2004 SE Disco II,, wife put reg gas in it a few times and today it started misfiring on cyl 3, she said she smelt some burning as well. I had her top it off with correct fuel and some fuel injector cleaner. Working on it now I dont notice any burning, (cat maybe?) looks fine, Starts fine, idles fine , misfire happens around 2500 rpm and drives sluggish. No coolant leaks, oil looks good,checked spark plug and wire, Last tune up I used Bosch iridium plugs.

Bought used with 90,000, plug wires not original what else should i be looking at? thanks

 

When I got a misfire it turned out to be coil pack. If you have the code try searching this forum for the code, should find lots of hits

 

@ weepit , thanks for the reply, I was thinking in the back of my head it might be the coil pack, Im getting codes for cyl 3 misfire and i did just get a cyl 6 misfire very briefly but im clearing them as i go and the cyl 3 seems to be the prevalent code here, when your truck started misfiring what codes/other symptoms did you have? is there a good write up on checking the coil / voltage output at plug wires?? It sure does look like a bisnatch to take the coil pack out.

 

I would check the #3 plug wire very carefully for cracks or splits. If they are the original 7mm wires then it is time for an upgrade to the 8mm. The insulation inside the boot will become hard over time and it is easy to break and poke a hole in the boot. You can try looking at the #3 wire in the dark while it's running and see it you see any spark coming from the boot or wire.

Another possibility is a clogged fuel injector.

 

starts idles fine then p0303 @ 1929RPM is the pattern

 

wires are not original, previous owner replaced them during a tune up and they all look good though, when it gets dark tonight im going to check for any signs of arcing. tried different spark plug, still no good will try a swapping a wire here in a minute, got to find a good one laying around here somewhere. Can anyone point me in the direction of using a multimeter to check the wires, wanna make sure Im doing it right. Also the burning smell i mentioned earlier i believe may have been a clump of electrical tape i just discovered on the exhaust manifold lol, and apparently my no. 2 spark plug boot was loose.

 

Put the meter on Ohms then put a lead on each end of the plug wire.

As long as you dont get "OL" (open loop) or a ridiculously high resistance it should be good.

 

standard procedure, new plug, new wire, compression test then coil pack. just because a plug or wire is new doesn't mean it can not fail.

 

"I" would swap the plug and wire and see if the misfire follows

 

I double checked the wire on the cyl 3 and it is indeed no good, Just got some brand new plug wires, hopefully this does the trick.