Cylinder 4 misfire & code P1416

Question

I have a 99 suburban with a 5.7 engine in it. It has a lift on it with 35 inch tires. While pulling our boat home from vacation the check engine light came on and started flashing. I had my code reader with me and I plugged it in and said it was cylinder #4 miss fire. Got it home and replaced plugs, plug wires, cap and rotor none fixed problem. Then I did a compression test on #4 and cylinder and along with #2 #6 and #8 all where 175 psi. Did some research and decided that it was more than likely my injector. While driving it to the shop that is 10 miles away white smoke started pouring out of exhaust. Pulled dip stick and had coolant in crank case. Got suburban to shop pulled heads and found that both heads where cracked with #4 intake being the worst cracked head. Got two new heads and installed on engine got it running again and still code came back. I didn't do injectors because I thought cracked heads where my problem all along, so I then installed injectors. Still code comes back. It only comes on while driving down the hwy at higher speeds. Usually around 4000 rpm to 5000 rpm code will set and flash service engine light. I've hooked scan tool to it and relearned cam and crank sensors with no change. While scan tool was hooked up could see #4 miss fire multiple times wouldn't code until driven down hwy. The other night while test driving it code p1416 came up. Don't really know where to go from here. Looking for any suggestions to help me with my problem. Thanks in advance.

Answer 1

P1416 Secondary air injection (AIR) System Bank 2

For P1416 you are more likely will have to replace the air check valve, you will spend more time and money in just testing this for its function this is at Bank 2 (where sylinder number 2 is located at.) As for the misfire , a injector is a solenoid if left unrepaired it tends to short out its ECM injector driver circuit,So this condition with the misfire can be more of a electrical condition than mechanical, you can also just see if works is to try a fuel injector cleaner (type you add in fuel tank)