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I have a 1991 f150, I6 300. The other day I replaced the valve cover gasket and the upper intake to lower intake gasket which required the upper intake manifold to come off as well as all the vacuum lines and electrical connections. I disconnected the battery first just like the manual said. Everything went good. The
next day while driving I noticed a pinging sound(doesn't sound like valve pinging). It only happens when the engine is under a slight load and a small range in rpm, or if I give it a little gas. Similar to what the EGR valve was doing before I blocked it off, except for the hesitations. It runs good otherwise. Did I mess something up with the injectors maybe? It ran good
before worked on it. Any ideas?
Recheck all your vacuum lines and fittings , you may have a leak .
Those plastic hoses and fittings can crack without breaking apart.
Also check torque on the maniford bolts and check for leaks around the new gasket. Good Luck.
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