andyfreelandy said:

@Ross Tait Thanks for the like ! Any idea why there should have been a delay on all coming good after fitting new O2 ?? Thanks

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Given when you put the new o2 sensor in that as you described problem 1 was gone and the fuel trims looked fine to me I would suspect reason number 2 above.
The only thing I noticed slightly different between your new o2 sensor reading vs your old known good was the switching rate. There was a lot more up down happening but I guess that could just be accounted for by the fact that this is a new o2 sensor and your known good may have been not brand new? Maybe that’s the only reason for the difference I saw.

We often have to drive cars a few miles at work to get warning lights and fault codes to bugger off after repairing stuff even if we’ve tried deleting the fault codes. I think the cars just need to be convinced themselves via self testing that it’s actually fixed before they’ll remove certain fault codes and extinguish warning lights.

Thanks. Usually clearing the fault code does the trick, but this wouldn't clear until it was happy !!

Vehicle has been fine, but used for short runs. Took it out today and all good until fully warmed up. Then it starts to 'cut' whilst driving. No ignition lights, no stalling. Tickover is fine. It just does a big 'miss' when driving, enough to jerk you about.

Capture one said 'miss' on my O2 sensors scan. They both dive to 0V.

So the bug is still there even though the new O2 sensor has cured the problem with the fuel trim traces.

I think the trace, attached, purely shows that the engine stops (just to left of centre) That bit I know !! Any ideas?? Will try to confirm it is only when warmed up or whether it is random.

Thanks.

andyfreelandy said:

Vehicle has been fine, but used for short runs. Took it out today and all good until fully warmed up. Then it starts to 'cut' whilst driving. No ignition lights, no stalling. Tickover is fine. It just does a big 'miss' when driving, enough to jerk you about.

Capture one said 'miss' on my O2 sensors scan. They both dive to 0V.

So the bug is still there even though the new O2 sensor has cured the problem with the fuel trim traces.

I think the trace, attached, purely shows that the engine stops (just to left of centre) That bit I know !! Any ideas?? Will try to confirm it is only when warmed up or whether it is random.

Thanks.View attachment 304066

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Hi there, ok so seems your almost there with it. Often many things can be worn out and collectively making it run less well than desired.
If I’m interpreting the pic data correctly then it looks like the o2 sensors dropped to 0v for around 3 seconds.
There could be a number of electrical reasons for that happening. If it was just the old o2 then I may suspect it’s just old and duff.
But because the new sensor dropped out too I’d be more inclined to think they may have lost power or ground momentarily or there could be a bad connection somewhere. I’ll go have a look at the wiring diagram tomorrow and see what the two both have in common.
Could even be a frayed wire in the harness going short to ground momentarily when you went over a bump for example.
You could try jiggling the harness whilst watching live data to see if anything happens.

Thanks, yes, or maybe something else stopped the engine like fuel starvation which would cause a zero O2 output too?? It is a cause and effect problem I fear.

Looked out the relevant fuse links, main relay etc and tightened / cleaned / checked / substituted. No change.

Once warm can hold at 3k rpm and it drops randomly to about 1k rpm and doesn't pick up again until fault clears.

I think fuel pressure is next. Can't see how a warm engine makes it worse??

Also, had all plugs out and did a compression test again whilst hot. 175, 150, 150, 175 PSI.

So no worse when warm.

Might also go out for drive with Pscan data logging to have a look at what is happening. Hard to know what to monitor though as it appears everything crashes for a few seconds. Difficult one this. Identifying the cause rather than the effects is tricky.!!

andyfreelandy said:

Looked out the relevant fuse links, main relay etc and tightened / cleaned / checked / substituted. No change.

Once warm can hold at 3k rpm and it drops randomly to about 1k rpm and doesn't pick up again until fault clears.

I think fuel pressure is next. Can't see how a warm engine makes it worse??

Also, had all plugs out and did a compression test again whilst hot. 175, 150, 150, 175 PSI.

So no worse when warm.

Might also go out for drive with Pscan data logging to have a look at what is happening. Hard to know what to monitor though as it appears everything crashes for a few seconds. Difficult one this. Identifying the cause rather than the effects is tricky.!!

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Hi there, I’ve had a bit of time to think about it and yea I agree it could be an electrical circuit or it could be actual lambda readings.
It’s good you’ve got started on basic checks already as you’ll find the answer sooner.

So here is what I make of it. The problem is gonna be down one of the above paths, either the lambda sensors have a circuit fault or the system actually went fully lean for a few seconds.

