bucking,hesitating

Before replacing the engine, start with the simplest things first. Has this been a problem that has come on fairly quickly or has it been a slowly growing one? Did it start after say... buying gasoline at a particular place or delving through a massive mud puddle? Anything unusual happen in the near past?

Things to check first:

A leaking fuel injector will cause the symptoms you describe. It will also wash the cylinder walls down with gas and lower compression significantly. Check the fuel pressure and do a cylinder balance test.

The ignition system will cause the symptoms you describe, but it will only cause low cylinder compression indirectly by an ignition induced misfire allowing unburnt gas to wash down the cylinder walls again. Check the ignition system components to make sure they're all functioning correctly.

A massive vacuum leak will cause the symptoms you describe, but it will not contribute to a low compression reading. Best to check for vacuum leaks to make sure.

If all comes back as functioning correctly, do a compression test... on the cylinders that read lower, squirt some oil into those cylinders and to the test again. If they read normal then suspect bad rings. The oil will temporarily provide the seal the rings aren't providing. Then follow that up with a cylinder leak down test to make absolutely sure.

The cost and time to do all this is small compared to replacing the engine only to find out the problem is still there and the removed engine was fine. Let us know.

[quote:0af444cbfd="joecool54"]I have a 1999 Ford Ranger 6 cyl, 3.0 liter, 2-wheel drive with 105,000 miles. Just recently, it has started bucking and hesitating. It has very little power when trying to accelerate hard or when driving up a steep upgrade. It idles fine, no smoke, has never used any oil. I don't hear any spark knock; it just hesitates, and has little power. I had it checked by a Ford Service center; they said it was losing compression in tw0 cylinders,which meant I shoulld replace the engine to the tune of about 4,000 dollars. My brother, a former mechanic, said it could be a number of things, such as a bad fuel pump or filter. Please help! P.S.--I would like to give a donation, but I could not get access to the site.(??)[/quote:0af444cbfd]

does it ever stall on you???
there are two fuel filters in the truck...one under the truck, drivers side...pretty easy to replace..its inbetween front and rear wheel. there is also a werid filter (they call it something else) its like a fuel retun...there is a filter inside...it sits right in front of the distributor cap. there is a retaing clip that need to be remove with reverse needle nose pliers . be carefull the clip will fly on you...make sure to cover it up with your hand and place some towel around it so it doesn't fly into the motor and get lost....becasue it will...not an easy clip to find...take off cover and clean inside and replace....i had a 2000 ranger that i had a hard time figuring out what was wrong...your prob. sounds similar...hope it helps ..raulromo34@hotmail.com