Question about an ignition miss on rpm curve

[TURBOZ]

Will in ignition miss show up on the rpm curve in a data log? I notice the rpm jump backs from say 5000 to 4950 then back to 5K. Does that mean there is a miss?

 

[bobc455]

Possible, but I doubt it. You would feel the engine stumble, too.

What's probably happening is best explained by an analogy.

Lets say your heart is beating at 70 beats / minute. If you take your heartbeat for 15 seconds, you might get 17 beats. Well since 17X4 = 68, you would report this as 68 beats/minute. On the other hand, you might count for 15 seconds and get 18 beats. And since 18X4=72, you would report 72 beats / minute. If you graph this out, you might wonder why your heartbeat is jumping up and down, when in fact it is steady at 70 BPM.

In other words, don't be concerned by little jumps in the displayed RPM, the ECU can handle it!

-Bob Cunningham
bobc@gnttype.org