1985 Nissan Maxima - 3.0 Liter V6 - Many issues - Need HELP!

[wallacengineering]

I just joined up here to ask you guys for some help. I am barely 18 years old and I am very experienced with mechanics due to having 2 years internship experience with a Ford mechanic shop.

I own a 1985 Nissan Maxima Sedan, a road-going classic version of the slightly famous 2-door rally racing version. Where as the rally version carries a turbo, my version carries voice alerts, power everything, automatic transmission, and a very comfortable ride.

Now as you can see, the car is now 26-years-old. However, it is sitting at only 198,000 miles. There are many issues with the car, though; and even with my experience I am too afraid to touch the car until I am completely sure as to what I should do.

The problems are listed below:
- Even on warm, sunny days, when the engine is first started it will die unless you hold the throttle until the internal engine temperature is in the normal operating range.
- The idle is off and so the previous owner has the throttle line propped up rather than properly adjusting the engine. This is the one thing I do not know how to properly adjust
- When I first bought the car at 175,000 miles, it got 21 MPG city and 25 highway, now it gets 16 city and 20 highway
- For a 3.0 Liter 6 Cylinder 180 BHP engine, it is EXTREMELY slow and unresponsive. It feels as if it has under 100 BHP remaining, even though all 6 cylinders run correctly and the spark plugs are new
- It is time for it's final oil change before 200,000 miles. Because of this reason, even though the spark plugs are fairly new I want to replace them with high-milage specialty ones

How would you guys respond to these alarming problems? What kind of oil and spark plugs would you recommend for me?

[Nahkapohjola]

Originally Posted by wallacengineering

I just joined up here to ask you guys for some help. I am barely 18 years old and I am very experienced with mechanics due to having 2 years internship experience with a Ford mechanic shop.

I own a 1985 Nissan Maxima Sedan, a road-going classic version of the slightly famous 2-door rally racing version. Where as the rally version carries a turbo, my version carries voice alerts, power everything, automatic transmission, and a very comfortable ride.

Now as you can see, the car is now 26-years-old. However, it is sitting at only 198,000 miles. There are many issues with the car, though; and even with my experience I am too afraid to touch the car until I am completely sure as to what I should do.

The problems are listed below:
- Even on warm, sunny days, when the engine is first started it will die unless you hold the throttle until the internal engine temperature is in the normal operating range.
- The idle is off and so the previous owner has the throttle line propped up rather than properly adjusting the engine. This is the one thing I do not know how to properly adjust
- When I first bought the car at 175,000 miles, it got 21 MPG city and 25 highway, now it gets 16 city and 20 highway
- For a 3.0 Liter 6 Cylinder 180 BHP engine, it is EXTREMELY slow and unresponsive. It feels as if it has under 100 BHP remaining, even though all 6 cylinders run correctly and the spark plugs are new
- It is time for it's final oil change before 200,000 miles. Because of this reason, even though the spark plugs are fairly new I want to replace them with high-milage specialty ones

How would you guys respond to these alarming problems? What kind of oil and spark plugs would you recommend for me?

Read the link below, check/correct the issues mentioned. I guess problems gone?

Denso -or- NGK platinum/iridium plugs only.