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

Also the vehicle has oth overdrive and drive gears and it did this in both.
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Hmmm after some serious deliberation we "think" it may be the transmission Torque Converter. It's really only "noticable" up steep hills but after the vehicle is nice and hot and been running for an extended period the acceleration bogs down a bit noticable when jumping onto a freeway.

Few other owners of the same vehicle said around 130k miles with the OEM tranny even after continued maintenance and fluid changes it just sort of wears itself out around then. Nothing is made to last forever. Will update later. It looks like it is just starting to show signs of wear and isnt throwing up any codes at the moment.

 

It turned out to be a mix between the air intake gasket which had just started to develop a minor leak and the old torque converter. Luckily the transmission did not need a complete overhaul, just the converter replaced. Also there was a ton of carbon built up on the lower planar of the intake, had to actually chisel it out. It had only left a keyhole size hole.