breakaway500

Looking for some help with a 1986 GT 5.0 Mass air conversion,B cam,long tubes. Car had been running fine for months,but now runs well while warming up,but as soon as it's warm, it won't idle smoothly/skips,hesitates..stumbles. Pull the spout connector,and it stops running erratically/skipping,and runs OK on base timing. Base timing is at12 degrees.With spout in,timing jumps to 20 degrees. Tried: new coil,new module,cap/rotor/wires/plugs. I swapped in a known good ecm,maf,tps,cts,iats. EGR is blocked and no air injection. Fuel pressure is 37-42. no codes (other than the ususal codes for missing air and egr) Any ideas??

rtintwo

Check your timing chain. Take the cap off the dissy. Put a socket and breaker bar on the crank bolt for the balancer and twist the crank back and forth. You are looking for the rotor to turn with the crank. About 1/4" to 3/8" of slop on the crank before the rotor turns is normal but if it is more than that i would change the chain.