Testing Spark Plug Leads

[Z2TT]

Hello,

I have decided to test my spark plug leads, to make sure they are not causing my idle problems, and just general maintenance in case they need replacing. So far I have learned that I have to test them with a multimeter, but how many ohms should I get, many websites seem to contradict each over.

Is this a valid way of testing to see if the spark plugs are in good condition, or is there no way to find out if they would be breaking down under high voltage when the engine is running.

Thanks

[Sam_Q]

I find as a rough rule about 1k ohms is normal for every 10cm although my memory might be off as its been a while

[Z2TT]

Thanks,

Any other feedback?

[oldcorollas]

unless they are broken, you won7t get much result between godo and bad.
of course if one or two are wya different to the rest, thenyou have issues.

the resistance of th elead is not that big a deal. it is only when they are broken that theinside is a problem.

more of a problem is when the silicon outside degrades and absorbs moisture. that is harder to test.

you could warm them in oven or something for a while and see if it helps?

or just swap new leads and see if it helps.

[Gttwinturbomk3]

The type of ohms reading is just determining what way it shows you the results on the multimeter readout. The longer the plug lead the higher the resistance the shorter the plug lead the lower the resistance. I think? Someone?

[Z2TT]

So from what I have gathered so far there is really no way to know if the lead is faulty or not.
Or is there more to it?

Thanks.

[oldcorollas]

measure the resistance of the frickin things and then start wondering.... sheesh

[TC1600]

Check the resistance, I can't remember exactly how much resistance is ideal, but as long as they are consistent they should be fine (obviously longer leads should be slightly higher readings but you can work that out). Also flex the lead while checking resistance as this can show up intermittant loss of continuity. Don't forget a visual check also, the terminals at each end should be clean and not corroded (goes for the terminals on the coils/distributors and plugs also), and check the insulation for crossfiring, which leaves a white residue where the leads touch each other or a ground point.

Don't forget to keep leads separated, not cable tied to each other.

Usually symptoms of leads breaking down is a misfire under load, as this is when the most load is placed on an ignition system. A weak spark may be ok at idle or light load, but under heavier loads it may not be enough to ignite the mixture.