Flashing check engine light Discovery 3S 4.0 V6

[Julian B]

Hi folks. Now that I have organised paypal I am a paid up member!

I need some help regarding my Discovery petrol V6.
I bought this for a steal with a cooked gearbox and replaced the ageing but reliable forester.
It does half of its time on the highway between 80 and 100km/h so isn't just an airconditioned urban box.

I returned from a highway run and the morning after this I went to start it and promptly got a flashing check engine light (CEL), and an idle that was just decreased and a little rough feeling. I did not drive but a quick rev revealed a smooth sounding motor above idle.
I have a cheap OBD scanner, which shows faults:
P0300
P0301
P0303
P0305
P0316

This combination suggests a misfire on all cylinders on the driver's side bank. For others reading this in the future from other countries, with the hood/bonnet open and staring at the motor this would be on your left.
Standing behind the car it smells like fuel thus confirming a probable misfire.

My thoughts:
- Each cylinder has its own coil on this motor
- The oil looks good, no cream
- The coolant looks good no oily residue and there is no smell or steam ****ing out the exhaust
- Is it an electrical fault?
- Vacuum?
- Strong starter sound and no hesitation to starting

What have I done?
So I pulled the plugs. They looked original with a gap ~2.5mm but not black/green/burnt. Changed with genuine plugs and hard reset the same issue.
MAF sensor wire cleaned with CRC MAF sensor cleaner. No change.

Throttle body previously cleaned following a CEL.
Air filter replaced 3 months ago.

What causes a sudden change to a whole bank, without warning? I don't want to drive this to fry the catalytic converters, but side of the road revving at cold feels smooth so what is going on?

Thanks,

[MonLand]

Weird. But I would google the same symptoms since this is a Ford engine common used on a lot of trucks. For example: 4.2L V6 Misfire Mystery - Ford F150 Forum (https://www.fordf150.net/forums/viewtopic.php't=102923#p689518)

[bee utey]

A cylinder with a vacuum leak on the inlet side will still push out unburnt fuel, but only at idle. So probably safe for the short term. Failing inlet manifold gaskets are common on various engines and can usually be found by using a piece of hose as a stethoscope. If you can dribble some water along the manifold edge any sucking noises would lead you to the leak site too.

[Disco-tastic]

Don't they have individual ignition coils? Could it be a faulty coil or lead?

I don't know if you can do the "pull off a lead til you find the faulty cylinder" thing with the modern motors but would that be worth a try?

[PhilipA]

You maybe should google Explorer P0300. There are lots of instances there.
Here is one,


the p0300 code means multiple cylinder missfire. That could be the coil, but you have ruled that out. Next would be the cam sensor, bad or blocked EGR ports, or bad O2 sensor. Normally if its the O2 you will get that code. I might have a tendancy to check the cam sensor and EGR prior to looking into the CAT... but that is a possibility. Hopefully not on a 2004. Got bad gas in your area ??


Regards Philip A

[101RRS]

Just get the codes read by a proper machine and it will most likely tell you exactly what the issue is and what cylinder etc is playing up.

[Julian B]

A cylinder with a vacuum leak on the inlet side will still push out unburnt fuel, but only at idle. So probably safe for the short term. Failing inlet manifold gaskets are common on various engines and can usually be found by using a piece of hose as a stethoscope. If you can dribble some water along the manifold edge any sucking noises would lead you to the leak site too.

Gasket was a thought, and I like your observation about idle only. Sudden failure though?


Don't they have individual ignition coils? Could it be a faulty coil or lead?

I don't know if you can do the "pull off a lead til you find the faulty cylinder" thing with the modern motors but would that be worth a try?

Each cylinder has own coil... Sudden failure on whole bank.


You maybe should google Explorer P0300. There are lots of instances there.
Here is one,

Regards Philip A

Nice observation. Where are the sensors described here on the 4.0 engine in my car?


Just get the codes read by a proper machine and it will most likely tell you exactly what the issue is and what cylinder etc is playing up.

Anyone in Adelaide got one and can swing by a stranded enthusiast?

[Disco-tastic]

...Each cylinder has own coil... Sudden failure on whole bank...


