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Discussion Starter #1
Car had slight misfire on start up and reduced engine performance message came up. As the car is a 2007 model, I replaced the auxiliary coolant pump, message is gone and car felt better.

However this morning the misfire seems worst than it was before although the "reduced engine performance" message is gone. The error codes are:
- p0302
- p0304
- p0306
-p0300

The above relates to multiple misfire, misfire on cylinders 2, 4 and 6 as well as at startup.

Also had (in the last year) the following done to resolve the issue:

- spark plugs - replaced a week ago
- ignition coils -moved around to check if misfire would go where "faulty" coil was moved; no joy as misfire was still at the same cylinder
- injectors - same as per ignition coils
- did compression test - according to both LR dealer and indie compression on all cylinders are ok

Had cats removed and engine remapped, although the misfire stems from before the afore-mentioned.

Help is appreciated as I'm at my wits end with this car
 

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I have similar problem on my2006SC. Sparks new, fuel filter new, swapped the ignition coils, clean the maf, oil new, filters new, battery new. I am changing the Range Rover step by step but I still have misfires. Engine is not warming up, I have low idle on the first start.
I added some injector cleaners. I clean the injectors 2 times, TB is clean as possible like mirror.
I am getting sometimes reduced engine performance on not working engine. I'm turning the key and just "click" reduced engine performance" after that.
If the engine is hot I haven't any problems.
Maybe the catalytic converters are bad.

I saw too much range rovers with this problem.
 

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Discussion Starter #3
Complete Exhaust, except headers, system is replaced, with no cats, so that should not be the problem. Although, (I forgot to include it in my post) one of the error codes also state that both system banks are too rich.

I'm still not convinced that it could be due to the removal of the cats because it did the same before the cats were removed
 

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Who did your remap?

Back on subject:

Under what conditions are the misfires most pronounced? Wide open, idle, only during warmup, etc.

You can't just remove the cats without compensating in the software. There is lambda correction based on post catalyst trims.
 

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Discussion Starter #5
Misfire is most pronounced at idle. However the misfire was there even before the cats were removed, so not convinced it is the cats, but will get O2 sensor extenders to see if that will help.

Must say car seems to pull much better than before we replaced the auxiliary coolant pump, especially from about 1900rpms
 

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Discussion Starter #6
Who did your remap?

Back on subject:

Under what conditions are the misfires most pronounced? Wide open, idle, only during warmup, etc.

You can't just remove the cats without compensating in the software. There is lambda correction based on post catalyst trims.
The tuner tried to compensate in the software for the cats that were removed
 

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Discussion Starter #7
Who did your remap?

Back on subject:

Under what conditions are the misfires most pronounced? Wide open, idle, only during warmup, etc.

You can't just remove the cats without compensating in the software. There is lambda correction based on post catalyst trims.
The tuner tried to compensate in the software for the cats that were removed
 

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Did you ever sort this?
I did.
I rebuild the engine
Cylinder compression was bad on 8th.
I replaced the exhaust valves did the head jop, replaced the timing chains

Now i have flashing check engine lights after 20k km
For 8 months we are searching the fault. Now i have misfires on 5th sometimes 2-4-6 it is not a mechanical issue
If you have misfires you have to check the compression first.
I think i have 1 or 2 bad wires On ignition system.
 

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Not sure what that means what was the psi?
Psi, kpa, kg, bar not important, lower is lower. If you have 100 psi on 6th and 80 on 8th you have to open the engine.
Never saw a range rover with piston rings problems, compression is lower due to burning valves on 8th or 7th mostly.

Im my situation everything starts with hesitstion on cold starts. Misfires on 8th then rich codes, after air leaks

We dont have miracles, if you have 4.2/4.4 engine and you have misfires first thing to do is checking the compression
If everything is normal, its a miracle
 

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but if you had 170 on one and 150 on the other you'd be ok wouldn't you as its thin the 25% tolerance? that's what I wondered what the good and bad were
 

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but if you had 170 on one and 150 on the other you'd be ok wouldn't you as its thin the 25% tolerance? that's what I wondered what the good and bad were
According to my experiences Tolerance at this engine is 10%
After that line begins cold start misfires

If anyone has hesitation or misfires on 7th and 8th cylinders has to check compression first.

Its a big and expensive job
I didnt belive at the beginning a 90k engine is gone, bought bunches of soare parts sensors then rebuild the engine
 

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