86 SE 2.8 - Misfire on 2 front cylinders (Page 4/5)
willyt AUG 20, 05:29 PM
Patrick, you might be on the right track here. Cylinder 1, when idle is held steady, appears to be pretty stable. The timing light appears almost always on, as in it is flashing so quickly it’s hard to tell it’s flashing. This is about 1500 rpm’s. There is an occasional point where the light doesn’t flash. Only for a brief second.


Cylinder 6 appears to be flashing at 1/2 or 1/4 speed. The flashes are easily distinguishable. Any thoughts? I can take a video if needed
willyt AUG 20, 05:34 PM
The other thing I just thought of was when I rev the motor, the mark moves, like spark is advancing. Shouldn’t it hold steady if the ALDL is jumped?
Patrick AUG 20, 05:46 PM

quote
Originally posted by willyt:

The other thing I just thought of was when I rev the motor, the mark moves, like spark is advancing. Shouldn’t it hold steady if the ALDL is jumped?



I'm not 100% sure.

Just to cover all bases, is your jumper connecting the Diagnostic and Ground terminals? Keep in mind that your ALDL port could be flipped over.

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

willyt AUG 20, 05:49 PM
Yes sir it is. Does the flashing at half speed mean anything to you? Wouldn’t this cause my misfire?
Patrick AUG 20, 05:54 PM

quote
Originally posted by willyt:

Cylinder 6 appears to be flashing at 1/2 or 1/4 speed. The flashes are easily distinguishable. Any thoughts?



That's what I was suspecting would be the case, but maybe an ignition expert could chime in now!

Do you know anyone local you can borrow known good ignition components from?
willyt AUG 20, 06:01 PM
Oh boy, if Patrick doesn’t know what to do then I’m really out of luck

I don’t know anyone I can borrow from, but I am miles ahead of where I was. I appreciate the help, I’ll do some research and see what I can find
Patrick AUG 20, 06:07 PM

quote
Originally posted by willyt:

Oh boy, if Patrick doesn’t know what to do then I’m really out of luck



Oh man, I'm no expert with these cars. I know a little bit about a lot of things. There are plenty of members here who know a heckuva lot more than I do on specific issues.
PhatMax AUG 20, 06:59 PM
The magnet is just above the pickup coil. It’s sandwiched between two plates. If it’s cracked it will cause a miss. I know for a fact as I had a friend with an 86 that ran like crap…they changed, exhaust….thought it was a clogged cat, cap, rotor, wires, plugs.a bunch of sensors…..finally on a whim bought a new dist….and it ran like new. The one that Cardone now has is updated and should alleviate the problem.
As the magnet spins it will cause a break in the voltage present in the pickup coil…..that is what causes the ICM to fire. If the magnet is all cracked you will have all kinds of false triggers …or no trigger at all.
willyt AUG 20, 07:01 PM
Okay I played around with the timing light a little more and it looks like when I wiggle the pickup around it changes the frequency at which it flashes. I don’t think the misfiring cylinders are actually doing anything different.

Got a code 34, working on that now.
willyt AUG 20, 09:19 PM
After a few more tests, and a short drive, I am pretty close to losing my mind.

The only thing that I can find wrong with the car is that the fuel pressure drops over time. Over the course of 10 minutes, it drops from 43, down to 30.

If an injector was leaking, would it be obvious with the above test?

Is it possible that any other cause of this would make two specific cylinders misfire?