Truck ins chugging or missing at 40 mph - 1993 Chevrolet Suburban

Hi, what do you mean by chugs at 48 mph ? Doesn't it go any faster then 48 mph, does it lose power, bog down when you press the gas pedal to the floor. Does it have a misfire , that makes the vehicle buck and jerk ! Is the check engine light on or any other lights for that matter ? How many miles are on this trailblazer ?

Did you check for OBD Codes?

Check & test the battery?

Look at all data on a road test?

Either the exhaust converter is clogged
You have little fuel pressure
Or a dozen other possible issues

run the fault codes. check the serviceability of the cat converter as it may be broken inside and blocking the exhaust

use a scan tool?
got DTCs? errors.?

motto: scan first , wonder 2nd.
is chugging misfire?

if its a petrol get coil packs cheked does it do it under load mor when accelarating ir pulling up hill this would cause it to miss

What speed are you going when it chugs?
It could be as simple as a bad spark plug or a spark plug wire/boot grounding out.
When spark plug boots get old, the rubber cracks and lets voltage arc out the side and to the engine instead of through the plug.
This will be most noticeable when trying to maintain a speed of over 40 mph, or under mild acceleration.
The reason for being noticeable at this speed/acceleration level is that the transmission torque converter will be locked, transferring the vibration from any engine miss straight through to the wheels.

I see you like replacing computer sensors. Did anybody try something really high-tech like performing NORMAL MAINTENANCE? You know, high-tech stuff like replacing a fuel filter?

Try swapping the fuel filter, it's a cheap fix and might just be the problem! Change the air filter also. good-day !

Check your transmission lock-up. It's programmed to come in at at 40mph. You can replace the lock-up to come in at 60mph or better.
Or you may have some ignition wires going bad or distributor cap has crack in it.

are you sure it is a miss and not a shutter or transmission kicking in and out?possible cause could be tps sensor losing signal at this spot is check engine light coming on?