86 SE 2.8 - Misfire on 2 front cylinders (Page 3/5)
Patrick AUG 20, 02:41 PM

quote
Originally posted by willyt:

I checked timing and it looked good. Right at 10 degrees.



With ALDL jumper in place?
willyt AUG 20, 02:42 PM
Yes sir
PhatMax AUG 20, 04:34 PM
Man, at this point I’d look at the dist.. specifically the magnet, could be giving false or erratic trigger.
willyt AUG 20, 04:41 PM
I just replaced the cap and rotor, what do you mean by the magnet? Any good way to check?
Patrick AUG 20, 04:46 PM

Just curious... but if you connect your timing light to the spark plug leads of cylinders that appear to be firing properly, and to the spark plug leads of cylinders that don't appear to be firing properly... do you see a steady flash in both situations... or do you see some irregularity in flashes with the "bad" cylinders?
willyt AUG 20, 04:50 PM
I definitely saw irregularity in the cylinders that are firing correctly, let me check one that isn’t. Give me about 5 minutes here.
Patrick AUG 20, 04:54 PM

quote
Originally posted by willyt:

I definitely saw irregularity in the cylinders that are firing correctly...



That's weird. I would've thought those cylinders should've been rock steady.

[This message has been edited by Patrick (edited 08-20-2022).]

willyt AUG 20, 05:00 PM
Patrick, it’s hard to tell but it seems like there are more irregularities with cylinder 1. When I tile cylinder 1, it bounces around a bit but it averages around 10 degrees.

When I time cylinder 6(one of the bad ones) I see two timing marks, but they appear more steady. One around 0 one around 10.

Any thoughts?
Patrick AUG 20, 05:10 PM
I wasn't even concerned with the timing, I was more interested in simply how regular and/or steady the flash pulses were.

I don't understand why the flash pulses are all over the place... unless it's due to the idle speed fluctuating. I wonder if the flash pulses would be steadier on the "good" cylinders if you held the throttle open at say 2000 RPM. If so, then repeat with the "bad" cylinders and see if there's any difference. I'm trying to determine if you can "see" when the suspect cylinders aren't firing.

[EDIT] I was going with the "all or nothing" theory in regards to spark in the "bad" cylinders... but yes, I suppose it could also be a situation where for whatever reason the spark could still be occurring in all of the cylinders, albeit with very erratic timing... as PhatMax was suggesting.

[This message has been edited by Patrick (edited 08-20-2022).]

willyt AUG 20, 05:22 PM
Interesting, it probably is due to idle speed. Give me 5 I’ll see what I see