coil packs?

[Curmudgeon54]

Dumb question of the day: When FJ coils go "bad", is it normally a sudden event (i.e., the bike simply stops running), or is it a gradual deterioration? My recently acquired '85 FJ1100 -- which sat unused for many years -- will sometimes run okay, but other times will be almost undriveable because of what feels like severe ignition miss. It has new, properly gapped NGK plugs, and I've tried three different ignitor boxes with no change.

Dumb question number two: Is an FJ1200's electronic ignition box a worthwhile swap? Thanks for any input...

[fj1289]

Not answer for your original question...but something else to look at.

New plugs were a very good step.  Also make sure the battery is in good condition.   I've had a battery with a bad cell (twice) cause similar issues.   It would turn the starter motor over just fine and start easily, but would have an intermittent miss or rough running.   Replacing the battery cleared it up. 

[red]

When FJ coils go "bad", is it normally a sudden event (i.e., the bike simply stops running), or is it a gradual deterioration? My recently acquired '85 FJ1100 -- which sat unused for many years -- will sometimes run okay, but other times will be almost undriveable because of what feels like severe ignition miss. It has new, properly gapped NGK plugs, and I've tried three different ignitor boxes with no change.

Curmudgeon,

Coil packs (in any vehicle) can go bad by cracking physically, allowing moisture to get in.  If things get better after a long hot ride, the problem may be cracks (and moisture) rather than an electrical failure as such.  Were the "bad" days when high humidity (or condensation) was present?  

So yes, coils can deteriorate over time, but one day they will just die.  An electrical test of the failing coil may not reveal the problem, if cracks and moisture are to blame.
.

[Curmudgeon54]

Thanks, gents. The battery is new and freshly charged, so I can scratch that off the list. And the ignition breakdown usually seems to get worse as the ride goes on -- in warm or cold weather --  so I don't think moisture is the culprit.

[Pat Conlon]

First off...I am assuming you have followed the service manual and properly bench tested your coils and they passed. Intermittent electrical problems are a bitch. They bench test fine only to act up 2 hours into a ride.

When it runs poorly, can you isolate which cylinder(s) are affected?
As you sit on the bike, The left coil fires cylinders #1 & 4 and the right coil fires #2 & 3.
Because our FJ's use a wasted spark ignition sequence, if you have a bad coil it will affect 2 cylinders (1/4 or 2/3)  not just one cylinder.
If you have 2 cylinders dropping out (1/4 or 2/3) try swapping coils, move the left coil over to the right side and vice versa, and see if the problem follows over to the new cylinders.
If you have just 1 cylinder dropping out, try swapping plug leads (from the same coil) and see if the problem follows the swap or stays on the same cylinder. e.g. if #1 cylinder is misfiring, swap the plug wire with #4 (same coil) and see if the problem moves. If the problem moves then look at your plug wires or resistor cap. If the problem stays on #1, then look at your plug.
I have bought a set of new NGK plugs only upon close inspection to find one with a hairline cracked insulator.

I find the oem FJ coils and stainless steel core plug wires to be very durable.

I had a ignition misfire problem years ago and my friend Mark Olsen told me where to check...it was the run/stop switch on my throttle assembly. Though the years and miles my switch needed a cleaning. This on/off switch controls the circuit which powers the ignition box and it was intermittently dropping power to the box.
Yea....Intermittent electrical problems are a bitch...
I found this out after running a temporary 12v power wire from my battery's positive terminal over to the ignition box and after a long ride, finding that the problem went away. I then followed the ignition box power circuit backwards.
I think I still owe Mark a WCR breakfast for his help...

[Curmudgeon54]

Thanks, Pat, for the suggestions. I'll follow up on them over the coming days. Trouble is, winter is upon us here in Canada, so may have very few opportunities to test ride...