How much is a tune up on a 97 nissan maxima if the parts were already bought

Given everything you have already done to it I would suggest checking for a faulty distributor or coil. Have you checked the timing? I had almost the exact problem in a previous vehicle and it ended up that the top of the coil wire was arching onto the exaust manifold intead of firing the cylinders. I found this out by having someone rev the engine while I inspected all the plug wires and coil wire for external sparks. Good Luck keep me posted.

None of what you replaced was necessary

Who replaced those parts & why,no testing?

If the thermostat is 6 or 8 years old, you just
replace them on all your cars

That is were you fill it up but you will have to get a funnel to do so.

remove screws - they is probably one around the door handle (carefully pry out cover piece) - and underneath any big round (1 inch diameter) plastic screw hole cover - then carefully pry off.

Spark plugs, spark plug wires, air filter, throttle body cleaner, alcohol and a toothbrush to clean your electrical connectors with.

yes it's always best to tune a car up atleast once a year that way your burning fuel all the way and your getting the best fuel milage and performance

This could be water in the gas lines or, you may have wire and plug issues as well. I would take this car in for a full scale tune up. make sure they check the distributor points as well. Changing the fuel pump wouldn't hurt at all.

Every 30,000 miles you need an air filter, every 60,000 a fuel filter, every 100,000 spark plugs. That's it.

throttle position sensor,or egr valve,also check your air filter,if this helps please gine me a fix ya vote