Sorry, just to confirm, but its multiple cylinders that are misfiring on one bank? Not just a single cylinder?

I have the same motor so am following this in case I ever have the same issue :)

[Julian B]

Sorry, just to confirm, but its multiple cylinders that are misfiring on one bank? Not just a single cylinder?


All cylinders on the drivers side are misfiring per the codes.

[Julian B]

Where can’t one find a manual for this motor?

[Cambo_oldjaguar]

Flashing check engine light comes with excessive misfires, that's a standard thing.

My internet expert diagnosis is that the catalytic converter on that bank is choked up or collapsed.

But i've had a few cars with choked cats which caused misfires like this, so it's not a guess, it's speaking from experience.

[DiscoJeffster]

I would suggest a proper diag tool such as the IID would shed more light however Cambo above sounds like he’s on the money.

[Julian B]

I would suggest a proper diag tool such as the IID would shed more light however Cambo above sounds like he’s on the money.

I'd love to do this, but don't have one. Is there an Adelaide member that might loan/rent one prior to me finding one to purchase?


Flashing check engine light comes with excessive misfires, that's a standard thing.

My internet expert diagnosis is that the catalytic converter on that bank is choked up or collapsed.

But i've had a few cars with choked cats which caused misfires like this, so it's not a guess, it's speaking from experience.

I do like this idea, as in the absence of a manifold pressure/flow/EGR/HO2S/injector fault code then back pressure may be causing this. Also the sudden failure on a whole bank after a long drive supports this.

Given that it runs fine would I be safe driving this car?

I guess putting a pressure gauge on the upstream HO2S (O2 sensor) port might yield a high pressure if this was the error. Does anyone know if such a tool is available?

[Cambo_oldjaguar]

You can measure the pressure in each pipe and compare the differential pressure before and after the cat. The problem is that a collapsed or choked cat may flow enough gas at idle, but not at higher rpm under load, so how do you test under the right conditions?

In saying that, the last car I had with a collapsed cat you could actually feel the reduced flow just by putting your hand over each tailpipe with it sitting there idling.

[101RRS]

If it is a cat issue reading the codes will show this.

If no IID tool is at hand the car needs to get to an indy or even a stealer and have them read.

Garry

[letherm]

Anyone in Adelaide got one and can swing by a stranded enthusiast?

The site has a list of owners of diagnostic tools. Here's a link showing Adelaide members.

Members with Diagnostic Tools (https://www.google.com/maps/d/viewer'mid=1F36uYNhWz-pZz7p1gxZhFwCJg5U&msa=0&ll=-34.86424313326374%2C138.872208640625&z=9)

Martin

[Cambo_oldjaguar]

If it is a cat issue reading the codes will show this.

If no IID tool is at hand the car needs to get to an indy or even a stealer and have them read.

Garry

What's the code for a collapsed or choked catalyst?

[letherm]

I had a look at my PDF workshop manual.

This is a cut and paste of the P0301 code. It refers to cylinder 1. The others refer to other cylinders - P0302 to 2, P0303 to 3 etc. P0300 says "Random Misfire Detected -No sub type information"

135112

Martin

[Julian B]

You can measure the pressure in each pipe and compare the differential pressure before and after the cat. The problem is that a collapsed or choked cat may flow enough gas at idle, but not at higher rpm under load, so how do you test under the right conditions?

In saying that, the last car I had with a collapsed cat you could actually feel the reduced flow just by putting your hand over each tailpipe with it sitting there idling.

Astute observation re conditions for testing, which I will reflect on.


If it is a cat issue reading the codes will show this.

If no IID tool is at hand the car needs to get to an indy or even a stealer and have them read.

Garry

Local independent can't see it for a month.

[Julian B]

So I just used the OBDII interface on the cheap reader I have.

Interrogating the STFT (short term fuel trim) it appears to read -25% on bank 1. Coupled with misfires all on that side I would hazard a guess that the computer is compensating by enriching the mix on that bank for all cylinders, so the next question is why is this occurring?

To me the logical extension is a vacuum leak on that side, and from reading extensively it sounds like the likely culprit is the manifold gasket, though a sudden leak there seems unlikely unless the computer has been compensating for ages on a slow leak and only now shows a misfire. Alternatively one of the vacuum hoses has broken or come off, but this would need to be on the misfiring side only.