Step 1:
So we need to know which. To test the lambda circuit power and ground you could easily set up two separate circuits using w5w bulbs or test lamps. One taking power from lambda power supply and earthing not via lambda circuit and the other one taking power not from lambda but earthing to lambda circuit earth. Re create the problem and observe the bulbs when the cut out happens, if both bulbs stay lit then power and ground are ok and move on to step 2. If one of the bulbs go out during cut out then you’ll know it’s power/ground issue and from which bulb went out will tell you whether power or ground was the problem.

Step2:
If the lambda values from the live data during cut out are correct and the system just went fully lean then you may already have an indicator. In my experience a fuel miss is usually what I call a soft misfire and an ignition miss is usually a hard misfire. Just the feeling of driving it and the cut out jerk being either soft or hard can be useful information so try that and take the answer info forward with you in the diagnostic.

If the system is going fully lean there is many things that could cause this and so anything involved with the following is suspect;

FUEL DELIVERY;
Fuel pump
Fuel filter
Fuel pressure
Fuel Injector power supply
Crank/cam sensors
Throttle position sensor

AIR INTAKE MEASUREMENT;
MAF
MAP

Start with observing the above suspects on live data and see if anything drops out. You will need to use a test light or bulb and take its power from injector power supply and earth to battery in order to easily monitor injector power supply.
If the fuel rail has a schrader valve then you can connect a cheapo fuel pressure tester to there for that data. Those and the usual live data should cover it all. Your looking for something tps map etc dropping out momentarily.

Don’t wanna write a book so I’ll leave it there for now, see if you find anything in the above. And btw if it was ign sys misfire it would go rich so forget ign for now.

Cheers

Many thanks. Really helpful. It feels like power to something is cut momentarily.
Will pursue investigation. It will be one of those "obvious when found" faults !!

Actually, seeing what happened at static revs, it is hard without fixing the throttle somehow but the revs fell and not sure they went back, to where they were. So TPS is a possible. Not sure of how it works on the 1.8. There is a throttle cable but I think a hall effect sensor too. Will research.....

andyfreelandy said:

Many thanks. Really helpful. It feels like power to something is cut momentarily.
Will pursue investigation. It will be one of those "obvious when found" faults !!

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No problem matey. It’s good brain exercise for me anyway. Was off work the last 9 months and just back a week ago so I’m a bit rusty anyway and need sharpening up.

We cracked it ! Finally and thanks for all the help and support.
Very odd fault. It displayed the following characteristics.
Lack of power on hills.
No cut out at about 3k rpm when 1st O2 sensor was fault, but when O2 sensor changed and fuel trim corrected then the fault appeared.
When driving it would 'kick' and feel like you cut the engine for a few seconds at about 3k rpm.
No fault codes, no stalling, no idle issues.

Got the vehicle to do it whilst stationary. Hold rpm at about 3k and it dropped to 1k and with foot steady it didn't return to 3k until remove foot and re rev up again.
Had a couple of instances of orange HDC lamp but changed brake switch and this went away.

The 1.8 Freelander has a Hall Effect sensor on the accellerator pedal and a Throttle Position Sensor (TPS) on the throttle body.

With all the help and support I concluded that it was most likely one of these 2 items.

When I drove into the workshop this morning I used no throttle and the orange HDC light came on.

Ok, took a spare TPS and inspected it. It is basically a 3.9K ohm potentiometer and has 3 connections and is a variable resistor. The outside 2 terminals gave 3.9k ohms and the centre slider gave 200 ohms to 3.9k ohms as they should wrt the centre pin.

When I removed the TPS from the vehicle with the problem, it was open circuit across the outside pins, open circuit in one direction and was open circuit until halfway and then cut in at about 3k ohms in the other. So I think the vehicle was happy, but not right, with an open circuit and when the resistance kicked in it 'cut out' whilst regaining its position and settings.

Changed the TPS. Problem solved. Power back on hills (as much as a 1.8 Freelander should have!) And no more hesitations.

Gave it a gentle warm up run then pushed it a bit to clear the old unburnt gasses etc.

I learned 2 things;

1. General Grabber AT s are scary in the wet.
2. There is a dark mix of particles in the coolant tank after a hard drive. Not oil but black and copper coloured flakes. See another thread !!!

Cheers to all...

andyfreelandy said:

We cracked it ! Finally and thanks for all the help and support.
Very odd fault. It displayed the following characteristics.
Lack of power on hills.
No cut out at about 3k rpm when 1st O2 sensor was fault, but when O2 sensor changed and fuel trim corrected then the fault appeared.
When driving it would 'kick' and feel like you cut the engine for a few seconds at about 3k rpm.
No fault codes, no stalling, no idle issues.

