removed.

Sounds like it could be a stuck . sticky egr - dump it then blank it - also then throw away the maf and fit a tube.
No 02 sensor - EML on L series tends to indicate the VP37 pump variable solenoid for the mixture is out of whack (the light only tends to come on when the commanded pwm position is not reached via the closed circuit feedback loop.)
Sounds like an air leak on the induction - probably egr -
The ECU is basic, it looks at TPS, speed (RPM and road) mixture solenoid position etc -
Could be tps but this would log a fault in the ECU (DCU) read codes and check ! - mixture warning (eml that comes on and goes off depending on lad!) tends to indicate either a leak - - a tuck or malfunctioning solenoid or, if you have just got the vehicle - someone has incorrectly fitted the timing belt to the pump - or removed the pulley to the pump without using the shaft locking tool.
Joe
Click to expand...
Thank you very much. I've had the LR about a year now with the erratic idle for a good proportion of that. Just kind of learnt to deal with it. I've got it going into a LR specialist next week for a new clutch and glow plugs and asked him the read the codes whilst he's at it. Before I do that I'll remove the EGR and blank it just to remove that from the equation. I honestly didn't realise the MAF only controls the EGR. I thought it ran off vacuum.
 
Bluey89 said:
Thank you very much. I've had the LR about a year now with the erratic idle for a good proportion of that. Just kind of learnt to deal with it. I've got it going into a LR specialist next week for a new clutch and glow plugs and asked him the read the codes whilst he's at it. Before I do that I'll remove the EGR and blank it just to remove that from the equation. I honestly didn't realise the MAF only controls the EGR. I thought it ran off vacuum.
Click to expand...
Hi Mate, yes, the EGR DOES run off vacuum - however - the vacuum is PWM controlled (Hence variable) via the ECU to the EGR actuator on the bulkhead. The egr position is constantly variable via this method - of course - unless it is stuck ! :)
you could try unplugging the supply to the EGR solenoid ... however - this would only work if the EGR valve is fully closed - it will keep the valve closed as no PWM signal is sent to the EGR actuator to vary the (relatively) 'constant vacuum INPUT' from the alternator front driven vacuum pump. This vacuum does not pass directly to the EGR - it is controlled and reduced via the PWM valve unit.
Hope that helps ?
Just pray someone has not removed the fuel pump without using the lock nut unit on the shaft !- nightmare :) ... but unlikely.
Sticking mixture solenoid on the bottom of the VP37 is a known issue - however, with the varying idle this sound like a possible intake leak ???
Joe
 
I doubt it is the belt that's wrong. If the belt gets slack or is fitted incorrectly they become a bugger to start. Also it won't change, it'll be wrong full stop, won't go back to proper idle.

I'm also inclined to think its not the EGR actuation - ie not getting stuck open or shut. The EGR should be at it maximum opening when at idle and then closes as the revs increase and more oxygen is needed. If its stuck shut then that's the same as blanking the EGR and if its stuck open it will only affect it as the revs increase.

I there was an air leak in the induction, I'm not sure how much this would affect idle? I'm sure it would also be throwing out lots of excessive smoke.

I'd still check the TPS readings on a code reader - it'll be easy to diagnose and fix.

Give the wiring contacts on the pump a clean first, once again quick and easy. As said though could actually be a fault with it (solenoid).
 
MAF is only there to monitor air flow to keep the mixture correct while the EGR is passing exhaust into the engine. The ECU couldn't know how much fuel to inject without it. However if the EGR is blanked, the MAF signal becomes redundant;)
Idle issues must surely due to the feedback resistor in the fuel pump solonoid unit.
Air leaks wouldn't matter because a diesel is at WOT anyway and there's no throttle butterfly to impede air flow. This is why I think it's a throttle position feedback issue.
 
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I'm still trying to understand why the MAF becomes redundant upon EGR delete. Surely the ECU still requires a reference point for fuel/air mixture? Or have I got this completely wrong. My expertise is from a jet engine background. Diesels are not my speciality.

If it helps I've removed and plugged the EGR vacuum hose a couple of weeks ago until I get blanking plates with no change on the issue I hand. Although this is reliant on the EGR being fully serviceable.

