Intermittent spark as shown by timing light

[Mark]

I recently replaced the spark plugs on my '84 wagon. Just out of curiosity I hooked up my inductive timing light to check the timing since I hadn't done that in awhile. Last time I checked it was showing 40 degrees BTDC even though I manually set it for about 7 degrees (that was a whole other thread). It's still showing 40 degrees, but the flashing is intermittent on all wires. It flashes fine for maybe a second and then it stops for a few flashes. I swapped out the wires/rotor/cap with ones from my 81 sedan (which works fine with the timing light), but there's still the same intermittent flashing. I was thinking maybe the current in the wires wasn't enough to always fire the inductive light so I hooked up my old-style timing light that goes in series between the wire and plug. There was still the same intermittent flashing. I checked the coil resistance and pick-up coil resistance using the FSM procedure. Both were in spec. The car idles ok with the occasional stumble like there's no spark for a cycle every few seconds. This stumble doesn't coincide with the lack of spark as shown by the timing light so I assume it's just a vacuum leak/fuel/air mix problem. Has anyone had this intermittent spark issue before?

[irowiki]

Do you have a spare distributor to try?

[dlb]

yes, i have run into it on a few cars that ran with no issues. i think i even replaced the rotor, cap, wires, and plugs, but it would still happen sometimes. i'm trying hard to remember but i believe that when i used a different timing light, the flashing was fine, so i figured the problem was in the light. weird that you found the same thing with a different light though.

i agree that since the stumble doesn't coincide with lack of timing light flash, they are unrelated, and i also agree the stumble is probably from a carb-related issue.

[Mark]

I have another distributor, but it's in my '81 so I don't want to swap them out and re-set timing for 2 vehicles. Maybe later today I'll do some more checks on the distributor like checking the ignitor gap and voltage. I might go ahead and try a new cap/rotor as well.

[Petros]

you might also check all your connectors and where the wires are crimped into the back of each contact in the connector, and check the distributor internal contacts as well.

[Mark]

Well, I found the problem. I noticed that my battery posts are pretty corroded so I took a wire brush to them and the wiring connectors. Now the timing light flashing is smooth and my 40 degree BTDC issue has mostly gone away. Now the light is showing 20 degrees with the vacuum hoses left plugged in. I have the distributor manually set to 10 degrees BTDC, so with vacuum applied, 20 degrees seems somewhat realistic.
I also solved my "stumbling at idle" problem. It was one of the usual vacuum hoses disconnected hidden under the air cleaner housing.

I also found that a rebuilt distributor costs almost $400 after my 40% discount at Lordco. Even just the coil is over $200. I could probably get one for $4 or something at Rockauto, but the shipping would even out the difference.

[dlb]

holy doodle, that's an expensive distributor! lots of parts for tercs have really shot up in price over the last year.

[irowiki]

Junkyard ones aren't so bad.

[Mark]

holy doodle, that's an expensive distributor! lots of parts for tercs have really shot up in price over the last year.

Just for fun I should ask the local Toyota dealer how much a new OEM one costs. I'd guess around $800.

Junkyard ones aren't so bad.

Yeah, I definitely wouldn't buy one of those rebuilt ones when I could buy a whole hatchback Tercel for that price, take the distributor out of it and still have the rest for a lawn ornament.

[irowiki]

I have two that came with the 87 I bought that might work, I've never tested them. Could see about shipping you one?

[Mark]

I actually don't need one (but, thanks). I was in Lordco just looking for another part and out of curiosity I asked how much a rebuilt distributor cost. I was expecting them to say $60 or something. I was just keeping replacing the distributor as an option before I cleaned the battery posts and the problem went away.
During my automotive repair adventures this afternoon I created a couple more problems. I decided to adjust the valve clearances (stupid! Stupid!) since it hasn't been done in the few years I've had it. I adjusted the intakes to .008 and the exhausts to .012 when warm (according to the Chilton manual). I increased the clearance on most of the valves since I could only stick the feeler gauge in halfway originally. Now it clatters at idle. I keep ignoring my own motto: "Never, NEVER touch something that isn't broken".
I also replaced the radiator fan switch at the bottom of the radiator with a good one from my old scrapped '83 hatchback. My original fan switch had stopped working years ago so I wired in one of those adjustable thermostats with a probe that I attached to one of the coolant hoses. It mostly worked fine except once in awhile I had to take it apart to unstick a sticky switch. Now that I put a proper fan switch in, I can't remember what happened to the original wiring. There should be 2 cut-off leads somewhere in the engine bay, but I can't find them. I'll try again tomorrow when there's more light.

[marlinh]

It should be hanging near the front of the right fender well beside the rad.

[Mark]

Thanks, that's where it was. I had to look up the wiring diagram to find the wire colours and follow them from the relay. I had over-enthusiastically taped the wires up to another cluster of wires. I must have used about 2 feet of electrical tape so they were impossible to see at first. Now I just have to re-check the valve lash to get rid of the clattering.

[ARCHINSTL]

Interesting pricing from Lordco.
In the USA, pricing for WHOLE distributor:
AutoZone - Cardone rebuilt $240 + $38 core charge
Advance - ....".........".....$228 + $30..."......"
O'Reilly - .....".........".....$240 + $36..."......"

Maybe I could have a second career smuggling Tercel parts across the border?
Tom M.

[Mark]

Those prices are about what they quoted me for just the coil (after my discount). I think the igniter was less -about $100-and-something. The difference in prices North and South of the border is pretty crazy. I've often thought if I had to get some larger parts like struts or something it would almost be worth it for me to catch the ferry across the Strait of Juan de Fuca to Port Angeles and pick them up there. Plus I could have a mini-vacation. I know someone who did that for tires and saved a few hundred dollars for the same size and brand.