Hello all,

I have an '87 with the 4.9l 4spd. The truck has recently started making a strange grumble/ air under pressure escaping noise. I can't really call it a knocking or ticking noise. It only does it when the engine is under load. If I drive it super easy and shift early I doesn't seem to do it (or maybe I just cant hear it.) But if I hit the gas a little hard up a hill it grumble/ pssst's. If I put in in neutral or hold down the clutch and rev it it doesn't make the noise. I got under the truck today and checked the muffler and intake and exhaust manifolds all looked OK. But I didn't take a wrench to them. I recently completed an AMSOIL oil change, because that what the previous owner used. Please help, I don't want my FORD to blow up.

Thanks,
Steve

 

Check for a ruptured EGR valve diaphragm. Error code scans also. Takes some of the guess work out of it.