rb20det high idle

[daniel_wads]

Hey guys my rb20det in my s13 is idling wayyy high. I've tried adjusting the idle by tightening the screw by the aac valve and its all the way tight... im sure its not a vacuum leak BC I've tested for some and can't seem to find any I've timed it to 15 degrees and tried adjusting cas, but nothing seems to get the idle any lower =/

[fliprayzin240sx]

Either your AICV is fucked up and its letting too much air in or you have a vacuum leak. I'm willing to bet you have a leak more than anything else. What did you do to test for leaks?

[daniel_wads]

Oh i also cleaned out the iac valve. But to check for leaks i sprayed carb cleaner on any vacuum lines I can see but couldn't notice any change in idle. I'll try harder tomorrow to find leaks though.

[Pandapants]

Make sure your tps is set correctly; it should emit about 0.45v when closed. Make sure you have no vacuum leaks, and how do you know your timing is at 15 degrees, if you idle is off? did you adjust the iacv correctly? You have to disconnect it first before you turn the adjustment screw, this closes the valve completely, preparing and assuring a proper adjustment.

[daniel_wads]

I'm pretty sure my tps is set correctly BC it has marks on it from the previous owner, and the throttle responds best where it is set right now. I don't have a multimeter so i can't really check the voltage. I read somewhere that you have to unplug tps first before you adjust the idle screw. Idk maybe they were wrong. I'm sure its timed right BC all the timing marks line up and when I turn everything 720 degrees it still lines up. Does this mean its timed correctly? I've only timed one other car before lol

[Pandapants]

By making sure your tps is within spec, you can assure yourself that the throttle plate is not being held open by the sensor and causing an irregular vacuum or idle. When adjusting your idle, you have to make sure the throttle valve switch has its "idle contact point" ON, you can insure this by disconnecting it (not the tps). More accurately, the voltage reading on the throttle valve switch should read 8-10v at idle and 0v when depressed. After that you can then unplug the aac; this closes the unit completely allowing you to accurately adjust your idle from scratch.

You should really invest in a multimeter. The motor relies on misc sensors to function, and if the sensors are malfunctioning, or receiving an improper input, they will not perform well.

If youre talking about the markings on the timing belt matching the cam and crank sprockets, then that is setting the valve timing, not the ignition timing. The ignition timing is different and can only be accurately acquired if your idle is stable and "normal" before using the timing light. The ignition timing changes as the speed changes, and if your idle is different than what is specified by the fsm when acquiring and setting the ignition timing, then your ignition timing reading will be off.

How do you know your idle is high? Do you have a functioning/accurate tachometer? Consult? What kind of vacuum are you seeing at idle? There can be no load on the motor as well (all lights and accessories off, and steering wheel straight) when determining your idle.

[daniel_wads]

Hey thanks for the info its really helpful. im new to working on rb20's lol. When I get off work tomorrow I'll try adjusting the idle the way you say to do it. Where is the throttle valve switch located? What color is the plug? Oh and I do plan on investing in a multimeter soon haha.


Hmmm that's interesting I didnt know there was two types of timing thx for the info.

I don't have a tach hooked up yet but I can hear its idling too high. I'm not sure how to tell what vacuum im at. How do I check? And yeah I made sure there was no load on the motor.

[daniel_wads]

Ok so I installed my boost gauge and my vac at idle is about 18-20.

is that about right?

[daniel_wads]

ok i tried adjusting the idle by unplugging the lower plug from the tps and then unplugging the iacv (brown plug). i can adjust the idle lower but it idle searches for a little bit then wants to die... and then when i plug the iacv back in, the idle jumps way up and idles really high... also on a side note, when i go hard on the throttle and decelerate it dies. i read somewhere that this can be caused by a bad iacv. do you think this means a fucked up iacv? amd maybe these two issues are related?

[Pandapants]

The throttle position sensor is the 3 wire plug that runs about 2 inches off the tps unit. Leave that plugged in. The throttle valve switch is located on the tps unit itself. It should be a 2 wire plug that's perpendicular to the throttle body and "J" pipe. Try unplugging that.

[daniel_wads]

ok i just tried unplugging the throttle valve switch and the iacv, but after i adjust the idle, and plug the IACV back in, the rpm's jump way up still. do you think i might need a new IACV?

[Pandapants]

http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed1.jpg
http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed2.jpg
http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed3.jpg

For a consult:
http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed4.jpg
http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed5.jpg
http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed6.jpg

This is you; no consult:
http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed7.jpg
http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed8.jpg
http://i151.photobucket.com/albums/s125/kagabe24det/Rb%20swap%20info/idlespeed9.jpg

[amnash]

so what ended up being the issue?? i have the FSM printed out and have followed the exact steps you posted in the FSM pictures above.

but when you plug the electrical back into the aacv the idle jumps way high.
and the next step in the book after plugging it back in is make sure the idle speed is maintained at specified value. doesnt say what to do if it doesnt stay..