I've been fighting a rough idle and low speed light load misfire (not dead miss, RPM's vary from 760 to 850 at idle . Highway and full throttle is fine. Starts good hot or cold. Just installed new plugs, MSD wires, new ignition module and pickup coil. Did a ve learn for about 30 minites at idle and light load up to 2000 rpm's. Still rough. I checked the valve adjustment and ran a compression check, all 175 to 180#. Fuel pressure is good, ohmed the injectors, all 12.5 - 12.7. Pulled the plugs, 1, 3, 5 look good. 7 running rich 2,4 and 8 look good 6 looks rich. Injectors are ls1's I got from SLP about 12 years ago. AFR is steady over 1500 RPM's but all over the place at idle. Checked for vacuum leaks, replaced intake manifold gasket just to check for a vacuum leak on the bottom side, none found.

Motor is a zz430 clone with an lt4 intake. EBL Flash ECM so no MAF. Anything else I should check before spending the big bucks on injectors?

 

I bet the injectors on those cylinders running rich have high resistance after they get hot and will need changed out.