Curious though is the lack of error code saying too rich on that bank.

The only other culprit could be a faulty upstream O2 sensor sensing constant lean condition and ordering enrichment to compensate. I have a spare downstream O2 sensor as I bought a pair to replace the other side with a heater fault, but just didn't have time to replace a functioing part.

What do people think?

[Julian B]

Flashing check engine light comes with excessive misfires, that's a standard thing.

My internet expert diagnosis is that the catalytic converter on that bank is choked up or collapsed.

But i've had a few cars with choked cats which caused misfires like this, so it's not a guess, it's speaking from experience.

Of course mate, this experience isn't lost on me. Would you expect to see any codes specific to this, or the enrichment on the data?

[Cambo_oldjaguar]

-25% is negative, it's pulling all the fuel out of that bank that it can, this means it's being measured as too rich by the O2 sensor, one cause for it being too rich would be a lack of air coming in, because it can't get the exhaust gases out.

Your cat is toast for sure.

[Julian B]

Your cat is toast for sure.

Hmmm, this is a well reasoned position. It is a little odd that there is no error code being generated for catalyst efficiency.

Interestingly it starts well on open loop, then as soon as it heats up and runs closed loop the STFT/fuel trim goes mega negative (rich) then reverts to open loop within 30 seconds- presumably due to the misfire. It is odd that there is no code for the running rich condition.

Looks like I need to find a cat lady.

[bee utey]

Interestingly it starts well on open loop, then as soon as it heats up and runs closed loop the STFT/fuel trim goes mega negative (rich) then reverts to open loop within 30 seconds- presumably due to the misfire. It is odd that there is no code for the running rich condition.



This is a common symptom of a dirty oxygen sensor. Voltage that is applied to the heating element leaks into the sensor output showing up as extra rich. Moisture from combustion settles in the sensor for a short time making a conductive path with the dirt, until it heats up properly. The misfiring is actually from excessively lean mixtures. Try a new oxygen sensor before embarking on any major cat control programme.

[Cambo_oldjaguar]

Well to rule that out, swap the O2 sensors over to opposite banks, if the faults stay on that bank it's the cat, if they move to the other bank it's the sensor/s.

[Julian B]

Shame they are such pigs of things to get to.
Pre or post cat sensor most likely?
If I had a little camera scope I could peek down into the cat!

[bee utey]

Pre or post cat sensor most likely?


Pre cat of course, they control the mixture. Post cat just checks for correct cat operation.

Last year I had someone bring in a later model Hilux with pre and post cat sensors, his "mechanic" had told him he needed a new cat (because the codes said so). Turned out the plugs had not been changed since the ute was new (180K ago) and the resultant constant misfire just overloaded the cat. New plugs, cleared the codes and away it went.

[Julian B]

Pre cat of course, they control the mixture. Post cat just checks for correct cat operation.

Last year I had someone bring in a later model Hilux with pre and post cat sensors, his "mechanic" had told him he needed a new cat (because the codes said so). Turned out the plugs had not been changed since the ute was new (180K ago) and the resultant constant misfire just overloaded the cat. New plugs, cleared the codes and away it went.

Hmmm. So the plugs were average but replacement hasn’t changed anything. It isn’t running poorly except a slight bumpy idle which suddenly appeared on a morning start along with the codes.

Ill change the pre cat sensors and see if it fixes the problem.

[Cambo_oldjaguar]

I reckon you'll be doing this next;

https://www.aulro.com/afvb/images/imported/2018/01/762.jpg

[Tombie]

That will likely bite you on the arse...

You’ll need to then fit emulators to the post Cat sensor input lines or it will go into limp mode.

[Julian B]

When I have a spare minute I'll start swapping sensors and see what happens. I had a good look at the access today with the sensor tool. Man its ugly.

[Cambo_oldjaguar]

Double post

[Cambo_oldjaguar]

That will likely bite you on the arse...

You’ll need to then fit emulators to the post Cat sensor input lines or it will go into limp mode.
I replaced them with aftermarket cats, not no cats at all.

