my truck doesn't have one. I'm i also noticing it feels different when driving it cold with some very light random bucking. I'm wondering if it has to do with the truck running too cold all the time.

 

why would you not have one? it is a cheap part, cooling system is designed to have one...

 

not sure why....i bought it this way. i heard some ppl take them off because they think is better it runs cooler all the time in warm weather. in my case the temps are cool outside (dec?) and I may be running into some issues.

I know in some trucks/cars the temp readings can be crucial to the rest of the ecu party. Not sure if is the same for this 22R-E 1989 truck though.....

 

Your truck probably has a rad problem, most likely plugged up and rather than fixing it properly the previous owner probably removed the thermostat to prevent the engine from coming up to operating temperature and eventually overheating because of poor coolant flow through the rad.
If you don't run a thermostat, your engine will not warm up to the proper operating temperature, because of that your temperature sensor will never send the proper signal voltage back to the ECU to let it know the engine has warmed up. If the ECU thinks the engine is still cold then your fuel mixture will be rich, your timing will be for a cold engine and it will never smoothly or efficiently.
Besides that if you live somewhere where it is cold in the winter....you're going to freeze your a** off because without a thermostat the engine will never warm up enough to push hot air out of the heater and defroster.

 

I think you hit it right on.

The radiator does have some problems and it has 3 small tiny pin holes near the cap. I see small amounts of coolant coming from there after the truck sits for a few days. But it does not leak while operating hence the reasson why I have't address yet. But if I end up adding a thermostat, it wil probablyl blow.

okay so is important to truck runs at its operating temp. i will have to get the rad and thermostat taken care of.

 

without thermostat the biggest problem and most people dont know is your engine block,it will eat your cylinders uneven,causing a lot of ridge at very low mileage.thats why i use one of at least 160 in the tropic of P.R.

 

A new radiator is not that much if you get an aftermarket, I tend to buy new than used on radiators since you don't know what your getting used, like buying used speakers! something you just don't do!!!! :}LOL

And get a dealer available dual element thermostat, they work awesomely<Is that a word? It should be a word :}LOL

And get new hoses too from dealer, cooling system is the life blood of the engine!!!!

 

The thermostat just controls how hot your engine will get before it starts cooling. If you don't have a thermostat everything should work fine, but you won't have much of a heater.

 

This is probably a true statement for carburated engines, but for fuel injected engines not so.
When a fuel injected engine is cold it runs in a open loop condition. It does not look at any of the sensors, it starts and runs based on the base fuel and timing maps stored in the memory of the ECU and the cold start injector is used to add extra fuel. The cold start injector is controlled by the start injector time switch, but the ECU can overide the start injector time switch at anytime by providing the cold start injector an alternate ground path through the STJ terminal of the ECU. This decision is based solely on information obtained by monitoring the coolant temperature sensor. (THW) As the engine warms up the ECU monitors the signal voltage coming back from the coolant temperature sensor to determine the engine operating conditions at any point in time. On a cold engine the ECU uses a base map and the cold start injector and sets the timing to allow easier starting. Once the engine warms to a certain point the ECU will switch to closed loop mode where it uses other sensors to fine tune the engine operation, but the ECU is always looking at operating temperature to decide which base timing and fuel map that it should use. Once at operating temperature it uses fuel maps and timing for optimal performance. The O2, Air temp, knock sensors, etc. are secondary sensors and they are used to fine tune the fuel and timing once a fuel/timing map is chosen based on operating temperature. After making an adjustment to fuel and timing, the ECU monitors these sensors to verify that the changes it has made are okay and if not it will fine tune the fuel and timing for optimal performance. I'm speaking of an engine that is not under load and is warming up at idle. Under load air flow meter comes into play, but at idle the ECU knows how much air enters the engine through the bypass.
Bottom line is temperature is everything to a fuel injected engine!

 

well,its the opposite,with engine cold it operate in open loop.

 

You are correct!
I read that post several times and still never noticed that mixup!
I guess that's why authors have proof readers!
Edited now correct!
Thanks!

 

Very good explanation Hadmatt. I had an idea how the system works but didn't know how to explain it.