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91 Toyota 4 runner dramatically loses power on highway, fine around town

My 91 4 runner, with 192k miles, has very scarily lost power twice on the highway. She gets to about 50mph and then drops to 40, 30, 20 rapidly. First time I had her towed because I didn’t want to take the chance I couldn’t arrive safely at mechanic. 2nd time, I just sat for awhile with her running, and tried and succeeded to get her to mechanic. First time, mechanic thought there was some boot loose around the fuel line.Second time, mechanic is stumped.

She has new fuel & air filter (and battery + leads); catalytic converter tested fine. Had a tuneup less than 5k miles ago.While I feel safe driving around town, I am terrified of highway driving and need help getting her fixed so I can resume highway driving.

How did someone “test” the catalytic converter? Or do you really mean to say that the exhaust flow was checked?

“Tuneup” doesn’t mean anything specific. Specify exactly what was done 5k miles ago.

The fuel pressure needs to be checked under load - not static key on/engine off, and not idling. It needs to be checked under the same kinds of conditions that lead to the power loss.

Catalytic converter was tested using a back flow test - they drilled a hole (not sure if it was in front or behind the cat. converter) , used some kind of gauge and pronounced it fine. They then plugged the hole back up (welded)

Tune up was changing spark plugs (I learned to my chagrin that’s all it involved, not like the old days when it included changes filters (oil, fuel, gas); checking fluid levels, checking tire pressures, etc

How does (either the driver or the mechanic) “check the fuel pressure under load”?

Did Anyone check the ignition coil?

I will ask the mechanic if anyone checked it. For the record -also just got new starter, battery & terminals for non-starting problem.

Locate and disconnect your EGR valve and see if that cures it…