What is wrong when a 1989 4 L straight six runs great until it warms up and then it hardly idles and only the emission light is on but has been on for months?

1. What happens when the oxygen sensor goes bad?
2. What problems can a loose gas cap cause?
3. Why does my car stall after it warms up?
4. How do I know if my upstream or downstream oxygen sensor is bad?
5. Will loose gas cap cause rough idle?
6. What happens when the fuel tank pressure sensor goes bad?
7. Why is my car says tighten fuel cap?
8. How do you know if the idle air control valve is bad?
9. Can a bad thermostat cause stalling?

What happens when the oxygen sensor goes bad?

If your vehicle has a bad oxygen sensor, it could run irregularly or sound rough when it idles. A faulty oxygen sensor can impact your engine's timing, combustion intervals, and other essential functions. You could also notice stalling or slow acceleration.

What problems can a loose gas cap cause?

Probably one of the most satisfying codes your cars computer can throw is the "loose gas cap code." A loose gas cap will complicate the emissions system, which can create harmful vapor to be released into the air.

Why does my car stall after it warms up?

As the engine warms-up and starts burning fuel more efficiently, the choke plate begins to open, which slowly lets more air in and leans-out the air/fuel mixture. ... That extra fuel is able to be burned when it's cold (although not very well) but it is simply too much for it once it's warmed up, so it stalls.

How do I know if my upstream or downstream oxygen sensor is bad?

A decrease in fuel efficiency can be a telltale sign that an O2 sensor is not performing as it should. This can happen because of a fuel mixture that is either too lean or too rich. Such a swing in A/F ratio is a sign that an upstream or control sensor is faulty.

Will loose gas cap cause rough idle?

Therefore, a loose or a failing gas cap will bring about idling problems because of insufficient fuel system pressure. You can also have a rough idle from dirt and impurities that make their way into the gas tank's neck because the gas cap cannot shut off correctly.

What happens when the fuel tank pressure sensor goes bad?

Common reasons for failure:

Over time a faulty fuel tank pressure sensor will cause low fuel efficiency, trouble starting the vehicle and/or stalling, and eventually keep the vehicle from starting.

Why is my car says tighten fuel cap?

This message remains displayed if you ignore it and do not wear your seat belt while the vehicle is moving. If the fuel fill cap is missing or not tightened properly, you will see ''TIGHTEN FUEL CAP. ... If this happens, have your vehicle checked by your dealer as soon as possible.

How do you know if the idle air control valve is bad?

Common signs include irregular or unusually high idle speed, the Check Engine Light coming on, and stalling while idling.

Can a bad thermostat cause stalling?

Not the thermostat. A faulty thermostat will cause your engine to be slow to warm up or never reach operating temperature. Otherwise your car will run just fine. My guess would be a vacuum leak or something related to the idle control valve.