Also, you don't get limp mode with no cats, just codes.

Edit

And fiddling with the downstream sensors is not a good idea either, they are also used for fuel trims.

Get some vgood aftermarket cats and problem solved.

[Pedro_The_Swift]

so the fuel trim is adjusted by o2 sensors after the exhaust gas has been through the converters?

hmmm..

[Julian B]

Get some vgood aftermarket cats and problem solved.

Not sure if the forum allows this but I've had a look around and cant find a supplier for quality aftermarket cats. The dealer prices are eye watering.

[Cambo_oldjaguar]

so the fuel trim is adjusted by o2 sensors after the exhaust gas has been through the converters?

hmmm..
Yep, it's a thing with newer petrol engines on Jags and Land Rovers, other makes too.

https://www.aulro.com/afvb/images/imported/2018/01/801.jpg


Not sure if the forum allows this but I've had a look around and cant find a supplier for quality aftermarket cats. The dealer prices are eye watering.
Any half-decent exhaust shop would be able to supply them, just cut the old ones out, weld the new ones in.

A standard type, not a "sports" one with a low cell count. $500 each fitted would be ballpark.

[Julian B]

Ended up taking the car to a trusted independent.
Replaced O2 sensors and fault remains.
Camera scope down hole, cat is perfect.
Ignition all working, now new plugs and leads, and fault remains.

Ongoing misfire codes. No hardware codes.

Noise on right bank the boys are thinking timing chain stretch and misfiring because of this. They have seen it before.

Anyone heard of this?

[Cambo_oldjaguar]

I would cut the cat out, weld in a temporary section of pipe and see how it runs.

I'm two for two on my own cars with misfires under load caused by choked cats, and on the 2nd car the cats "looked good" from a visual inspection.

Not to mention the numerous other cars I've seen with the same problem.

How much is it gonna cost to cut out the cat and weld in a temporary pipe, vs pulling the engine down to check the cam timing and chains?

Isn't the timing chain for the right bank at the back of the engine?

[PhilipA]

Have a look at YouTube on replacing 4.0 Explorer timing chains.

There is one in Spanish AFAIR which shows how to do it , but there are lots of special tools required to do it properly.

There must be a Ford specialist somewhere who has all the gear.

The 4.0 l started as a 3.0 Essex v6 and had the OHC heads grafted on so some chains are on the front of the engine and some on the back.
A job not to be undertaken lightly.
On the plus side a full long engine was when I looked a couple of years ago only about USD2500 from a USA Ford dealer . It may be cheaper to buy a new engine than renew the timing chains.LOL
Regards Philip A
Engine Timing Set-Stock Melling 3-398S 0 | eBay (https://www.ebay.com/itm/Engine-Timing-Set-Stock-Melling-3-398S-0/162863259304?_trkparms=ao%3D1%26asc%3D201701051554 10%26meid%3Df9754c30d5674a5799ca97b46931320a%26pid %3D100705%26rk%3D1%26rkt%3D1%26%26itm%3D1628632593 04&_trksid=p2045573.c100705.m4780)

[Julian B]

Yep the right hand one is at the back of the engine. Needs to be removed (engine) to get to repair.
There is a strong clatter once dropping back to idle from a hard rev- noted by the mechanic but obvious once done in front of me, but also notable at idle subtley.

Ugh, I am so conflicted about what to do.

There is misfire from startup, not just under load, and all on that bank.
The O2 sensors are working- replaced with DENSO units just in case, and they are not signalling poor cat efficiency.

I want it to be the cat, but the rattle and lack of codes to indicate this point away from this. I am loathe to spend more cash though.

Replacement motor with 110,000 is $5-6k installed locally. Rebuild $9k installed.

[Disco-tastic]

Sorry Julian, I can't help, but may I ask how many kms the motor has on it?

[Julian B]

200,000km mate.
I just can't reconcile the absence of any code indicating a cam/crank timing mismatch that would be enough to cause a misfire.
I might take it home and play investigator myself.

