Toyota corolla gt-s ( AE86)

hello my friend has a 1986 toyota corolla gt-s and a while back the head gasket went and now we have replaced it but 2 big issues have come up.

!. when going to start the car for the first time you turn the key it cranks, it fire, but just sputters and doesnt run and itll do that the first 5 or so key turn then it gets to where it catches it self barely and runs but the idle goes up and down quickly and doesnt stop doing that until it warms up

we already made sure all the vaccum hoses are hooked up right and the cold start injector is getting fuel

2. it has an error code for the water temp sensor but we cant get the comp to clear it we disconnected it for a couple minutes (didnt work) took out the stop fuse ( didnt work) and then we left the battery unhooked overnight and the stop fuse ( didnt work)

could you guys help this is start to frustrate us alot.

by disconnecting it i mean disconnected the battery

any ideas?

This sounds like it could be a number of things, especially if the car was sitting a while - like it might have been with the head gasket going “a while back”.

If it’s an '86, it probably has a carburetor, and they tend to gum up when a car sits for more than a few weeks.

Another thing that comes to mind is that when you replaced the head gasket, it can be very easy to get the cam one tooth ahead or back, which could cause all kinds of starting/driving problems.

If it were me, I’d start by checking things like compression and spark on all the cylinders, and methodically go through the major items that could have gone bad with coolant in the cylinders and old gas in the fuel system.

this car is fuel injected it has the dohc 16v 4 cyl engine

Gee, not to state the obvious but:

The coolant temp sensor is what tells the computer the engine is cold so it can adjust the mixture and idle speed to compensate. If it’s not working, it’s not suprising at all that you’re having cold start problems!

Do you have any reason to doubt that there actually is a problem with the coolant temp sensor?

weve tested the sensor twice according to the manual we have and the sensor checks out fine. now we havent tested the connector for continuity yet due to rain.

One other thing to do is actually take the sensor out and make sure it’s wet. If the coolant level is low or if there’s air bubbles in the system, that’ll throw off the reading enough to confuse the computer. Did you change the thermostat and radiator cap (and the coolant) at the same time as you did the head gasket?

I’m usually not one to throw parts at a car, but as the CTS probably costs all of $15, I might be tempted to change it anyways just given the trouble code.

no we left the cap and thermostat on but we did change the coolant

Are you sure you checked the correct temp sensor? This car has two, one that runs the temp gauge and the other is for the computer. The computer sensor has a 2-wire connector and the temp gauge sensor has a 1-wire connector.

ah ok thats probably the start injector time switch which is right next to the temp sensor ill loook at that later when my dad gets home