Problems tuning TPS/Idle

[rbduck]

I have a 90 240sxK24E SOHCEverything standard.

I got my car back from an engine rebuild a couple weeks ago. when sitting still and revving to abou 2000 rpms.. it drops to 1500 quickly and then takes a very slow trip to about 750 RPM. I removed the AIV..no change.

Today, I pulled the TPS off and cleaned it. I measured the resistance from 2k ohms to about 10 kohme with a very smooth transition. I reinstalled it and set it to about 2kohms. Of course I did this with a completely released throttle. I cranked the engine and adjusted the voltage from the TPS harness to 0.49 volts. With these adjustments made, the engine idles at about 2000 rpm.

I tried the IAA adjustment and adjusting that with the TPS harness unplugged like the procedure states. Kill the motor. Plug the harness back in. Crank the car and then it's idleing at 2200 rpm.

So I loosened the TPS. moved it back until I got about 700 rpm and it runs pretty good. I again measured the voltage. It was about .20 vlts and with the engine not running, the full closed resistance was about 1k.

It's not what the book calls for but it works.

Oh, I did this from the DOHC procedure because there is nothing under the SOHC FAQ.

Thanks

[danton84]

There is a little set screw with an 8mm nut on the right side of the throttle body that controls how much the throttle is open. Try adjusting this until you get the idle you want.

[240canuck]

when your car is not warmed up it will idle at 1500rpm and very slowly go down to 750rpm when it gets warm. was the car at operating temp before you noticed this problem.

[rbduck]

Yes, when the engine is not warmed up it idles between 1500 and 2000 rpm. when it warms it settles at about 750 rpm. If this is the way it's supposed to operate I guess htere is nothing wrong. I bought this car when it had 141 kmiles on it. It now has 217 kmiles. THe other motor idled at about 705 rpm cold or hot. So, now with the new engine, I'm not used to it operating properly. ANother thing I thought was unusual is that I have to turn the TPS totally clockwise for it to even get close to a 750 rpm idle. If I adjust the TPS snd IAA per the procedure, I can't get an idle below 2000 rpm, much less 750rpm.

It still idles a little rough. I believe I know what's causing that. I have one injector that has a bit of the ceramic tip broken off. I intend to get a new set of those soon. I may also get a new tps. I've taken this one apart and cleaned it, but I'm sure this has been on the car since it was new and clean or not, the potientiometer is probably no longer linear.THanks for the replies guy...

[gtune4]

yeah, dont touch that set screw ever.you will kick yourself.leave that alone.