Intermittent Spark problem on '86 truck with 22R

Hi:

I think that I'm having an intermittent spark problem with my 1986 Toyota pickup (4x2, 22R). The engine sounds and feels like it is running on three cylinders under load. It doesn't happen all the time (but very frequently) and only after the truck is warmed up for a little bit. I was able to get the engine to stumble when it was parked in the garage one day by blipping the throttle quickly from idle. I hooked up my timing light to one of the spark plug wires and noticed that the light "stumbled" as the engine stumbled when I blipped the throttle. I then hooked the timing light up to the main ignition wire that runs from the coil to the distributor and noticed that the light stumbled when the engine stumbled.

The spark plugs have only about a couple of thousand miles on them and look fine and are gapped correctly. Although the spark plug wires for

12 years old they have no cracks or other visible damage and test well within specs. I performed the factory manual recommended tests for the coil and the distributor, and everything tested within specs. Since I didn't find a way to directly test the ingiter, I bit the bullet and replaced it with a new Toyota igniter (ouch!). Unfortunately, that didn't solve the problem.

I didn't test the ECU which is located behind a kick panel on the passenger side. I'm not even sure what the ECU does anyway on a carbureted truck.

Since the timing light "stumbled" when I connected it to the ignition wire coming from the coil to the distributor, does that mean that there is a problem on the coil/igniter "side" rather than the distributor/individual spark plug "side" of the ignition? I could just replace the coil and see what happens. Although it's cheap when compared to the cost of the igniter, it's not THAT cheap.

Any thoughts as to what the problem might be? Any help would be greatly appreciated. Thanks.

-- -- Mike

Reply to
Mike
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Geez louise, man just spend $50 and get some new cables. I replace mine every few years along with the rotor and cap. They do degrade over time.

Depends on how much emissions control you have on your truck.

Check your distributor, to make sure it is working consistently.

Reply to
Ernie Leimkuhler

Thanks, Ernie, for replying. Can you elaborate how my plug wires may have "degraded" over time despite having resistance readings in the 8K ohm range (well within specs), being very supple, having no cracks, and having terminals in good shape? I tend to be of the mind that just because things are "old", doesn't mean they're broke. It's not like I am merely being cheap about this issue. Recall that did replace the igniter ($$$$$$$$$). Changing wires every few years as preventative maintenance seems a tad excessive, compared with my experience of owning and properly maintaining several high mileage vehicles (200-300k miles), with plug wire sets that have functioned well for many, many years.

Whatever came stock on a Federal 22r...

Vacuum advance works fine, air gap is good, plates and shaft seem good. I wiggled the pick-up coil wires as I tested the resistance, which was fine.

I am leaning toward the coil at this point. Is it common for coils to have intermittent problems? The ones that I have had that failed, have failed completely. Thanks.

Mike

Reply to
Mike

The high voltage of the spark current causes a breakdown of the insulation of the wires. This can cause some strange electrical behavior,

It is more often bad wires or corroded connectors. Make sure all the ground wires are connected properly to the block. There should be 3 of them. One goes to the lower passenger side of the block. One connects to the drivers side of the block right below the distributor and one is connected to the valve cover.

I had a faulty ground wire cause some really weird electrical voodoo.

Reply to
Ernie Leimkuhler

Thanks, I will check these things.

--Mike

Reply to
Mike

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