Hyundai Repair: Hyundai excel has low power, automatic transmition, hyundai excel

Question
My 87 hyundai excel hatchback will only go 40 mph up a hill.  1st and second gear will drive it up the hill but once it shifts to third it will not accelerate anymore and if I am going fast already it will slow down to 40 or below.  it has an automatic transmition.  I was told it may be my torque converter?  how can I fix this.  i might be able to get a turbo for it cheaply is this going to help? thanks for taking ht etime to answer my questions

Answer
You definitely have a performance issue with your engine.  Installing a turbo will probably have little effect until your engine performance problem is fixed.

Once common problem with '86-'89 Excels was clogging of the front catalytic converter.  If you take the pipe loose from the top of the manifold and it runs better, then that is almost certainly your issue.  Don't drive the car more than a very short test drive like this.  If you do, you'll burn the paint off your hood and may start a fire.

Also problematic were the carburetors.  The carburetors on these vehicles were so complicated that numerous problems often developed.

Additionally, I cannot tell from your description whether you transmission may be slipping in third gear.  If you have normal power in 1st and 2nd gear, but the engine tends to rev up normally and provide little power in 3rd, then your transmission is the most likely issue.

The torque converter is not your problem.  That would affect low speed operation more than high speed operation.