Saying that, she did seem to behave on the way home, which although initially is good, is also frustrating because I want the issue to be there when it goes into the LR specialist next week.
 
I've got her going into a garage for a new clutch, ARB drop links, glow plugs (which are currently siezed) and I've requested a full diagnostic. I supply the parts, he is charging me £300 labour with a courtesy car for a couple of days :D

Fingers crossed I get a healthy freelander back
 
The L series ECU isn't a very clever or complex unit. A diesel engine in its most basic form is throttled by the amount of fuel injected. So more fuel in = more power out.
This is why diesel engines are so fuel efficient by comparison to an equivalent size and power petrol engine.
So being that the more fuel = more power, at idle the amount of fuel injected is minute. Or you could say that the mixture is extremely lean.
Due to the high compression of a diesel, combustion temperatures are high. This leads to the production of NOx emissions which is controlled by legislation. The only way to control high combustion temperature is to replace some of the oxygen in the cylinder with an inert gas. The engine just happens to make lots of inert gas in the form of CO2 in the exhaust.
So under ECU control, at set points in the operating cycle, the ECU allows exhaust gas into the inlet tract. This has the effect of reducing the oxygen and so combustion temps. The ECU monitors how much exhaust is entering the engine by the reduction of air measured by the MAF. The ECU can then reduce the fuel volume accordingly, to prevent black smoke from being produced.
So blanking the EGR means the MAF doesn't see a reduction in air, so no leaning of mixture will take place.
From memory, the ECU only refers back to the MAF signal, while the EGR valve is open.
 
Nodge68 said:
The L series ECU isn't a very clever or complex unit. A diesel engine in its most basic form is throttled by the amount of fuel injected. So more fuel in = more power out.
This is why diesel engines are so fuel efficient by comparison to an equivalent size and power petrol engine.
So being that the more fuel = more power, at idle the amount of fuel injected is minute. Or you could say that the mixture is extremely lean.
Due to the high compression of a diesel, combustion temperatures are high. This leads to the production of NOx emissions which is controlled by legislation. The only way to control high combustion temperature is to replace some of the oxygen in the cylinder with an inert gas. The engine just happens to make lots of inert gas in the form of CO2 in the exhaust.
So under ECU control, at set points in the operating cycle, the ECU allows exhaust gas into the inlet tract. This has the effect of reducing the oxygen and so combustion temps. The ECU monitors how much exhaust is entering the engine by the reduction of air measured by the MAF. The ECU can then reduce the fuel volume accordingly, to prevent black smoke from being produced.
So blanking the EGR means the MAF doesn't see a reduction in air, so no leaning of mixture will take place.
From memory, the ECU only refers back to the MAF signal, while the EGR valve is open.
Click to expand...
Thank you very much. That is a great help. I think an EGR + MAF delete are on the cards. No related problems for the future.

I keep thinking the whole issue stems from the throttle potentiometer, although I've read about other people with similar issues thinking the same thing, ended up being wrong with a lovely bill. I'll look forward to a long list of fault codes next week
 
GrumpyGel said:
I doubt it is the belt that's wrong. If the belt gets slack or is fitted incorrectly they become a bugger to start. Also it won't change, it'll be wrong full stop, won't go back to proper idle.
Click to expand...
Correct :) - I think the afternoon 'barbie' cold beer due to the heat (of course) affected my brain :rolleyes:

Nodge68 said:
Air leaks wouldn't matter because a diesel is at WOT anyway and there's no throttle butterfly to impede air flow. This is why I think it's a throttle position feedback issue.
Click to expand...
As above - doh :oops: Too hot to drink beer, cook burgers and confuse petrol / diesel intakes....

On looking again at what you say then I would also agree on the most likely diagnosis being TPS.

The engine doesn't use MAF for anything apart from EGR. All other fuelling is directly based on Crank position sensor (engine speed) and TPS. both static and the delta increase or decrease. Other adjustments to the basic maps are determined by inputs to the ecu from various sensors (ECT / FTS / MAP etc)

Other issues that commonly illuminate the mil light whilst running but do not fit your description completely (but without a total loss of power) are map sensor issues which will illuminate the light and drop the injection quantity to a preset limit (limp mode) and also the feedback loops from the fuel pump - the injection quantity and commencement of injection solenoids. If these cannot achieve commanded position then the mil light will illuminate for the duration of the issue then extinguish. The above is simply for reference and not related imho - to your issue..

