More problems, help!

[scruffboy]

O.K., so I got the check engine light to go off by replacing the broken Coolant Temperature Sensor. But now my car idles at 2000 rpm's! When I disconnect the sensor, it will drop down to 1100. Not the 800 I'm used too, but better. Can I drive without this sensor? When I connect it, the car drives all jerky and stuff, but disconnected, it drives much better. Does anybody have any idea what is going on here? This is driving me insane. Someone please help me.

Thanks,

Scruffboy

[Bill UK]

Did you replace the sender unit with the correct type and was it running ok with the old unit you glued together.?

[scruffboy]

Yeah Bill, I replaced it with one that looked exactly like it, same set up. The old one looked so coroded that I'm not sure it was really working, maybe just enough to keep the engine light off, I mean I saw no metal to metal contact on the broke one. Can I run without the temp sensor? Maybe I just need to have my idle adjusted, and then hook it back up. I'm just not sure. I don't know if this could mean anything, but I did not wait for the coolant to cool all the way down before I replaced it. Could putting it in without waiting long enough have destroyed it? Thanks Bill UK, I appreciate you responding.

Scruffboy

[mrnickleye]

The heat did not harm it. It sits in hot coolant. I suspect other problems.

"I" would first try disconnect the negative battery cable for a few minutes, to clear the ECU. Then I would hook it up and start the car. Normally you need to drive the car for a few city miles, and start and stop the engine a few times, let it idle a few minutes, etc.

Doing all this, the ECU re-learns. Normally after this, the idle settles down to 700-850rpm.

[scruffboy]

I had already done everything you mentioned. I disconectted the negative battery cable for a few minutes figuring that would clear the memory. I drove around in stop and go traffic several times. I raced the engine a little bit hoping that that would "settle it down", but no go. In the morning I have to hook it up to get it to turn over. Then I pull it out just enough so that there is no connection. The Check Engine light comes on, but the idle drops to 1,000. Could the fact that we are having a cold snap here have any bearing on this? It's been dipping into the upper 20's to low 30's overnight. Anyway, I have this really good "Ultra Copper" gasket maker and I used it to put the old one back together. This weekend I will swap it out and see what happens. If I can't resolve this issue, can I go to my own mechanic, or do I have to go to a Toyota dealer? I'm not used to cars with computers and diagnostic codes and such. Would my mechanic, who I trust and is very reasonable, (I found him by word of mouth) be able to hook this car up and find out what's wrong?

Thanks,

Scruffboy

[Bill UK]

It does sound like your new sender unit may have the wrong resistance values, did you obtain this from Toyota ?

[scruffboy]

I bought it at Autozone, and I was thinking about that also. Maybe I should have went to the Toyota dealer, but I was trying to save money. Today I went for a fairly long drive, with the unit un-hooked, and it drove smoothely, but on the way back I decided to connect it, figuring a long drive at decent speeds might have "knocked its memory back", kinda like what Mr.Nickleye was alluding to, but it went back to running all jerky and lopy. When I got in the driveway I started really revving the engine, red lining it. That got it to drop a little, it went from about 2,200 rpms down to about 1800 rpms, but that is still way off. How do you adjust the idle with an EFI engine anyway? Is there something mechanical you can do, or does it have to be hooked into a diagnostic machine? I have no experience with them.

Thanks for your help guys,

Scruffboy

[mrnickleye]

1) a good diagnostic technician can easily work on MKIIIs, and should be able to find the problem.

2) I to am thinking the new sensor may be the wrong one.

3) The idle is adjusted by the ECU, which looks at all the data from all the sensors. The ISC valve on the intake manifold is what 'actually' controls it.

4) perhaps there is some other cause to your high idle.

5) it is a 'one step at a time' process of elimination.

[Bill UK]

This looks interesting may be useful for future reference.

http://www.forum.mkiiisupra.net/showthread.php?t=12132&highlight=TPS

[scruffboy]

That was a great site Bill UK. Mr.Nickleye, I have to say I think this unit is sending the wrong data to the ECU because this is my routine. In the morning, I have to connect the sensor to get the car to start. Once the car has idled for a few minutes it starts revving high. I then get out and slide the sensor till it disconnects and immediately the rpms drop and I drive off and it drives like it always used to, very good. This is a pain in the ass but after Christmas I will get my sensor from a Toyota dealer. I'm sure it will be expensive but I guess I learned the hard way - you get what you pay for. I want to thank you two fellas for seeing me through this. Sometimes folks who know what they're doing don't waste a lot of time someone like me, so let me wish you both a Merry Christmas and a Happy New Year! Hope 2007 is good for the both of you.

Thanks,

Scruffboy