1990 Geo Metro, 3cyc, air, fuel injection

This is a continuing saga. I have replaced spark plugs, distributor, rotor and ignition wiring. Have cleaned the ERG and pvc valves. Have checked for air leaks on hosing. Have run cleaner through the fuel injector and added cleaner to the gas tank. For the most part, the car runs well. Now my problems is this.

When starting the car on a cold morning, and driving off before the car has thoroughly warmed up, the car runs fine until the car starts to warm, then the engine will miss and clog the spark plugs. If I pull over and let the car idle, the plugs will clean themselves and I can continue with no problem after that.

If I start the car and wait until the car has warmed up, say in 5 -10 minutes, I can drive the car and have no problems.

From the above, it seems that the problem is with the carburation / fuel mixture. in the old days I would say it was the automatic choke sticking. (In the real old days, I would pull the choke out until the car warmed up and then shove the choke back in. I learned to drive on a 1939 Ford :)) Since this is all controlled by the on board computer, can someone point me in the right direction and tell me what to check now?
Thanks,
Jim

Coolant temperature sensor. A very misunderstood sensor, one that doesn't get the respect it deserves. It plays a large role in telling the computer how to meter air/fuel mixture. Replace it.

-mechanicmatt

Where is this sensor located? I have looked for it and still haven't located its location.

Jim

Where is this sensor located? I have looked for it and still haven't located its location.

Jim
Are you getting a Check engine light on this car when this problem happens? a bad Coolant temp sensor or wiring to it should be throwing a code 14 or 15 on the car. 9C1 is correct though that it plays a big role in air/fuel mixture. I suggest you read the link below and see if you have any of these symptoms?.......The "Coolant Temp Sensor" is Located at the side of throttle body, this sensor measures the temperature of the engine coolant. The ECT is a thermistor, that is, as coolant temperature lowers, resistance increases and as it rises, resistance decreases. By monitoring the voltage drop of the coolant temperature sensor, the ECM detects the engine coolant temperature and that affects most systems under the control of the ECM.
The ECT will have 2 wires to it....Gray/White stripe and a Green/Black Stripe. Dont confuse this sensor with the one that is mounted in the Radiator hose goose neck......That sensor is for the temp gauge in the dash.

Code 15 Coolant temp sensor (http://www.automotiveforums.com/vbulletin/showthread.php?t=647882)

Engine Coolant Temp Sensor
http://i25.photobucket.com/albums/c83/MrBBody/ECT.jpg

Are you getting a Check engine light on this car when this problem happens? a bad Coolant temp sensor or wiring to it should be throwing a code 14 or 15 on the car. 9C1 is correct though that it plays a big role in air/fuel mixture. I suggest you read the link below and see if you have any of these symptoms?.......The "Coolant Temp Sensor" is Located at the side of throttle body, this sensor measures the temperature of the engine coolant. The ECT is a thermistor, that is, as coolant temperature lowers, resistance increases and as it rises, resistance decreases. By monitoring the voltage drop of the coolant temperature sensor, the ECM detects the engine coolant temperature and that affects most systems under the control of the ECM.
The ECT will have 2 wires to it....Gray/White stripe and a Green/Black Stripe. Dont confuse this sensor with the one that is mounted in the Radiator hose goose neck......That sensor is for the temp gauge in the dash.

Code 15 Coolant temp sensor (http://www.automotiveforums.com/vbulletin/showthread.php?t=647882)

Engine Coolant Temp Sensor
http://i25.photobucket.com/albums/c83/MrBBody/ECT.jpg
Thank you very both very much! I have never had the engine light to come on, but knowing I had a problem (see above) I went ahead and replaced the engine coolant temp. sensor. Have driven it around a bit and have had no problems, although tomororrow morning I will take it out again and see if the problem is still present. Cold mornings and first starts of the day affect the performance more than normal driving.

I just about had the temp. guage sensor out instead of the engine coolant temp. sensor. Thanks for the discription and the diagram. It was a great help.

Jim

Thank you GM for following up with the detailed info. :-) It may be noted that with OBDI systems, a sensor that has gone out of range but not failed completely may go undetected by the ecm, and continue to feed inaccurate information to the computer. Hope this works for ya buddy!

I replaced the coolant sensor a few days back but haven't had the time until this morning to try the car on a cold morning. Again, it ran fine until the water temp. started to raise, then the car misfired. I pulled over and waited until the plugs had cleaned themselves and continued on my way. No problem after that.

Reading the Chilton's manual, it mentioned that the O2 sensor also played a part in the air/fuel mixture. I decided to go for broke and bought a new sensor, just a little over $20.00. When I went to disconnect the connectors, (there are two on mine) the lower one was covered in oil from a leak. I opened it and found a little oil inside also. I cut the connecor out, and wired around it. Then took the car out again. Same problem. Tomorrow I will try to see if the sensor is generating any electricity. If not, I will replace it and see what happens. The connector I took out was supposed to be water tight, (and oil tight?). Not worried about the oil , which is an insulator but, I have cleaned my engine a few times with degreaser and then hosed the engine compartment down. If water was present in the connector at the time the car was running and there was voltage present from the sensor, then it might have shorted out. But wouldn't the engine light have come on? (The light is working, can be checked when the ignition is turned on and the car not started)

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