However ! - the TPS has an idle 'switch' built in for idle command sensing. If a failure is detected (that follows certain criteria such as the voltage measurement from the wiper of the TPS after the throttle moves 9 degrees and idle switch closes - for example) then the rpm is set to a preset 1060 rpm and ac inhibited - along with mil illumination -1060 is extremely close to the 1100 rpm you are seeing !. - if an issue with TPS is sensed on the road - mil light on and power loss. Sounds familiar ?.
The L series is a relatively simple engine to diagnose but is a superbly designed unit with excellent performance and economy. It's apparant 'basic ECU / DCU 'simplicity' is actually extremely efficient.
Joe
(No barbecue today - :D)
 
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Bluey89 said:
I've got her going into a garage for a new clutch, ARB drop links, glow plugs (which are currently siezed) and I've requested a full diagnostic. I supply the parts, he is charging me £300 labour with a courtesy car for a couple of days :D

Fingers crossed I get a healthy freelander back
Click to expand...
Just as a tip - I would definitely recommend that on the L series you fit a PROVEN OEM clutch of a known make from a WELL known source / supplier (Rimmer or similar)- Not a cheap one or 'aftermarket' one. The clutch takes a real hammering on the L series around 1700 - 2200 rpm as the turbo comes on. An OEM or Original will give you no worries. The cheapo 'aftermarket' are usually total bollox. Also watch out for any signs of oil / black slime mixed with friction material etc - in the bell housing. The rear crankshaft oil seal has been known to leak causing issues and clutch slip / judder. The seal comes complete with frame and fitting sleeve. A good check of the release mechanism is also needed to ensure full and free movement as they are known to partially sieze. - You are probably aware of the above, however, if not I hope it is helpful.
Joe
 
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Bluey89 said:
Thank you very much. That is a great help. I think an EGR + MAF delete are on the cards. No related problems for the future.

I keep thinking the whole issue stems from the throttle potentiometer, although I've read about other people with similar issues thinking the same thing, ended up being wrong with a lovely bill. I'll look forward to a long list of fault codes next week
Click to expand...
Hi Luke - just out of interest, the TPS can be had for very little money at the breakers yard. Very few actually go wrong at all. Getting a used unit from a breakers is hence not an issue at all.
Joe
 
Joe_H said:
Just as a tip - I would definitely recommend that on the L series you fit a PROVEN OEM clutch of a known make from a WELL known source / supplier (Rimmer or similar)- Not a cheap one or 'aftermarket' one. The clutch takes a real hammering on the L series around 1700 - 2200 rpm as the turbo comes on. An OEM or Original will give you no worries. The cheapo 'aftermarket' are usually total bollox. Also watch out for any signs of oil / black slime mixed with friction material etc - in the bell housing. The rear crankshaft oil seal has been known to leak causing issues and clutch slip / judder. The seal comes complete with frame and fitting sleeve. A good check of the release mechanism is also needed to ensure full and free movement as they are known to partially sieze. - You are probably aware of the above, however, if not I hope it is helpful.
Joe
Click to expand...
In regards to the clutch, I have sat waiting for me to pick up tomorrow a Sachs clutch kit which I sourced through Eurocarparts. As far as I'm aware this should be absolutely fine, unless I'm wrong in which please say as it's not paid for her and can still walk away hahaha.

Want aware of the oil seal issue which is of NO surprise as originally stated. Diesels are not my area of expertise, her engines are, but the wealth of info you guys have given me is great. I'm loving the L series simplicity.
 
Forgot to mention last night after my daughter went to bed and with limited daylight remaining. ......I stripped the air intake manifold off and thoroughly cleaned it, completely isolated the EGR and fiddled with various wires on the HP injector pump. Removed the MAF and shock horror. ....today and I don't know how I did it or what cured it but the car has behaved perfectly today :D
 
Morning Luke :)
Fingers crossed - hopefully you fixed it - could have just been the injection quantity solenoid wiring. - see what the diags say. .... lets hope ! - Nice one!

Regarding the clutch kit - Sachs - no worries - 100% - would be in my top 3 along with Borg & Beck and LR Original.
Joe
 
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