Car hard to restart after engine is warm - Sprint Chevrolet Cars & Trucks

replace coolant temp. sensor , disconnect coolant sensor plug after engine is at running temp. ,shut engine off then restart ,if engine starts fine, replace coolant sensor

Replace the crankshaft sensor and the cam sensor. I had the same problem. Good luck.

I think the engine coolant temp sensor or coolant thermostat has failed.

Hi...how old is your battery...sounds like a possible dead cell. Have you been losing engine power by any chance? How many mile on vehicle?

The first thing to check is to make sure the engine is not overheating. This will make it hard for the starter to turn it, due to the engine tightening up.

The way to test a fuel pump is to put a pressure gauge on it in the morning when it is cold when you have the problem. If the pressure is low then your fuel pump isn't working when it is energized.

If it is high, but it is still hard to start, look at a fuel injector being plugged up.

You may have a leaky fuel pressure regulator located on the LH side of the engine on the side of the fuel rail. The internal diaphram can leak fuel which then gets into the vacuum line attached to the regulator. From there the leaking fuel travels through the line and gets into the intake manifold causing the motor to be slightly flooded when you restart it. The regulator is round, about 1-1/2" diameter, and about that long and has a small 1/8" vacuum line attached to it. After the engine has been off for a few minutes if you remove the vacuum line from the regulator and find even a trace of fuel in the line then you've found your problem. Typical symptoms for a leaky regulator are: Starts fine cold and will restart fine warm if the engine has only been off for a minute or so. Restarts hard warm if the vehicle has sat for several minutes or up to an hour. May produce a bit of black smoke during the warm/hard start.

If it starts fine when cold or will restart after it cools down and run until the engine warms up, have your TPS (Throttle Position Sensor) replaced. I have seen quite a few lately that will "warm" up and cause the car/truck to gradually run rougher as the engine compartment heats up and once it sits and cools off will restart and run again. You can go to auto zone, advance auto, etc and have them run a free diagnostic test on your car and tell you for sure if any TPS trouble codes are stored

Have your fuel pressure checked. It sounds like you have either a fuel pump problem or your fuel filter is clogged.

try changing your egr valve first