Hesitates, shifts hard. And I have to really press hard on the gas to make it go

[Shrillcaleb153]

So a couple of weeks ago.. a new issue popped up on my vibe.. I would start it up and I would press on the gas and it would be very delayed and hesitate and it would shift hard and the code P0125 popped up (insufficient coolant temperature for closed loop fuel control) so I did some research.. and I replaced the thermostat and engine coolant temperature sensor.. and it seemed to solve the problem.. now it's doing it again and the light comes back on and I'm getting poor fuel economy because it's not operating in a closed loop.. it does this intermittently.. like for awhile it while operate perfectly fine in a closed loop and it will shift fine etc and sometimes it wont.. it will say open loop (low temp) even though my computer is reading the temp around 195 degrees it still says low temp.. any idea on how to fix this?


(UPDATE) it went away for a little while like a month or two but now its coming back as of april, I've also found out that if I bring it up to operating temperature and turn the car on and off again it will resolve the issue and close the fuel loop... why does it do that?

[andrewclaus]

I'm sure you've seen this list of possible causes:

Disconnected plug to the Engine Coolant Temperature (ECT) sensor
Possible corrosion in the ECT sensor connector
Damage to the ECT sensor wiring to the ECM
Defective ECT sensor
The engine is low on coolant or has coolant leaks
The engine coolant thermostat is not opening at the proper temperature
The ECM is damaged

I'd look for corrosion in the connection and harness next, then consider replacing the ECM.

[jolt]

I would make sure you do not have an air pocket in the cooling system. It is very easy to get air trapped in the cooling systems of the Vibe. Are you sure you got all the air out of the cooling system? The temp sensor needs liquid on it to read the temp of the coolant and not air that could be trapped in the system. Did you use something like one of these to make sure that there is no trapped air in the system: https://www.amazon.com/Lisle-24680-Spil ... B00A6AS6LY (watch videos and read the reviews). I am not sure if this fits your car, so you will need to check that for your self as I did not see where you state what year or engine you have.

I think you have a lot more troubleshooting to do and more information is needed before the cause is found. Air can be introduced into the cooling system by a cracked cylinder head or a blown head gasket, so right now we have no information about what was checked. Codes do not tell you what is wrong, they only give you a general area or what the computer has seen as data being out of a normal range. Guessing by changing the thermostat is not troubleshooting the issue to find the cause. All we know at this point is that the thermostat was changed and the problem is still there. Check your mechanical things first then move to the electrical.

[joatmon]

I also thought maybe an air pocket, since you had the system open.

If that's not it, the 2003 Matrix service manual lists the possible causes of a P0125 as:

• PCV hose
• Open or short in oxygen sensor circuit
• Oxygen sensor
• Air induction system
• Fuel pressure
• Injector
• Gas leakage on exhaust system
• ECM

although it seems those things might cause low engine temp, maybe not set that CEL while the engine does reach proper temp

I also attached the P0125 troubleshooting section from that manual

If you get it fixed, please let us know what it took