Misfire might be related to O2 sensors, maybe? Not sure how the engine management on a D2 deals with them but on the old 14CUX hotwire system the ecu ignores the O2 sensors until the engine is warm so can run fine when cold and at WOT but be a nightmare in between with misfiring and rough idling. If an O2 sensor is failing you might get intermittent issues that will get progressively worse until the ecu can't deal with the swings in fuelling because of a faulty O2 signal then it should, in theory pop the engine management light on and drop in to limp mode.
Machine gun noise often is exhaust manifold gasket.

HTH
 
Just replaced the plugs and there fine came in and out perfectly. I wondered about head gasket, and had them go on other cars, from my experience once they go the go not intermittently, same with manifolds / gasket . Did a 50 mile journey today and she ran like a dream for about 20 miles . Random!
My mk2 4ltr engine management light comes on with loss of power and computer shows’misfire on cylinders 6&8’
Any ideas?!
 
I've had very similar noises and symptoms from my 4.6.

Starts and runs fine, then misfire under load. Sometimes it drives well for a while then goes through a period of rough running. Chuffing sound reflected from nearby surfaces etc.

I had several faults (it's still not totally sorted) but the chuffing was deffo from a leaky exhaust manifold gasket.

During the course of my investigations I found I have low compression on most of the cylinders and I now think that's the cause of the misfireing. I've replaced the coil pack, plugs, cats, and all the exhaust gaskets associated. I think I'm now looking at a replacement engine, or a lot of rebuilding of my current one!

I'm going to try some of Restore Engine Restorer as a temporary fix to try and buy myself some time, until I can decide what to do about the engine.....
 
My mk2 4ltr engine management light comes on with loss of power and computer shows’misfire on cylinders 6&8’
Any ideas?!
It's possibly not the coil pack because cylinder 1&5 would misfire too.
Start small and check both HT wire conditions and check spark plug gaps on 6&8. When were the plugs last changed?
 
It's possibly not the coil pack because cylinder 1&5 would misfire too.
Start small and check both HT wire conditions and check spark plug gaps on 6&8. When were the plugs last changed?
New Plugs and Leads. I think it’s the Head Gasket. Can anyone recommend a good Head Gasket set to buy.
Thanks
 
I've had very similar noises and symptoms from my 4.6.

Starts and runs fine, then misfire under load. Sometimes it drives well for a while then goes through a period of rough running. Chuffing sound reflected from nearby surfaces etc.

I had several faults (it's still not totally sorted) but the chuffing was deffo from a leaky exhaust manifold gasket.

During the course of my investigations I found I have low compression on most of the cylinders and I now think that's the cause of the misfireing. I've replaced the coil pack, plugs, cats, and all the exhaust gaskets associated. I think I'm now looking at a replacement engine, or a lot of rebuilding of my current one!

I'm going to try some of Restore Engine Restorer as a temporary fix to try and buy myself some time, until I can decide what to do about the engine.....
Think it’s actually head gasket so looking to get this done.
Looking for recommendations as to Head Gasket Set to buy.
Thanks
 
When I did mine I went to Turner engineering. All top quality, and excellent service.

They're also still open! Google them, they're Rover V8 rebuilders.
 

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