Fj60 misfire (1 Viewer)

[Spears41]

Good evening, all.

I’ve been making some real progress on my 1984 FJ60 with original 2F. I’ve now driven it 20k miles since I got it 3+ years ago (fixing and learning as I go), but I’m hitting a snag and need some guidance.

Cylinder 3 is misfiring during warmup consistently. I’ll start it up in the garage (climate controlled 70 degrees) and the idle is really rough. I isolated it to cylinder 3 by pulling plug wires until it didn’t change the engine speed/noise. Next I pulled the #3 plug, which looks ok and similar to others. Compression was 110. While I was at it, I went ahead and checked compression across all cylinders: 110-120. Vac during warmup oscillates between 117-119, ticking down during the misfire for #3. After 5-10 minutes it purrs and vac stays at 19 solid. Cylinder 3 no longer misfires.

I’ve considered a blown head gasket (had that replaced a little over a year ago) with coolant leaking into the cylinder. Factors against this are the lack of overheating, and I don’t see oil in the coolant or coolant in the oil.

I figured a sticking valve would give me a super low compression number. I would expect a worn out cylinder would give me a little lower number, or at least wouldn’t improve after warmup. I’d love to get some input from the experts here on possibilities/next steps.

Thank you in advance.

 

[HemiAlex]

Have you adjusted the valves yet?

 

[Spears41]

Have you adjusted the valves yet?

No I haven’t. They were adjusted by the local cruiser mechanic about a year and a half ago when the head was rebuilt, but I’ve never touched them myself

 

[Spears41]

I suppose I should add, I do see some grey/white smoke from the exhaust for the first few minutes with startup. I’ve never had to add oil but didn’t want to leave that bit out. Seems that the misfire goes away around the same time the smoke does

 

[OSS]

If pulling a spark plug wire makes no difference- the misfire is ignition based — and the problem is downstream of the coil.
Try replacing the distributor cap and rotor and replace spark plug wire #3 to rule it out - and of course spark plug #3.
See if that does something.

 

[Spears41]

If pulling a spark plug wire makes no difference- the misfire is ignition based — and the problem is downstream of the coil.
Try replacing the distributor cap and rotor and replace spark plug wire #3 to rule it out - and of course spark plug #3.
See if that does something.

@OSS you’ve bailed me out more than once. Thanks for the continued gifts of knowledge. I will report back.

 

[Seth S]

I suppose I should add, I do see some grey/white smoke from the exhaust for the first few minutes with startup. I’ve never had to add oil but didn’t want to leave that bit out. Seems that the misfire goes away around the same time the smoke does

This is likely just condensation in the exhaust...normal. Its when the white clouds dont go away or create a cumulus cloud behind you that its a worry

 

[Spears41]

Thanks @OSS. Problem fixed. Cracked ceramic around the spark plug.