Ok i did my own custom mass air install on my 86 f150 5.0. I used harness from a 92 ford mustang, an a9l ecu. i gotted started friday but it has a terrible miss. i Checked the ecu for codes and all i got were for all the soleniods EGR, canister purge, and this i know because i have not connected them. i noticed on the tach as i rev up the needle seems to bounce back and forth as if it were hitting a rev limter but im only at 3000 rpm. i checked the timing and sure enough my suspicion was correct it seems to retard the timing as i rev it to high or if i hit the trottle too fast. it wont rev past 3500 rpm. what is it? as i was looking on the harmonic balancer with the timing light it would start to advance to about 20 deg but then it would start to go back to ten deg i had another module so i swaped it and it ran a little better but not much. ive got an msd ignition but its all hooked up correctly. the only thing that im not sure of is on the harness it has a green plug on one end it had for two power sources. one for 12v tfi start and for eec i have these connected together and into the igition swicth. but not sure if that is correct. any help would be greatly appreciated!

 

I would go through the wiring harness with a fine tooth comb. I'd guess that the problem is all in the wiring. Check out www.pro-flow.com , they have a section for '86-earlier F150 mass air conversions. Also give this site a look: http://bjoern.brembs.net/cars/maf_conversion/

 

it was one damm wire! 12V for tfi start ONLY! i had constant power to it which explained the badd miss. all gone...... man! my truck hauls A@#! big time!