Troubleshooting codes

P0128 †ECT Below Thermostat Regulating Temperature

P0132 †Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 1)

For the first code suspect the thermostat is sticking open or someone removed it.

Better hope they did not remove it. I believe that is the 128 issue.
You need a scan tool for the other code to monitor the o2 voltage under conditions. You need to drive it full lean and full rich to make sure it is doing its job. If it is not, then replace it. If it is, then there is a control issue.

Roy

Sorry, I meant to say that the thermostat being defective is the issue. If you replaced those parts and the issue is still there, then there is another problem. You need a shop with a scan tool to help you and give you a bid for the repair.

Roy

A defective oxygen sensor won't set that fault code. Instead, look for a wiring harness that has fallen down onto hot exhaust parts and the wires have melted together. Two people have reported similar experiences recently.

The catalytic converter won't set that code either. When it fails to do its job, that is detected by the downstream oxygen sensor and a code is set related to converter efficiency.

What do you mean by "takes a little bit to start up"? Long crank time before the engine runs? Have to cycle the ignition switch repeatedly before the starter cranks the engine? How long is long?

Sounds like fuel pressure is bleeding down when the car sits. To verify that, turn the ignition switch to "run" but don't crank the engine. The fuel pump will run for one second. After a couple of seconds, turn the switch off, wait a few seconds, then turn it on again. Wait a few seconds, turn it off, then turn it on and crank the engine. That will cause the pump to run a total of three seconds which is more than enough to build the fuel pressure high enough for starting. If it starts right away, low fuel pressure was the problem. That can be caused by a leaking injector, leaking pressure regulator, or leaking check valve in the fuel pump.

You can also connect a fuel pressure gauge to see exactly what's happening. If the pressure drops to zero almost instantly when you stop the engine, suspect a cut or leaking o-ring around the pressure regulator. If the pressure drops over a period of an hour or longer, suspect a leaking injector.

My '88 Grand Caravan does that too. It always starts instantly in the morning, but once warmed up, it must crank about five seconds before it starts if it sits more than ten minutes. After watching how it acts for the last ten years, I figured out it's a leaking injector. In the morning that fuel in the cylinder has condensed to a liquid that doesn't cause a flooded condition. That's why it starts right away. When restarting it hot, not much fuel has leaked yet so the engine starts quickly, but longer than about ten minutes, and the excessive fuel vaporizes. That causes a flooded condition that has be be cleared out first by cranking. In addition, fuel pressure has dropped. Other than the first second after turning on the ignition switch, the fuel pump doesn't run to build pressure up until you start cranking the engine. Between clearing the flooded condition and building pressure until it's high enough to spray from the injectors, that can take a good five seconds of cranking.

There could also be a small piece of varnish or dirt holding the pressure regulator partially open. That would not be noticeable while driving, but fuel pressure will drop off instantly when the engine is stopped, and it will take a long cranking time to build back up. That can be intermittent depending on how the valve seats when the engine is stopped. About the only way to find that is by connecting a fuel pressure gauge and watching how it responds over many days. If you do my cycling the ignition switch trick, the pressure will only build very slowly during cranking if the regulator is leaking. It will build very quickly and stay up if a leaking injector is the cause.