I'm trying to determine whether or not I have a real misfire or if it's just the cam overlap causing a slight surge. It occurs somewhat erratically between 1400 - 2000 rpm. It's not bucking, but more like a cylinder just isn't firing from time to time. There is no rhythm to it, or equal time between these little blips.
I've checked plugs (TR6's) and they all look identical. I've tried gaps at .035 up to .042. No difference. I have tried new plug wires, no difference. I have also moved timing from a high of 50 deg to a low of 19 deg. Moving timing down to 24 deg seams to be the best, and that's where my tables are set to now. I have also changed injectors, but that did not make any change at all. I have VE (custom O/S) error under 3% as well as MAF error under 2% using LTFT's and verifying that with the WB.
Nothing in the log is jumping out at me as the culpret.
I figured I'd log misfires next to see if I have a bad coil pack. I bought this car used, and it was professionally tuned by someone else. I pulled up a stock tune as the misfire detection DTC was turned off. Well now I see where the tuner has changed all the misfire tables by a factor of four times. I can understand why they were changed, as he also installed a cam and probably did not want the customer complaining about nuisance misfires from the cam install.
What should I set these table to? Stock, 2X, 3X or leave them? Is there a general rule of thumb for setting these with a positive overlap cam?
I was also going to attempt a cylinder load test, but not having ever done this, was unsure how do it. I'm assuming the best method is on a load cell dyno, but I don't have one or access to one. I'll need to do this on a quiet stretch of road. Any advice on that would be appreciated too.