[Globetrotter]

Rereading the thread, your codes indicate a "misfire". Now a misfire can be heard, and felt by the engine rocking etc so do you actually hear it misfire as you indicate it is smooth when revved and to be smooth all cylinders are working.
The ECM controls spark based on Engine load, Engine temperature, The knock control function, On automatic transmission models, the shift control function, The idle speed control function.
You changed the gearbox and the shift control is an input to the ECM. If a cat is blocked it can be felt at the exhaust with your hand over the exhaust outlet
Just trying to understand the problem, Is fuse 17E in the battery box good as this powers the capacitor for the ignition

[Julian B]

There is a feeling of misfire, though not rough running condition, except maybe arguable at idle. Revs cleanly and can be driven.
The only codes are for misfires all on the one bank.
The left and right banks exhaust share common mufflers though in a design that would make an asymmetrical exhaust feel noticeable, and each pipe feels similar. It smells strongly of unburnt fuel consistent with the rich condition.

A well known LR independent in Adelaide have spent a few hours examining the car and are pretty convinced the timing chain has reached the point of no return. They feel strongly that the cats are ok given that there are no O2 codes with new sensors, and that either end of the cats look fine. This is contrary to a few members on this thread that have expressed strong concern for cat failure based on multiple experiences.

I can't quite rationalise the sudden failure that on resetting the faults immediately trips to fault again, unless a plastic chain guide has failed and the chain became suddenly loose. This would account for the noise also.

[DiscoJeffster]

I had a similar thing with a Porsche once. They use an interference fit for the cam wheels onto the camshaft. One slipped when I spun the car during an event (engine went backwards). It wasn’t running too bad but couldn’t pass the MOT for exhaust emissions. After trying everything they removed the engine and checked the cam timing and low and behold, it was out.

[101RRS]

A well known LR independent in Adelaide have spent a few hours examining the car and are pretty convinced the timing chain has reached the point of no return.

If you are happy with this independent then you have no option but to trust their judgement - however in my experience many repairers diagnose by replacement and charge the customer accordingly. So they will refund all costs if the chain is replaced and the problem continues?

If it is a chain then valve timing should be getting out of specs and the ECU cannot compensate spark to cope - won't the codes show this up? I dont know but is the sort of things I would be asking.

However, I appreciate that in many cases there are no options when stuck - I guess it is a judgement call.

Good luck with it.

[Globetrotter]

A timing chain rattle is very noticeable and engine would have running problems - not a smooth running engine. I would still be looking for electrical problems like an earth for that bank of ignition coils on the side giving the "misfire" symptoms. If no codes where showing up would you suspect anything wrong? Another thought is have you done a hard reset (battery leads off and linked together). As you say the exhaust smells"rich", have you removed a plug on the "faulty" side and see if its really sooty.

[Julian B]

If you are happy with this independent then you have no option but to trust their judgement - however in my experience many repairers diagnose by replacement and charge the customer accordingly. So they will refund all costs if the chain is replaced and the problem continues?

If it is a chain then valve timing should be getting out of specs and the ECU cannot compensate spark to cope - won't the codes show this up? I dont know but is the sort of things I would be asking.

Good luck with it.

The independent is not keen on the replace-parts-until-fault-resolves method, and their reputation is good. The issue with this Ford motor is that it is ultimately foreign to LR and although they agree that the absence of a timing mismatch code is odd, they have seen similar absence of codes in other cases for this motor.


A timing chain rattle is very noticeable and engine would have running problems - not a smooth running engine. I would still be looking for electrical problems like an earth for that bank of ignition coils on the side giving the "misfire" symptoms. If no codes where showing up would you suspect anything wrong? Another thought is have you done a hard reset (battery leads off and linked together). As you say the exhaust smells"rich", have you removed a plug on the "faulty" side and see if its really sooty.

The noise is subtle mostly when lifting off the gas in neutral. It runs roughish on idle but revs cleanly. I have done multiple hard resets to no avail. The plugs were replaced early (as were leads), all where in aged condition with a wide gap, but both banks were correct colour not burnt etc.


