TPS question

[rbduck]

ka24e sohc...1990 240sx..engine with 2500 miles since remanufacture

I've had some problems with idle. The engine idles great when cold but idles at about 1700 rpm when at normal operating temp. I've read just about all the valve in the engine. I just read a couple of posts the raise questions. The TPS has a switch that makes when the throttle is fully closed (theoretically) There was also the mention of a "soft idle switch" and a "hard idle switch" Someone please explain what they are and what the difference is???

Now I've went through the tps adjustment procedure a number of times. The potentiometer tracks linear from 2 to 10 kohms. I can adjust the voltage anywhere between the .45 and .55 that I want. When I adjust the TPS like this, the switch in the tps never changes because the throttle doesn't close nearly enough. To position the TPS to a point that the switch does change, I have to twist the TPS completely clockwise. Of course, this completely defeats the voltage adjustment. So, if some of you guys have some knowledge as to how this is supposed to work, please let me know. This idle thing is driving me nuts. I know I have adjusted the TPS and IAA per the procedure I found in the FAQ, but something is missing here. It may be the space between my ears.. thanks for any help you can be to me.

Thanks again

[neil90s13]

I about freaked when I read this--I haven't checked the site in quite a while, but I'm having the exact same problem. If I unhook the connector that goes to the solenoid (that has the AAC label on it--green connector) the idle drops back to 900-1000 rpm. What's worse is when the engine is cold (with the AAC connected) it idles at 900-1000 rpm then jumps to 1600 when it's warm (seems to be the opposite of what it should be doing). So, I've been driving with it disconnected and the car runs like crap. If I use the AC I have to rev it before I take off or it will die. With the AAC connected, the idle will jump to 1600 rpm when I come to a stop (but right before I come to a complete stop--makes me wonder about speed sensors, etc) Sorry for the length here, but hopefully someone can help.

[rbduck]

An alternative to keeping the harness disconnected is try rotating/moving the tps totally clockwise. There is a switch in the TPS that either makes or brakes (I havent checked with an ohmmeter to see which). I think this is the switch that's mentioned in a couple of messages I've read. I think it cuts the fuel when the switch changes states. I do know that on my car, when I have it set like that the car seems to run and idle great. But, the voltage I'm supposed to see when tuning the TPS is way off from specified normals (.45 to .55volts). Actually I'm pretty sure it cuts the fuel. I notice that if I'm driving and let off the gas, there is a sudden drop in rpm (caused by the fuel being cut). Tomorrow afternoon, I'm going to put the TPS back into this position as I prefer it over the constant 1700 rpm.

I've found it surprising from the collective knowledge I thought was on this forum, no one knows how the TPS functions. Thhat's the reasom I asked the questions the way I did. Does anyone know what the switch does? Is it supposed to do anything? I will find out what it's for and let you know. Anyway, hopefully that knows will read our posts and help out. I'm just frustrated with the whole thing. Have a good on.

[sil80drifter]

Maybe you should have posted this in the "mechanical help" section, there are actual mechanics there who know all about that stuff.

sil80

[rbduck]

I've been so intense in these forums I completely forgot about the mechanics forum...thanks for advise sil80..it's already posteed there