Coolant temp sensor is the one that tells the ECM that it is a cold engine. What is Code 1?

IAT is used for the ECM to compensate for air density.

N.E.O.

 

N.E.O.,

Thanks so much for the good info. I''ll check the coolant temp sensor next.

BTW, the Code 1 is what Haynes listed as normal for the ECM...that no trouble codes were there.

Thanks again.

 

There may not be a code for a problem with the IAC valve.

 

Since the IAC works fine when tested on the test terminal, I'm going to test the coolant temp sensor next. If the coolant temp sensor test OK, then I won't know what to do next, except to take it to a shop.

But I don't want to take it to a shop because I get more satisifaction from fixing these things myself. I am open to any other ideas you all might have.

 

Well, have your fingers cross, and hope for the best out come.

By the way, how does it idle when warm? Does it have fast idle that you can detect?

N.E.O.

 

Well, have your fingers cross, and hope for the best out come.

By the way, how does it idle when warm? Does it have fast idle that you can detect?

N.E.O.

It idles fairly well when warm. A tad low but definately not in the stalling range. And the A/C Idle Up thing works great. But, we can't use the A/C idle up thing in the winter for sure.

 

i've had a similar problem, but it would just idle low. i ordered a new IAC but i've not installed it yet.


i did however notice that CLEANING the iac out really helped alot.

you've verified that the pcm isnt controlling it by jumping onto the harness on a cold start with a multi meter and watching the output to the iac motor? or you're just assuming that since it works in the test....

 

Bitter,
Thanks for chiming in. I appreciate it.

I also sprayed B-12 down the throttle body and into the IAC intake hole. No diff.

I haven't tried to read the voltage on cold start from the harness yet. I figured that if the IAC worked fine by bridging TE1 and E1 on the test connector, that the ECM was able to send the voltage to open the IAC. But I could try that if you think it would make a diff.

I just tested the coolant temp sensor while cold and it is a bit low at 1700 ohms. Should be 2000 - 3000 oms. So it may be suspect. Tomorrow I'll test it hot and replace the coolant temp sensor if not in spec.

This is a real puzzle so far. I can fix almost anything on my old porsche 911, but I can't make this Toyota go!

 

What was the ambinent temperature when you test the coolant temp sensor? 1700 ohm corresponses to about 68 degree F. As the temp goes up the resistance decrease in the sensor. It could still be the sensor, if it is tell the ECM that it is warmer that the actual temp is. When it is at operating temp of 200 degree or so, it would be aprrox. 200 ohms.

N.E.O.

 

Quote: "What was the ambinent temperature when you test the coolant temp sensor?"

It was just about 68 degrees when the resistance showed 1700 ohms. I just tested it again with ambient temp just below 50 degrees and the temp sensor showed 3500 ohms. So at least in the cold range, the temp sensor looks good. I'll test it hot when my son brings the car back from school.

BTW, this morning, for the first time, it started right up and held its idle. It wasn't over 1000 rpm as I wished, but at least it didn't stall.

Question: When it's cool outside (under 50 degrees) should it idle at first above 1000 rpm? Like when I tested it on the test terminal?

Thanks!

 

Idle should probably be above 1500 rpm when the engine is stone cold. My Integra usually idles cold up near 1800 in the dead of winter.

 

the IAC is a $160 part, how much does the computer cost?

replace the small cheaper things first, i'd bet you could take the iac off and clean it out and get it to idle.