1988 ford f150 4.9 300 misses on occasion

Asked by Dec 15, 2013 at 08:56 PM about the 1988 Ford F-150 XL Standard Cab LB

Question type: Maintenance & Repair

its slow to start at times. misses when the temp is rising to the normal temp when driving
at 55 for a while as soon as i let off the gas it clunks and i can smell fuel. i put a new
tank/sending unit fuel filter. also new plugs wires and ignition coil cap rotor i took it in to
get the fuel injectors professionally cleaned just cant figure it out

1 Answer

21,845

Usually, the Exhaust Manifold warps and takes the intake manifold with it causing a vacuum leak. Since it's fuel injected, there's no chance of the old "rich-in-the-center" cylinders. At least once a year, you should check the torque on the exhaust/intake manifold bolts. The same fasteners hold both of them on to the side of the engine. The weight of the 2 manifolds hanging off the side of the engine, and the expansion and contraction of a nice cool intake manifold and very hot exhaust manifold cause the gaskets to fail. There's a couple of ways to fix it: Replace the Intake/Exhaust gasket and have the two manifolds milled together for a flush fit and replace all of the fasteners OR go aftermarket (if you can still find them) and get separate manifolds - preferably with a Stainless Steel Exhaust manifold or Header.

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