D2, Brief Ignition Coil/Misfire Question

[bjamin]

My friend recently rescued a 2000 D2 from a unloving home. The spark plugs and wires were absolutely shot, and the engine was misfiring on multiple cylinders. After replacing all plugs and wires the misfires stopped and the engine ran great.

However, now a little over two weeks later the loss of power is back, and misfires recorded on cylinders 3, 4, and 5. My question is this:

Would the shitty wires and plugs have put enough extra stress on the coil packs to make them throw in the towel? Per a DWeb thread, we measured resistance between designated pairs of wires (plug ends) and found the values to be same range (22 to 26 kOhms).

Should we replace the coil packs? If not, does that only leave an ECU issue? Also, if we pull the coil packs, will testing primary and secondary coil resistance determine if they still function properly?

Thanks!

Note:
In addition to misfire codes, the scan tool also shows P1884 which after a lot of searching seems to be an unknown/multiple definition code.

 

[JRL]

Also to note: the plugs are stock replacement Champions and the plug wires are STI. Thanks for the help!

-John (The Rescuer)

 

[BigD]

I had a coil pack failure which I attribute to incorrect plugs being fitted. When I serviced my vehicle for the first time I noticed that the previous owner had the correct plugs fitted to the right bank (Champion EOS platinum) however on the left bank there were two NGK and two normal champion plugs fitted. Shortly after I installed 8 new EOS plugs I strted getting the misfire on no 7.

Bad plug wires will definately make a coil go bad. If the spark has nowhere to go it usually sparks through the insulation of the coil wires inside the coil. gradually breaking the coil down.

 

[ptschram]

Magnecor and cheapie Champions.

 

[Kacers]

Test 3,4,5 wires with in-line test light to see if you are getting good spark to the plug. If not, move your way backwards to find the issue. I would not rely on any multimeter readings on the wires as those are HT leads and operate differently from 'normal' voltage wiring. I personally have never found an easy and accurate way to test them but thats just me.

The coil packs on my '04 are arranged as follows - left to right is from PS to DS as you look at engine from the front bumper - and going top to bottom. I assume your Disco is the same. There are two coil packs. 8/5/2/3 are served by one coil pack on the PS. 6/1/4/7 are served by another on the DS.

8 5 6 1
2 3 4 7

Misfire on 3,4,5 would be odd as it would mean both coil packs are bad. Also, the plugs/wires use the wasted spark principle so if the coil was bad, it would show in misfire on the both cylinders where the spark is shared. Again, since you have 3,4,5 misfires and these are not mated for ignition than this tends to suggest not a coil issue.

So, after all this, I would say replace wires with magnecore. Or swap some wires and see if the misfire moves to where you moved the suspect wire.

AndrewT

 

[hywy61]

did you remove the intake to replace the wires ?

 

[ptschram]

I would not rely on any multimeter readings on the wires as those are HT leads and operate differently from 'normal' voltage wiring.


AndrewT

This test merely shows a continuous circuit through the secondary of the coil pack and is very handy for ruling out the coil pack.

 

[BigD]

did you remove the intake to replace the wires ?

Initially I replaced the plug wires without removing the manifold. Very fiddly job. Have the scars on my hands to prove it.:ack: It can be done.

Removing the manifold is really not that hard. If you follow the instructions on the Rave cd it takes about 20 min.

If you want to remove the coils you have to remove the manifold on a Disco II, don't know about DiscoI.

 

[Kacers]

This test merely shows a continuous circuit through the secondary of the coil pack and is very handy for ruling out the coil pack.

Thx - Good to know. Learn something new every day.

AndrewT

 

[JRL]

I replaced the 2 coil packs last night (fun...) and it runs like a champ! Now I've just gotta let it drive cycle and hope nothing comes up. =)