walong95

I have a 1991 Mazda Rx-7, and recently I did some work on the cooling system because it had a leak. When I put everything back together the check engine light was on and it didn't want to start when it hasn't been driven for several hours. It usually takes about 2-3 times cranking to have a solid start. Also when I do get it starting and I attempt to drive it it bogs down and sometimes dies. Otherwise after I get past that I can drive it normally without issue and it will start right up once it has been driven and is still semi warm. Its fine when its at operating temp as well but the check engine light is still on.

I've looked for vacuum leaks as well as replacing the water temp sensor, and I checked all the connections to make sure that they were all grounded right. I'm at a loss, any thoughts other than trying to pull codes. I don't know how to do it (:/) I'm just wanting to fix my baby. Thanks!

satch

iTrader: (1)

Checking codes:

There is a single wire in a check connector near the leading coil. Ground wire to the negative battery terminal and turn key to on.

walong95

FC3S rx7 starting issue - YouTube

this is what it is doing, and thanks ill try that.

walong95

Ok so I pulled to the code and it was for the water thermo sensor, I replaced it and cleared the cars computer and it is still not working right. Any suggestions, someone told me that I can only replace the thermo sensor through Mazda in order for it to work right, is this true? or what? I'm just concerned that this will cost about $55 in order to replace.
-Thanks

jfantis

Not exactly true but possible. You can easily check the switch with a multimeter. My first guess would be wiring or grounding. Thermoswitches are simple devices and all you need to know is the resistance at the current temperature. There is normally a scale of sensor temp vs resistance in the workshop manual. Per Mitchell 68 F should read 2300-2700 ohms and 176F should be 200-400 ohms. Also make sure you replaced the switch that goes to the ECU not the fan. I believe the one you are looking for is on or near the water pump housing.

satch

iTrader: (1)

Usually an error code means a poor connection and not a bad sensor. So, you replaced the sensor but you probably didn't check the wiring in the plug. Best way to do this is to check the voltage at pin 2E (Green/White wire) of the ECU w/key to on and you check the voltage w/the engine cold and then the engine fully warmed up. Should read 2 to 3 volts DC cold and .3 volts completely warmed up. Sometimes one of the two wires in the plug is pulled back and thus a poor connection to the sensor.

walong95

what would that mean for me if there is a poor connection?

satch

iTrader: (1)

The car would not run properly.

walong95

is there a way to fix it?

satch

iTrader: (1)

You can't tell if the connection is poor by just looking at it for the voltage reading at the ECU needs to be taken to be able to tell one way or the other as described.

walong95

i got a high reading while it was hot, 4.9 Volts DC

satch

iTrader: (1)

This tells you that one of two if not both wires in the sensor plug are not properly mating to the sensor. This happens quite frequently. You could try pressing the wires from behind and thus pushing them into the plug. There could also be a break in one of the two wires as well.