S8 lumpy Tickover

[lerd]

My friends s 8 d2
He uses it frequently
It's always been good running but he didn't use it for two weeks and when he started it up the cat light was on the dash, and the engine is ticking over lumpy and when you Rev it it seems to mis
Looked in the owners manual and it said cat light will be on when cat gets too hot
Trouble is the light is on when started from cold
Any ideas it's doing his head in
Cheers

[PositronicRay]

[sdkrc]

Sounds like a misfire.
The 4.2L engines from that period are prone to misfires.

[Adrian E]

Mine used to be left for weeks in winter and no amateur dramatics when used - anything here is guesswork - it needs plugging into VCDS to find out the cause of the MIL on. Had mine for 6 years and never had a misfire - other newer V8s suffered coilpack faults, but D2 uses an older design

[daemon]

sdkrc said:

Sounds like a misfire.
The 4.2L engines from that period are prone to misfires.

Surely a "misfire" is a symptom of a problem, not the problem itself?

[Rich_W]

daemon said:

sdkrc said:

Sounds like a misfire.
The 4.2L engines from that period are prone to misfires.

Surely a "misfire" is a symptom of a problem, not the problem itself?

OP. What does the fault code reader say? Easy enough to check. Lets say misfire on number 1.

Swap coils from 1 and 2.
AND
Swap plugs 1 and 3.
Clear fault codes and run again.
See if misfire migrated from 1 to 2 or 3.
If it stayed on 1. Run compression check. If ok. Replace injector first
If went to 2 then new coil required
If it went to 3 then new plugs.