Hi. Recently bought a 1995 Chevy Blazer LS ( 4WD, 4 Doors, Fully loaded, 4.3 Vortec V6 ). It runs like a beast on the freeways and city streets. However I recently took a trip up to Big Basin with a few friends and the truck wasn't fully loaded, but going uphill around 51 MPH and 2500 RPM the engine felt a huge loss in power and started using a lot more gas, had to floor it accelerate. I have another 4.3 and never had this issue spring up.
I had my mechanic do a full inspection of the vehicle after I purchased it. The truck has 140k miles on it. The differentials are clean, fluid is relatively new, transfer case and transmission are the same, clean and fluid is relatively new. The Exhaust manifolds are in good condition and secure, the cat and muffler are both new. It just had a full tune up and received a new fuel filter a week ago. It also has a recently replaced EGR valve and the intake is spotless.
I replaced the OEM air filter with a K&N filter that fits in the stock intake. The radiator was recently flushed and has new coolant. We cleaned the fuel injectors as well. The body does not have a single ding and the paint looks new, the engine is immaculate and belts are not worn. The injectors do make a ticking sound on acceleration.
I tried reading a few other forums about similar issues other owners where having with the 1995-2002 4.3L engine. It seemed there where a lot of other similar stories with a corugated intake hose clamping when the engine was hot uphill and denying the engine air and forcing it to use more gas. I do not have that intake hose but the issue is very similar, about 50 MPH and 2500 RPM uphill. If anyone has any ideas please just throw them out there. I hate gremilins