Hi,

Picked up a '93 f150 5.0 for dirt cheap couldn't resist the deal. Engine is knocking - sounds like possibly from valves. The knocking is much more evident from inside cab, and increases with increasing RPM. The interesting part is it seems to be way louder when in drive. When it is in neutral or park, I barely hear it or cant at all. Engine will slightly buck when constant speed cruising at low speeds ~30mph. When I was listening to it (ebrake on, left in drive) I noticed there seems to be some vacuum lines disconnected and one is a vacuum source that is plugged with a red cap. Attached is the picture of the disconnected lines. The metal tubing line shown at top of pic is disconnected at the top and the bottom where the bottom is not shown in the pic. Is the knocking and vac line problem connected?

What do you recommend I check into first?

P.S. Engine is leaking oil. Seems to drip from rear main seal, but the oil pan is also wet and maybe from there. Tightened oil pan bolts today, so we will see if that problem continues.

Thanks for any help!

 

The upper steel nipple is for coolant to warm the throttle body, so it doesn't ice-up in very rare weather & engine load conditions. There's a corresponding nipple at the bottom of the t/b. Some people assume it hurts "performance"; others disconnect it because of leaks.

The other 2 are for the last section of the CANP system. Put a piece of vacuum line between them. Refer to the VECI label under the hood somewhere (usually above the master cylinder).

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For the knock: have an assistant rev the engine & hold the brake to make it loudest, while you crawl around listening with ~3' of garden hose, or a mechanic's stethoscope:

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A Haynes manual is a wise investment, if you READ it (cover-to-cover at least once). Read this caption before buying one:

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A clean truck (the working parts - not the paint) runs better & is easier to maintain:

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