I buy and sell prius, usually blown headgasket I dont usually mess with coils and plugs when I usually already know its headgasket, but the codes are usually cylinder 1 p0301, anyways got the headgasket replaced and got the car back and it is misfiring in cylinder 4 only. Also it does not misfire right at start up like usual but it starts misfiring about 1 min after its started. The mechanic usually cleans out the egr and the intake manifold but I am not there I dont know if it wasnt good enough. my question is would a clogged or not fully clean egr cause misfire, even though i dont think so but would you suggest swapping coils to see if it goes to another cylinder? spark plugs were change any other ideas?
the coolant tank also has pressure build up but not a whole lot I just think the headgasket was not done right. But I guess I will try to swap coils
The EGR would cause a misfire at idle if the valve were stuck open. It should be fully shut at idle or very close, not allowing any exhaust through. A simple test for this would be to loosen the pipe between intake and EGR valve and insert a putty knife to block the flow. Snug bolts down, start it, and see if problem disappears. If it does, the vehicle needs a new EGR valve. If it doesn’t, your problem lies elsewhere.
