So I just finished replacing a head gasket and when I went to start it up for the first time I heard a knock but other then that the truck ran fine. But today I took it back apart and readjusted the rocker arms thinking I put then to tight. After putting them to the torque that was said in my Ciltons book. And I finished that I put it all back together and started it again the knock was still there and now it was idleing at over 3500 rpm and butterfly vavles were completely closed any suggestions. I have a 4.9 on a 1991 F150

 

Scary when it Idles that high ha. Pull engine vac,clean tb and iac. U can test the tbs with out taken it off. Pull codes first and if it don`t have any you have a air leak. Actually you probably get a o2 code on it.