starts ok, then loses power, then ok up to 30mph...
Iíve got a completely stock 1996 Ford F-350 with a 7.3 liter Powerstroke engine with 301,000 miles on it. Itís been a pretty reliable performer for quite a while but recently a belt tensioner flew apart and I drove it home and ended up getting it a little hotter than usual because the water pump wasnít pumping. The gauge never got out of the normal range and it didnít actually overheat. Not to long after that, and possibly just a coincidence, it started doing this weird thing where it loses power, and if I run it over 30 mph it starts to miss. Then it nearly stallsÖ If I let it sit and idle, it seems to catch up with itself and then it will have lots of power and torque for probably 15 seconds and then it starts the cycle over again. It will bog down, run rough, lose powerÖ Then if I let off of it, it runs fine again.
I did replace a fuel hose that was leaking a little, and the fuel filter in the center top of the motor. Iíve also used a couple pieces of regular fuel line on top of the manifold instead of that expensive OEM (blue) fuel line, so Iíve wondered if Iím sucking air in or the hose has degraded or come apart and blocked something up. I put a relay pump on it a couple of years ago. Iím hoping Iím not looking at a high pressure oil pump or an injector pressure regulator. It acts like this very consistently and Iíve been driving it short distances, but need to get it resolved.
Iím a fair gasoline engine mechanic, but am pretty clueless and a total novice on diesels. I donít really have a diagnostic computer easily available for this one. Anyone have any ideas?