Engine rough idles on start up. it also started using some coolant. what do you think the problem is?

Rough Running Engine - James on Engines #2 - Bell Performance

https://www.bellperformance.com/blog/rough-running-engine

Apr 21, 2015 - When diagnosing an engine with a rough idle, there are certain things that must be ... If the problem does not reoccur, the codes will be erased by the computer. ... when accelerating the vehicle, which causes a higher fuel demand. .... it was water in gas...added added Gas LineAntifreeze/Water Remover.

I had a similar experience. Finally the car started overheating. Turned out the thermostat went bad and the radiator blew a leak. Had those replaced. Runs great.

check that the EGR valve is not sticking or has a vacuum leak. This valve will not operate until the engine is warm.

check also the engine coolant temp sensor (ECT). This sensor tells the engine computer that the engine has warmed up, so if it is faulty, it could be sending wrong information to the computer. If the sensor is disconnected, wires to it broken, or faulty in full cold mode, it will tell the computer that the engine is very cold, like -40F. The computer will schedule fuel for cold conditions. This is usually way too much fuel for a warm engine and it will rich misfire, idle rough, and be difficult to start warm.

The ECT has two wires going to it and is dedicated to sending information to the engine computer. It has nothing to do with your dash gauge that shows coolant temp. That sender has only one wire and is dedicated to the coolant temp gauge.

4.9 litre ?? you having a laugh its a 10ton truck engine not a pick up -global warming machine,remove the pump/sender unit and check the gauze filter also look inside tank for a something floating around ,i think the idles is not a related problem to the vehicle losing power but their is a possibility you could have a problem with the little vac operated thing on the fuel injector line that allows the fuel through only when the engine is running

try the control module

I hate to be the barer of bad news, but may be the head gasket.

My car started with rough idle. Then very hard to start in cold weather. Next started overheating, but no output from heater. Trickling sound from behind dash board. Overflow bottle overflowing.......

I replaced the water pump, radiator cap, thermostat, coolant, fan belts, power flushed the system. Nothing worked. Some research gave me the answer.

The head gasket leak was allowing exhaust gases to enter the cooling system, displacing the coolant. After use, as engine cools, coolant is sucked back into the system and coolant seeps into the cylinder. This gets worse over time.

First thing you'll notice is the rough idle as the spark plug burns off the coolant in the cylinder. (This is especially true at low temperatures.) If it is the head gasket, the other symptoms will follow as time goes by.

I would start by replacing your automatic air intake and throtle body sensor. Check these 2 things out and let me know.

tepfy

I don't know the model year? Key on engine off, use a gage and check proper fuel pressure. Then with key off, see if pressure holds for a bit? If it drops like a rock, check for a fuel pressure leak. If the engine is hot and trying to flood for some reason, your going to have a tough time. Any applicable trouble codes? Check your coolant temp sensor, only if testing leads in that direction.
Smell of your crankcase oil dipstick, does it smell like gas?