MSefi.com read only forum (Jan.15,2018)

I have changed my ignition input capture setting from rising edge to falling edge due to a ms II 3.0 board mod I did to get a cleaner tach signal. Does this change my timing at all, i.e. the ignition offset? When I try to accelerate my a/f ratio goes lean, sometimes to as high as 21 and I am experiencing a lot of knock. A/F table is set to 13.5 in this area and timing is very conservative. Engine is a gm 4.3 v6 TBI. Thanks

Yes it will change the timing by half a tooth. Trigger offset is the distance in deg between TDC and when the input capture arrives. If you change the polarity it will arrive at a different time, so the trigger offset needs to be changed accordingly. When you set up your ignition, you should always check with a good timing light that it matches the gauge advance values at several rpms. Just change trigger offset until they match.

Thanks grippo. I reset the trigger offset. It appeared to be about 9 dgrees off. Pinging is gone. Did a datalog of the next drive and it ran well...except for spikes in my spark advance, fueling and in my rpm. Then started to run badly. AFR went low to 8.3, then really high. I have attached 3 logs-the first with the spikes, second low afr, third high afr. The last 2 logs are a real mess. I just had the throttle body off and removed the plug so I can adjust the idle speed. Have 12 psi steady, at the TB. Pulled the dist cap and checked. Looks fine. Found a short in wire from coil to spark advance module and repaired it. Replace one plug wire burned thru. Battery is not that good, goes dead if left for a week or more. Do see a couple of battery spikes but they don't coincide with the other spikes. Any comments or suggestions welcome! Thanks!

Found most of my problem tonite. My bad. somehow in the fueling setup it got switched to 8 cylinder for a v6. My LC-1 wideband controller is running at about 7.5-8.5 on MLV around 19 on the gauge in Tunerstudio (not moving). I will use the led to trouble shoot it in the morning. It was idling great though, for about 20 minutes.