Discovery 2 Misfire

Hoping someone can give some clues to solving an ongoing problem with my Disco 2001 TD5. I have searched the threads on this and other sites but none give a conclusive answer.

For a while now I have had what appears to be a misfire on perhaps one cylinder that comes in at 2100 revs. This stays until the revs reach about 2600 revs before appearing to smooth out and the engine fires on all cylinders. During this band of revs the engine takes on a lumpy rumbling tone and vibrations run through the bodywork. The motor has 116,00 miles on it and is the 10p engine.

There are no faults showing on Nanocom. (other than EGR) So far I have changed again the injector loom, the EGR was removed/blanked when I first got the vehicle, all oils are fresh as are all filters, I have rewired the engine loom directly from the ECU to the injector loom plug under the cam cover, recently removed and cleaned all the injectors, fitted new injector copper washers and O rings, new battery fitted. Checked the auto gearbox flex plate for cracks but all seems ok, released the exhaust rubber hangers and moved it about but with no change, fitted new engine mounts, no oil in loom or ECU, tried another ECU, checked the throttle track/voltages with Nanocom all seems well, checked the front crankshaft harmonic balancer/damper (slight play in it but only a tiny amount). When I was rewiring the engine/injector loom I disconnected one injector at a time and all seemed to have the same effect on the engine and could not see or hear any cylinder having a distinct effect on the misfire. Running out of ideas that don’t involve lots of expense.

Not yet done a cylinder pressure test owing to the difficulty of the job and having the right kit. Also cannot test No 5 pot as has no glow plug. Cylinder balance though shows up ok on Nanocom.

The engine does this when driving and also stationary in Park and Neutral, no smoke or soot from exhaust, same when engine is hot or cold. Is no worse when under load and overall does not seem to lack power.

Any sensible ideas anyone?

Can you post a file showing the engine data when it is running, taken from the nanocom, as you say it is happening when vehicle is stationary can be done then.

Cheers

neilly said:

Can you post a file showing the engine data when it is running, taken from the nanocom, as you say it is happening when vehicle is stationary can be don
Cheers

Click to expand...

THanks

Ok. Will get to that this afternoon and post it.

Hi, the lack of fault codes and overall good live data can be a sign of some fuel supply issue which affects the engine between those revs, first move should be to put a new good brand fuel filter and check the strainer which is in the head under the FPR ... btw the FPR is in good shape, no leak at all?

Hi Sierrafery
I shall give the fuel filter a change as I have a new one. Though the last one is only a couple of thousand miles used. I'd thought about the FPR, would a pressure test on it show faults? No leaks from it by the way.

I suspect some fuel restriction which is not noticeable at low revs while the engine doesnt need so much fuel up to 2100rpm and which is overriden by the higher reguest above 2600....it's something to be ruled out, that strainer beneath the FPR is a good start, though if you get to it prepare a new FPR gasket

Hi Neilly,
Here are the files. Readings at idle speed, approx. 2000rpm and approx. 2600rpm.
I see that on the cylinder reading No5 pot gives wide readings at higher revs but am led to believe these readings are only relevant at idle speed?
Steve

Hi again Neilly
Seems the Exel files didn't load as the site doesn't like the excel or CSC extensions

HI @smac02

Have you tried saving as a PDF file?
like this

Cheers

Was to be my next plan but had to go out. Here we go then

sierrafery said:

I suspect some fuel restriction which is not noticeable at low revs while the engine doesnt need so much fuel up to 2100rpm and which is overriden by the higher reguest above 2600....it's something to be ruled out, that strainer beneath the FPR is a good start, though if you get to it prepare a new FPR gasket

Click to expand...

Hi again
Ive been looking at the FPR repair kits. Are they any good. Ive read some poor reviews of them. Are there any you could recommend or would a complete new unit be the best option.
Steve

No need for such thing as long as it's not leaking IMO.... though if you'll need one a new genuine unit is the best all the way cos that means another at least 10 years of no worries in that area, any other option is a lottery, which means you can win too

I've now changed the fuel filter, no change in misfire. Have also changed the FPR and cleaned the fuel filter in the head, no change in misfire.
I've a bit more time studying the misfire too. The misfire comes in at 1800 revs and actually remains throughout the rest of the rev range.
Also, topped up the water tank ank and have some very small bubbles that are not constant. (My previous disco 2 did the same with no ill effects) I have no signs of overheating or water loss even when I've driven fully laden and towing 1500kg of caravan.
I'm now guessing a failed head gasket. Any further thoughts anyone.

Not sure if this will help , But as the symptoms have changed from the OP.

but did you check the wastegate actuator rod movement?

Have you tried the wastegate modulator bypass?

Does the expansion tank require topping up often?

Cheers

Also, Have you checked the fuel pressure?

Cheers

Don't know if it will help but I had exactly the same symptoms as you describe. Same rev range, driving or stationary, no loss of power. I was thinking misfire or maybe engine or gearbox mount but then checked my viscous fan. There was a fair bit of play in the bearing (the fan itself not the pulley) so I took it off. Immediately quieter and vibration virtually gone. As an aside, I wasn't 100% sure it was completely gone but thought I was probably being paranoid and hypersensitive to any noises or vibration. Anyway, i had my MOT on Thursday and it failed on emissions - 8.4 so very high. I changed my thermostat (a job I've been putting off for ages) air filter and stuck in a bottle of Cataclean. (Recommended by the garage) Passed today at 0.14! Point being, if I did have a misfire which was causing the high emissions, the Cataclean seemed to sort it out. Either way, try running without the fan first to see if it makes a difference.

neilly said:

Not sure if this will help , But as the symptoms have changed from the OP.

but did you check the wastegate actuator rod movement?

Have you tried the wastegate modulator bypass?

Does the expansion tank require topping up often?

Cheers

Click to expand...

Hi Neilly
The water needs about half a cupful every month. As I mentioned no signs whatsoever of overheating just these very small bubbles which puts some doubt in my mind.
I was wondering if maybe the head gasket has split between two cylinders?
Not tried the modulator bypass yet, meant to but forgot. The wastegate is free to move. Takes some moving against the spring but it does move. I had a look at my readouts but not sue what I'm looking for on the wastgate readout.
I'm going to get the engine hot tomorrow and check the header tank again. Also try the modulator test, I've got some tubing somewhere

smac02 said:

Hi Neilly
The water needs about half a cupful every month. As I mentioned no signs whatsoever of overheating just these very small bubbles which puts some doubt in my mind.
I was wondering if maybe the head gasket has split between two cylinders?
Not tried the modulator bypass yet, meant to but forgot. The wastegate is free to move. Takes some moving against the spring but it does move. I had a look at my readouts but not sue what I'm looking for on the wastgate readout.
I'm going to get the engine hot tomorrow and check the header tank again. Also try the modulator test, I've got some tubing somewhere

Click to expand...

Forgot to add. Not checked the fuel pump yet. I had it out once and it looked like the original. Is that what you were getting with the fuel pressure. Rather than spend loads on various bits of testing kit (though I like buying tools) I may drop the thing into my local Landy expert for a diagnosis, though I have little faith in my workshops.