I am also not sure if there is a camshaft position sensor on both banks, but can find and confirm one on the left side which is not the bank with the error. See her (http://workshop-manuals.com/landrover/lr3/303-14a_electronic_engine_controls-_4.0l/description_and_operation/)e.
If the right hand bank were stretched alone (as might be seen with lubrication starvation/limitation to the chain on that side) then it could be late and rattly but the camshaft timing appears normal to the ECU as it reads off the other bank sensor alone. This would lead to poor running at low revs with a chain bouncing around, but applying throttle would tighten it up and it might run smoothly. The sudden change is hard to rationalise but a broken guide/tensioner could have caused overnight failure.

More exploration to do.

[DiscoJeffster]

The independent is not keen on the replace-parts-until-fault-resolves method, and their reputation is good. The issue with this Ford motor is that it is ultimately foreign to LR and although they agree that the absence of a timing mismatch code is odd, they have seen similar absence of codes in other cases for this motor.



The noise is subtle mostly when lifting off the gas in neutral. It runs roughish on idle but revs cleanly. I have done multiple hard resets to no avail. The plugs were replaced early (as were leads), all where in aged condition with a wide gap, but both banks were correct colour not burnt etc.


I am also not sure if there is a camshaft position sensor on both banks, but can find and confirm one on the left side which is not the bank with the error. See her (http://workshop-manuals.com/landrover/lr3/303-14a_electronic_engine_controls-_4.0l/description_and_operation/)e.
If the right hand bank were stretched alone (as might be seen with lubrication starvation/limitation to the chain on that side) then it could be late and rattly but the camshaft timing appears normal to the ECU as it reads off the other bank sensor alone. This would lead to poor running at low revs with a chain bouncing around, but applying throttle would tighten it up and it might run smoothly. The sudden change is hard to rationalise but a broken guide/tensioner could have caused overnight failure.

More exploration to do.

I’d sell it at this stage!

[Globetrotter]

Did you check fuse 17 in the battery fuse box. I would still pull a plug and check it. Have you pulled the connectors on the ECU and checked for corrosion

[Cconra14]

I have the EXACT same issue on my LR3 (yes I'm in USA but the 4.0 v6 versions here are almost non existent so I found this post from a Google search). My car is giving me misfires mostly on one cylinder at idle (although sometimes another cylinder on that bank), and car is negatively trimming that bank also. I have literally checked everything, compression, leak down test, fuel pressure test, replaced injectors, replaced plugs, checked for vacuum leaks. Even taken off valve covers and made sure timing is correct. I can not figure out the issue. Now I am thinking maybe O2 sensor on that bank, or maybe the engine control module? Unplugging O2 sensor does not seem to have any effect however. Any information on how you (hopefully) rectified your problem would be greatly appreciated, thank you.

[loanrangie]

I have the EXACT same issue on my LR3 (yes I'm in USA but the 4.0 v6 versions here are almost non existent so I found this post from a Google search). My car is giving me misfires mostly on one cylinder at idle (although sometimes another cylinder on that bank), and car is negatively trimming that bank also. I have literally checked everything, compression, leak down test, fuel pressure test, replaced injectors, replaced plugs, checked for vacuum leaks. Even taken off valve covers and made sure timing is correct. I can not figure out the issue. Now I am thinking maybe O2 sensor on that bank, or maybe the engine control module? Unplugging O2 sensor does not seem to have any effect however. Any information on how you (hopefully) rectified your problem would be greatly appreciated, thank you.

You need the DTC codes otherwise anything else is a guess.

[Cconra14]

You need the DTC codes otherwise anything else is a guess.

Codes are always the same no matter what I do, p0304 (sometimes p0306) p0300, p0316, and sometimes p0405, although thats and egr code and doesn't seem to always show up. Moving around coils, moving plugs, changing plugs, etc have all resulted in exact same performance. Oddly enough I drove the car this morning, fuel trim on the bank with the misfire was a little less negative, but still a misfire persisted. I am losing it over here trying to track this down.

[Globetrotter]

I had a similar problem with my 4.0 litre V6 which I eventually traced to a bad connection on the crankshaft position sensor (I think that is what is is called) which is situated at approx 11:00 position at rear of engine on the bell housing when viewed from inside the vehicle looking forward. Mine was a corroded connection, a clean up and all was good. It was not the easiest to get too. Any rattles from the engine like a timing chain noise as this can also cause a misfire.