Spark

[Longshot270]

I'm making an educated guess here. But I dont think you'll notice if there is a single bad plug by watching the spark reading. Like Jack said, that number only show the advance in timing. I've noticed that everything from RPM and APP to MAF readings can cause the timing to go all over the place. WOT can bring it down to less than 3˚ but while cruising down the road it can hover around 30˚-35˚. With a spread like that I would imagine it's hard to be sure. I bet that having one bad plug would show up more on RPM which you can obviously feel, but a rough idle can be caused by many factors. That would be an interesting idea to log the spark and idle before and after someone is going to change plugs for refrence.

[bambo2888]

Originally Posted by longshot270

That would be an interesting idea to log the spark and idle before and after someone is going to change plugs for refrence.

good call. maybe i try to start logging some data, for im planning on taking the dive soon here with the lisle tool and tsb.

[Longshot270]

Originally Posted by bambo2888

good call. maybe i try to start logging some data, for im planning on taking the dive soon here with the lisle tool and tsb.

Cool, just dont forget to have different kinds of driving in similar conditions. I usually do one slow acceleration and then one WOT. That way you get a wider range of data. It also helps to make a second session later if your able (for verification). And on the PID's pick the most valuable 5. Here are 4 that are usually pretty important SPRK, RPM, MPH, LOAD and either APP, CHT, IAT, MAF, and AFRP for the 5th.