Misfire, but no DTC's?

[Fabricator]

the tricky part here is car is not on the road, only load testing works, fully loaded car or up hill flogged (but fails parked, so that too is ok.)
so test the car parked, and gun engine hit, and for 3 key on cycles, hot. repeat 2 or 3 times see if DTC set !!! Will try this, but think driving would be better

to see if MAF works, but do clean it first.
if still fails after clean maf
test injectors, next. or pro clean them . like seen , reverse flowed, untrasonic cleaned.
https://www.witchhunter.com/


i just added this, and applies to P0300, 301 upto P0304 ( 1,2,3,4 code means only this cylinder fails.
so put more gas in take, over 15%
and run the test 2 times, hot engine gun throttle hard, parked, and see if P03xx codes POP, or P0171 or PO172 (rich lean pop)
even flog the throttle from 2000 to 4000 RPM (or if bogs still try)
or try to hold throttle steady at 3000 RPM or 4000 for say 10 seconds, see of DTC's POP, the 300s series only POP for steady cruise,



bad fuel
bad maf (dirty
vacuum leaks huge. (super huge, that is do not believe)
dirty injectors or filter.
I assume spark plugs new. at the tips white now or jet black carboned.?

even this cheap HARBOR FRIGHT(SIC) tool can loop scan the 02 front " Graph live data onscreen" feature set is very good to have. like this. (not sold there now, the have better ones , and brand changed) but is clear what is going on.
the tool is slow (or ECU is) and does not see all "crosscounts' but we know it does. on newer cars with CAN buss and faster ECu this plot becomes super perfect. 3 points on each swing is best.



great 02 demo here, even many cheap tools can do this even $50 (ask) ignore bank 2 comments and 2rear sensor but do listen to all S1 comments for sure
idle, cruise, gunned throttle and fuel cut modes(deceleration) lazy 02 or dead or stuck lean are all things to check and graphing 02 is the only way to do this.
https://www.youtube.com/watch?v=jRa752CeNvg

even my relic PALM can do O2 live, see? 1996 tool, I made with custom software, from friend.
http://www.fixkick.com/sensors/chev-live009.jpg