94 Tercel rough idle when cold - Toyota Nation Forum : Toyota Car and Truck Forums

atoyotchick · 11-12-2005, 03:27 PM

My 1994 Tercel runs rough when it is first started cold. Once it warms up, it runs smooth. What are some things I should start to look for that would cause this?

***Tercel GTS*** · 11-12-2005, 09:29 PM

Did you find out why the fan was giving you problems? They could be related.

atoyotchick · 11-13-2005, 08:05 AM

I was told by Toyota that I need a coolant temp switch. I had one of their techs point out to me where they thought it was located. He pointed to two switches around the thermostat housing and said that it was one of those two. I then had Toyota order me the part as I was going to try and do this myself. Yesterday I disconnected the two switches by the thermostat, and neither one looks like the switch that Toyota had me order. Now I don't know what I am going to do, I don't want to pay them to put in in but I may have no choice.

Do you think the temp sensor could cause the rough idle? Why would the temp sensor come into play when the engine is cold, I thought it was for when the engine was warm?

shogun6684 · 11-14-2005, 09:02 AM

Quote:

Originally Posted by atoyotchick

I was told by Toyota that I need a coolant temp switch. I had one of their techs point out to me where they thought it was located. He pointed to two switches around the thermostat housing and said that it was one of those two. I then had Toyota order me the part as I was going to try and do this myself. Yesterday I disconnected the two switches by the thermostat, and neither one looks like the switch that Toyota had me order. Now I don't know what I am going to do, I don't want to pay them to put in in but I may have no choice.

Do you think the temp sensor could cause the rough idle? Why would the temp sensor come into play when the engine is cold, I thought it was for when the engine was warm?

Had the same problem with my car. Is your check engine light on?? If it is, the most likely thing gone wrong is your Cold Start Injector Switch. Or I think its also called the Coolant temperature sending unit. When you engine is cold it requires a different air/fuel ratio than when its warm. So that sensor tells the engine computer what temperature the engine is so that it can have the right air/fuel mixture. If that sensor isn't working, the engine will start rough and sputter and stuff.

The sensor is located on the thermostat housing and is the one that's highest up and pointing toward the battery kinda. Clean it off, it should be a greenish color. Its really not that hard to take off, just need a spanner type wrench. Put some teflon tape on the new one and screw it back in and put on the connector and that should do it. Hopefully your problem is that simple!

atoyotchick · 11-14-2005, 03:47 PM

Thanks for the reply. I'm pretty sure the sensor needs replacing, but I cannot find the correct replacment for the life of me. Mine is white, the green one you speak of I found online and it has two prongs in it, versus the one in mine. The green one has a stem, mine does not. Toyota gave me the part number, however, when I look it up online and see its pic, it does not match mine. Growing very frustrated. I am putting in an image of mine, which I found online, but can only find it on foreign sites which makes it difficult to order. Also putting a pic of the one that Toyota says I need. If anyone can help.......please!

Here is what Toyota says I need.

http://www.motor-parts.net/en/showro...0015&cateid=82

Here is what looks to be what I have in my car:

http://hifine-auto.com/soft.asp?id=809

shogun6684 · 11-14-2005, 07:01 PM

Is your engine check light on?
The white one is the one facing towards the firewall of the car facing where the passengers would sit.
Your car has both of those sensors, one triggers the radiator fan(white), and the other goes to the engine computer(green). There is a third smaller one below the green one that I think shows the temperature reading on the instrument cluster on the dashboard. So there are three sensors in all.
Check your thermostat housing, look at the connectors and tell me what colors they are.
If the check engine light is on, its most likely the green one unless your radiator fan isn't coming on either.
Also, the connector for the sensor facing towards the battery, what is the color of the connector that suppose to go on the sensor?

atoyotchick · 11-14-2005, 09:23 PM

Thanks for the reply. Here is what I know:

The check engine light is not on. The radiator fan does not come on when the car reaches temperate idling. I have verified that the fan does operate, so I know the motor is good. The Toyota garage told me they "thought" that I need a coolant temp sensor. You are correct, there are three switches back in that area. The one that faces the firewall is the coolant temp sensor, which is white on mine. There is a green one like you said, and one other, I cannot remember its color at the moment. But I believe one of them does control the temperature gauge and the other is the coolant temp sending unit. I have the Chiltons manual for this car so I am certain that I have located the coolant temp sensor.

Last week I went to the Toyota dealership and had them quote me a replacement. They came up with about $75.00, which I knew was high. I asked them if there was another place I could pick up the part and the parts guy called the local NAPA himself and gave them the part number I needed. I went to NAPA to pick it up. They gave me a sensor with a maroonish plastic piece, and it did not fit the connector that my white one came off. Today I called the Toyota dealer and asked for the part# myself, and they gave me the following:
89422-20010
Well, if you go to http://www.motor-parts.net/en/showro...0015&cateid=82

you can see that its nothing like what mine looks like. So I have spent the better part of my day trying to find one that matches mine and that is when I found one in another country at
http://hifine-auto.com/soft.asp?id=809

One common thing I started to find was the part was also using the following part number:
89428-12160 adn 89428-12150. That is what the above link has for its number. When I did a google for those part numbers, I didn't find a consistent picture. One came up looking like the white one I have, another site with the same number had it looking different. So the only place I have visually seen what looks to be like mine is on foreign sites, which doesn't make for easy or quick ordering. I really don't understand why a simple sensor is so hard to replace!

shogun6684 · 11-15-2005, 11:10 AM

Call up some of those "pull a part" junkyards and see if they have any old corollas or tercels around your year. They may have the car and the part your looking for inside of it. If not, I guess you might have to pay the $75 for the green sensor from the dealer. I got my sensor through a junkyard.