Toyota Sera - Trouble Starting and Then Struggling Engine

Forgot to mention it's a manual and if you need more information about the engine because it's quite a rare car, try going to

Any further info need though I should be able to answer.

Thanks again

Steg

If the vehicle is fuel injected, check the engine coolant temp sensor and cold start enrichment system, whether it is an enrichment system for the injectors or a cold start injector. Check for vacuum leaks and for a leak in the intake tube between the air filter and throttle body. Also check base ignition timing.

There was a gap between the fuel injection system and the air filter where the pipe hadnt been secured properly. I have fixed it but the car is still the same.

I wouldnt know where to find the "engine coolant temp sensor" sorry I don't know a hell of a lot about cars. And if I did I wouldnt know what to look for to see if it was broken or not. If you can give me any advice about this, possible location and what to look for if it's broken.

The radiator has a small leak in it, but I didnt think that this could lead to a problem like I'm having. But your mention of coolant made me think I better mention it.

I've had the car for almost a year now and never had a problem like this before, it's just come on all of a sudden.

If I cant find a problem on my own I'm going to have to get it to a garage and I really can't afford that sort of expense at the moment. Any help would be very much appriciated.

Thanks

Steg

I forget what the original symptoms are but a leak in the intake will cause driveability and hard starting problems. Check the intake hose carefully for other cracks, especially on the underside or back side where it would be difficult to spot.

The coolant temperature sensor is generally on or near the thermostat housing. Follow the top hose of the radiator back to the engine - there is usually a bulge where the hose connects to the engine, and the thermostat is in the bulge and the coolant temperature sensor will be somewhere near the bulge. It will be a threaded cylindrical piece with one or two wires coming out.

I forget what the orignial symptoms are, but if the coolant level is low and there is an air pocket in the system, the coolant temperature sensor might not be able to sense cooclant temperature.

On an engine with a carburetor, the carburetor mixes air and fuel for the engine to burn. When the engine is cold, the choke restricts air flow so more fuel enters the engine for a given amount of air, which raises idle speed. This is known as an enriched mixture. Once the engine warms up and the choke comes off, then ratio or air to fuel is adjusted for optimum performance.

On an engine with fuel injection, the coolant temperature sensor tells the computer whether the engine is cold or warm, and if it is cold, then the computer will enrich the fuel mixture until the engine warms up. There are basically 2 ways to enrich the mixture in a fuel-injected engine. One way is to have an extra fuel injector known as a cold start injector, which sprays extra fuel while the engine is cranking. The other way is for the computer to tell the regular injectors to spray extra fuel. To be honest, I have no idea which system the Sera has, but if the enrichment system is not working, then the engine will struggle until it warms up.

Another possibility is that there is a vacuum leak that seals itself up as the engine warms and the connections expand.

Thanks for your help Ray, but I think you may be under the impression that the problem only happens when the engine is cold. It happens regardless of engine temperature. Don't know if this will have any effect on your prognosis. :-)