Car has weak spark- need help finding source

[Bryan LaTraverse]

95 Corolla DX wagon 1.8L

Car has had trouble starting after it warmed up, had to wait half hour to restart it after driving so it could cool down
Figured out the car was getting a weak spark all the time, and little to no spark when the car got too warm. Replaced the distributor and spark plugs but still having the issue, any suggestions?

Topic

[Mike]

The ignition coil is what generates the spark, so if it’s present at the right times but weak, the coil is usually to blame. It is a voltage amplifier. If only a portion of the coil inside it shorts, it will partially amplify the voltage so the spark will be weak. The point being that a failed ignition coil isn’t necessarily completely dead, there are degrees of failure so to speak.

You didn’t mention replacing the ignition wires, which can also cause a weak spark if the internal resistance is high, but that’s not common. Usually faulty wires will leak the voltage externally and cause an outright misfire, and that usually happens when they’re wet. If you wash your engine and if misfires, worn out ignition wires or a distributor cap that isn’t sealing out water are the usual problems. If you can wash your engine bay and it runs normally afterwards (including a test drive), then you can pretty much rule out distributor and ignition wire problems. The coil is also normally immune to water as long as the ignition wire between it and the distributor is sealing properly. If the coil is sensitive to water and the ignition wire is new, then the coil housing is cracked or open somehow and thus can be considered failed.

[Bryan LaTraverse]

I replaced cap and coil when I did distributor
So would the next step be ignition wires? I’m assuming by that u mean the ones that go from cap to plugs?

[Mike]

[quote=”blat88″ post=137135]I’m assuming by that u mean the ones that go from cap to plugs?[/quote]
Yes, and the set should also include a wire from the coil to the cap

If the spark is still weak after replacing the whole ignition system, then the normal size wiring or connector to the coil may be corroded or damaged somehow. The other real longshot is that the grounding strap between the engine/trans, body, and negative battery terminal is corroded/worn/damaged.

[Bryan LaTraverse]

Ok thanks for the help, appreciate it. I would assume not all the ignition wires would go at once though so if all 4 are getting weak spark can I rule them out?

[Mike]

[quote=”blat88″ post=137137]I would assume not all the ignition wires would go at once though so if all 4 are getting weak spark can I rule them out?[/quote]

Correct, although it’s an assumption like you said. The wire from the coil to the distributor of course will affect the rest of the system after it equally. My professional experience has been that weak spark is a coil problem. Obviously we’ve been over that, but I’m just throwing it out there for the sake of having more information. It’s very unlikely that you’re new coil is defective to the same extent the old one failed, but I’ve seen things that ridiculous before. Keep us updated on what you find.

[Bryan LaTraverse]

I’m assuming I have a new wire from coil to cap, I got a whole new distrib already put together. The car will crank with no spark then after 2 seconds it’ll get a weak one (it’s orangeish not blue and inconsistent) then fire up. How would I go about checking grounds? I also had some oil spilled over the engine could that have messed with wires?

Spark is bad on all wires

[Author]

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