Disco 2 Misfire (I think!) / Overboost

Evening All

I've never driven a Disco that has suffered with a misfire, so I'm struggling to figure out if that's the issue with mine. All revs below about 2k, the engine runs fine, however, when I try to accelerate up a hill, putting the engine under load and with the revs going over 2k, the engine feels as if it's going to shake itself to bits. Its not the drivetrain (I think), because on the flat, the engine will rev up to 3k smoothly (for a diesel).

I've already fitted a new genuine MAF, FPR and the engine has been de-EGR'd. I've also checked the red connector for oil, and cleaned out what I did find. I've also fitted a new wastegate modulator. Unfortunately, I don't have access to a Nanocom or similar, so I can't find out what (if any) codes are being generated by the engine management.

I do need a new DM Flywheel (and all the other clutchy bits), but I'm now considering buying a Nanocom with the money, and then do the flywheel and clutch later..... Could it be the DM Flywheel that's causing the engine vibrations?

Cheers

You say you cleaned out red plug on injector harness this my suggest you need a new harness fitting, you symptoms certainly could point to it

Sorry, I forgot to include in my first post that I've replaced the injector harness already after I found the oil in the red plug.

ok need a rethink then

Does it smoke when misfiring?
Mark

No, it doesn't give off any smoke at all when it's shaking.

This may be of some help, but I could be miles off. When I replaced my injector loom, I got a misfire, although it was constant. It was the connecting plug from the new injector loom, where it connects by the rocker cover. I found if I wiggled it, the misfire stopped. A good clean with switch cleaner and allowing it to dry for a couple hours before reconnecting sorted the problem.

As you had this problem before and after changing the loom, it probably isn't this, but may be worth a look. Sorry I can't be of any further help. Good luck!

I had the same problem. It was the fuel pump and fuel regulator. The misfire was caused by low fuel pressure at the cylinder head. I would try the wastegate 1st and in your shoes it would be the next thing I checked as it is effectively free.

I've found with mine that it always sounds a bit like a misfire, it's a trait of the 5 cylinder engine. The injector seals also made a difference.

Haystacks said:

This may be of some help, but I could be miles off. When I replaced my injector loom, I got a misfire, although it was constant. It was the connecting plug from the new injector loom, where it connects by the rocker cover. I found if I wiggled it, the misfire stopped. A good clean with switch cleaner and allowing it to dry for a couple hours before reconnecting sorted the problem.

As you had this problem before and after changing the loom, it probably isn't this, but may be worth a look. Sorry I can't be of any further help. Good luck!

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I know where you mean, I'll check it later.

gazman said:

I had the same problem. It was the fuel pump and fuel regulator. The misfire was caused by low fuel pressure at the cylinder head. I would try the wastegate 1st and in your shoes it would be the next thing I checked as it is effectively free.

I've found with mine that it always sounds a bit like a misfire, it's a trait of the 5 cylinder engine. The injector seals also made a difference.

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I'll check the wastegate, thanks. I've already replaced the FPR, but it could be the fuel pump itself.

I really need to get some diagnostic equipment on it so I can stop replacing parts in the hope that it might fix the issue..

Little update on this issue. After much reading of many threads relating to similar issues, I checked the operation of the wastegate, and it was fine and moved smoothly, albeit, very stiffly. Took the car for a drive, no change. It still suffered from the shuddering at high revs under load, so I decided to try the wastegate regulator bypass mod, and all of a sudden my Disco drives like it's got a new engine!! So I have to assume that the shuddering / misfire I was feeling was actually overboosting, causing the ecu to cut the fuel. This means the new wastegate regulator I recently fitted is either knackered, or there's another issue related to this that's causing the issue.

So, the question is, can I leave the regulator bypassed without causing any issues? I know this is effectively how the Defender engine is plumbed, but I'm sure the Land Rover fitted this regulator for a good reason

Anyone?

That wastegate modulator is there with a good reason even though the car runs without it quite well it would run much better with a well working one, check fuse F2 engine bay fusebox to rule out the modulator's feed

sierrafery said:

That wastegate modulator is there with a good reason even though the car runs without it quite well it would run much better with a well working one, check fuse F2 engine bay fusebox to rule out the modulator's feed

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Just checked, the F2 fuse is good. I'll order another new wastegate modulator.

I would be taking the in tank pump out and giving it a check over , the main filter on the pump could be blocked causing low fuel pressure, not just the bottom strainer.

I had exactly the same trouble a month ago, went down the same checking route you have and the wastgate bypass, in the end it was the in tank fuel pump that was at fault, not delivering enough pressure

Joemac434 said:

I had exactly the same trouble a month ago, went down the same checking route you have and the wastgate bypass, in the end it was the in tank fuel pump that was at fault, not delivering enough pressure

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Thanks, I'll get it checked. I'm in the process of checking the sofa for some pennies to buy a Nanocom at the moment, so a new FP may have to wait.

I've refitted the wastegate modulator in the meantime so I don't cause any more problems

Regarding the FP, can I get away with an aftermarket unit, or is this another case of genuine only?

VDO is the best but if you are short of money a cheaper but still not sh*t like the very cheap pumps is this one http://www.buycarparts.co.uk/mapco/7644317 , those cheap around 70 quid pumps are noisy and unreliable

Thanks Sierrafery, although money is tight at the moment, I'll buy the VDO unit.

Just wanted to close this thread with a resolution, well for me anyway.

My rough running was due to a faulty fuel pump