Discovery 1 V8 backfiring/misfiring under load.

seretical · Feb 17, 2024

Hi all,

My discovery 3.9 has a backfire/misfire under load. It only happens when going up hills when it kicks into high revs. It pops and bangs away out of the exhaust and it is very annoying, and the car starts shaking a bunch so I assume it’s missing.

It otherwise drives completely fine when not under load, starts fine, and is totally normal.

I’ve already replaced the plugs, leads, fuel filter and ignition coil but the problem persists. Not sure what to try next. The car has 340,000km on it.

Thanks everyone.

Stanleysteamer · Feb 17, 2024

Burnt valves?
Valve timing off?
Spark timing off?
Distributor advance problems? Or a combination of the above?
Or faintly possibly too much carbon in the head which heats up till it glows then fires the mixture early?

marjon · Feb 17, 2024

Why not finish the ignition side with a Distributor cap and rotor arm first. before going into other stuff.
Start with the cheap easy stuff.
With that amount of KLM it could be due a good refresh anyway, do you know its service history?

If I remember be careful of rotor arms as there are good 1s and useless 1s I cant remember which design is the best. But it has been mentioned on here before.

J

Stanleysteamer · Feb 17, 2024

marjon said:
Why not finish the ignition side with a Distributor cap and rotor arm first. before going into other stuff.
Start with the cheap easy stuff.
With that amount of KLM it could be due a good refresh anyway, do you know its service history?

If I remember be careful of rotor arms as there are good 1s and useless 1s I cant remember which design is the best. But it has been mentioned on here before.

J

I'd second that about rotor arms. Recently they have got to be totally cr@p. Lord knows why, how hard can it be to make decent ones?
Maybe better off with one from a scrapper.

discool · Feb 18, 2024

seretical said:
Hi all,

My discovery 3.9 has a backfire/misfire under load. It only happens when going up hills when it kicks into high revs. It pops and bangs away out of the exhaust and it is very annoying, and the car starts shaking a bunch so I assume it’s missing.

It otherwise drives completely fine when not under load, starts fine, and is totally normal.

I’ve already replaced the plugs, leads, fuel filter and ignition coil but the problem persists. Not sure what to try next. The car has 340,000km on it.

Thanks everyone.

The model year of your vehicle would handy.

Your EFI engine has a leased 7 important sensors that will cause a misfire if faulty, there’s a diagnostic facility that can be used which should give an indication of the issue which could just be a single part, or u can carry on with item replacements which you have been doing so far.

I see your vehicles mileage (211,266) is very high so is there may be some benefit in replacing everything

Discovery 1 V8 backfiring/misfiring under load.

seretical

New Member

Stanleysteamer

Well-Known Member

marjon

Well-Known Member

Stanleysteamer

Well-Known Member

discool

Well-Known Member

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