Got the vehicle to do it whilst stationary. Hold rpm at about 3k and it dropped to 1k and with foot steady it didn't return to 3k until remove foot and re rev up again.
Had a couple of instances of orange HDC lamp but changed brake switch and this went away.

The 1.8 Freelander has a Hall Effect sensor on the accellerator pedal and a Throttle Position Sensor (TPS) on the throttle body.

With all the help and support I concluded that it was most likely one of these 2 items.

When I drove into the workshop this morning I used no throttle and the orange HDC light came on.

Ok, took a spare TPS and inspected it. It is basically a 3.9K ohm potentiometer and has 3 connections and is a variable resistor. The outside 2 terminals gave 3.9k ohms and the centre slider gave 200 ohms to 3.9k ohms as they should wrt the centre pin.

When I removed the TPS from the vehicle with the problem, it was open circuit across the outside pins, open circuit in one direction and was open circuit until halfway and then cut in at about 3k ohms in the other. So I think the vehicle was happy, but not right, with an open circuit and when the resistance kicked in it 'cut out' whilst regaining its position and settings.

Changed the TPS. Problem solved. Power back on hills (as much as a 1.8 Freelander should have!) And no more hesitations.

Gave it a gentle warm up run then pushed it a bit to clear the old unburnt gasses etc.

I learned 2 things;

1. General Grabber AT s are scary in the wet.
2. There is a dark mix of particles in the coolant tank after a hard drive. Not oil but black and copper coloured flakes. See another thread !!!

Cheers to all...

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Glad you got it sorted matey. With how the tps potentiometer works the ecu may have interpreted the 0v as minimum throttle or less. That would give the fuel cut as it may think foots off the gas to slow down. That one was a good brain teaser .

She is running well. Flushed and refilled coolant.with fresh antifreeze and all clean and no water useage.

ONLY when cold, for about 2 mins, if clocks a misfire cyl 3 fault code. EML blinks. Once warm all is well.

Have replaced coil packs, plugs no change.
How does the ECU register a misfire? Is it purely detecting electrics or could it detect a faulty injector?

Thanks.

andyfreelandy said:

She is running well. Flushed and refilled coolant.with fresh antifreeze and all clean and no water useage.

ONLY when cold, for about 2 mins, if clocks a misfire cyl 3 fault code. EML blinks. Once warm all is well.

Have replaced coil packs, plugs no change.
How does the ECU register a misfire? Is it purely detecting electrics or could it detect a faulty injector?

Thanks.

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Hey, glad your nearly there. As for the misfire count I believe that most of them analyse the crank sensor waveform as it can detect even slight or momentary reductions in rpm. I would say that given it’s a wasted spark ignition system, and assuming it’s an ignition misfire then by default it has to be either the spark plug or the ignition lead.

Cheap plug coils or leads, even brand new cam cause this.

I would test with known good and also double check the lead to coil contact is tight and moisture free.

You could also monitor fuel injection pulse on no 3 cylinder using a basic led or suitable test pen. Just to be sure your not loosing injector pulse momentarily.

As above.
The ECM counts pulses using the crank sensor. It's able to detect minute fluctuations in RPM, which allow the ECM to say what cylinder is given less power than the rest.
It could be low compression related, as 150 PSI is below the minimum I'd expect to see.

Thanks. Pscan shows the same injector duration across all 4. That doesn't mean that they are mechanically opening though.

I will subs the original coil pack back as I changed it to eliminate while looking for the TPS fault. Think it was an ok pack.

I think it clears too quick for compression problem. Also drives too well. Will do a cold and hot compression test to see if worse.

Cyl 3 has the coil pack fitted so no ign lead. The spring is tight on the plug.

andyfreelandy said:

Thanks. Pscan shows the same injector duration across all 4. That doesn't mean that they are mechanically opening though.

I will subs the original coil pack back as I changed it to eliminate while looking for the TPS fault. Think it was an ok pack.

I think it clears too quick for compression problem. Also drives too well. Will do a cold and hot compression test to see if worse.

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Hey, the injector duration is likely just the ground side pulse so would likely read the same whether it was working or not. I’d do the light test as it’s quick, easy and free.
Yeah if this issues appeared since a coil pack change then I’d swap it back and see what happens. Or swap cylinders to see if fault moves with it.
Compression would probably go up as the engine heats so the hot and cold compression tests are a good idea.
Yeah I was thinking after I posted that, I couldn’t remember which cylinders had the coil over and which had the lead.

So changing the plug 3 coil pack which also feeds plug 2 has removed the problem. For now !!
Watch this space. Hard to see how it wouldn't cause a cyl 2 & 3 misfire but there we go, not sure how they are manufactured, seperate windings for the 2 outputs?