eric240sx

Hi Everyone, Okay! After adjusting the throttle body, throttle cable, calibrating the TPS, and setting the AAC, I finally got it to idle at 900RPM! It was definately the way the throttle body was reassembled. I had a pretty big gap allowing air past the plate. For anyone that ever has an idle surge/fluctuation issue with an RB25DET, or probably any RB, please do the following: Perform a vacuum test leak. My favorite method is to use a smoke test, but you can use "start yah bastard" fluid around gaskets, vacuum lines, intake manifold, etc. . . Clean Idle Control Valve or AAC (Clean with carb cleaner, brake cleaner, or whatever else parts cleaning solution). Also ensure the set screw is properly adjusted to allow air in or to block air out. Turn on the engine and turn the screw in or out to hopefully adjust your idle at the correct RPM. Don't be afraid to turn! Make sure TPS (throttle plate sensor) is between .45 - .48V at idle or calibrated using an aftermarket ECU software Ensure throttle body plate is fully closed, check throttle plate screw. The screw must allow the plate to fully close Ensure your throttle cable is allowing the throttle body plate to fully close, not too tight, not too loose. Thank you everyone for all your help! Looks like all I need now is to dial in my tune. I will be consulting @robbo_rb180 for guidance.

Correction, I inserted the two bolts and now there is a very very very, like hair wide or less slit on both sides. Before it was a pretty big gap compared to this. I’m excited to try it tomorrow!

Hi everyone, I ended up running out of daylight, the family came over today. But I was able to remove the throttle body and yes, there was air getting through, I have adjusted the TB screw and aligned the TB plate. This is the current close position. MUCH MUCH better. I put a light behind the TB in a dark room to see how much light was getting through and this is fully closed without biding. It’s just a slit at the top. Is this good? Fun Fact: I tightened the two bolts a little too hard the first time and ended stripping one when removing. I ended welding a screwdriver tip to take it off

Hi @robbo_rb180, Thank you for taking the time to look at my tune and explain why the timing was ranging. I'm currently at work but once I get home, this is my current plan: 1. Remove the intercooler piping to look at the TB plate to ensure it’s closing properly. 2. Make sure my TPS is set at .45V at close 3. Recalibrate TPS 4. Ensure my throttle cable isn’t too tight 5. Load new tune file and log I'll report back tonight. Thank you all for helping me sort this out. It is never required and yet you take the time to do it.

Hi everyone, The research and videos I’ve watched, also with @Duncan suggestions, it all seems to point towards the throttle body, TPS, and AAC. But my AAC is working. Plus, after forcefully closing the TB all the way, the engine idled at 900. Tomorrow I will do the following: 1. Remove the intercooler piping to look at the TB plate to ensure it’s closing properly. 2. make sure my TPS is set at .45V 3. recalibrate TPS 3. ensure my throttle cable isn’t too tight I will keep you updated

Hi @Dose Pipe Sutututu, welcome to the forum! Yes, I have recalibrated my TPS to read 0-100. I’m going to be looking for internal leaks and see if that can repair the issue. This is my current setup. It looks more like an RB26

This is a good pointer, my base timing is all over the place because my idle is funky. Look like when I cut out all external air supply, it was happy. Hmm. I’ll be researching how to detect internal leaks for the RB as we continue to brainstorm : ) once I achieve a stable idle, I’ll do the timing again. It’s hunting time

Hi @Duncanand @joshuaho96 So… looks like I read this too late. I rechecked the AAC and it’s 100% in tip-top shape. The bolt Duncan is describing is one I had to remove to paint the outside of the throttle body. For this, I used regular automotive paint, no powder coating. Once I reassembled, I returned the screw to what I thought it was set at. But today, I screwed the bolt on the AAC all the way down, and fully closed the TB, I DEFINITELY felt the binding of the plate. But the car stopped fluctuating and dropped RPM to 900 as @robbo_rb180set it up. It ran as it should, even the air to fuel went to 14.5-14.7at idle. I checked timing at this point and it was running at about 10 degrees, not the 15 I set on the ECU and crank speed timing. Once I changed the offset to match 15 at idle, rpm rested at 1,300 still higher than what @robbo_rb180set. However, the fluctuating stopped. In order to open the throttle body at this point, it did require a bit of a push to unbind the plate and have it move freely. However, as soon as it was free, the fluctuating idle started again. I will be looking for the procedure to appropriately set the scree. Yikes! Not really sure what to do at this point, but I’ll check for internal leaks. Thank you for the video, @joshuaho96!

Hi! I removed the ACC, going to verify all components are installed correctly. The throttle body doesn’t close fully, it is slightly open. Should it be closed? I can try closing it further. I don’t believe I have a cold start valve, just the AAC.

Hi Duncan, Yes, I have turned the screw all the way in (currently set at this) and backed it all the way out (increases idle into the 3k rpm). Could I have assembled it back wrong? Any way to test it?

Hi Everyone, Up to date status: I checked for leaks using a smoke detector. I started by inserting smoke from the turbo intake side, held my throttle body open, and let the pressured (6psi) smoke fill my entire system. There were absolutely no leaks of any kind. I cranked the engine and set it to 15 degrees, then I started the engine and set it at 15 degrees (when cold it doesn't fluctuate), but when it warms up enough, it starts idling from 1,300 up to 2,500 RPM. I also noticed the timing moves with the idle. Maybe the timing isnt set and locked properly? How I set timing: 1. Unpluged TPS 2. Cranked engine without starting until CAS lines up with 15 degrees 3. Plugged TPS back in 4. Turned engine on (has high idle of 2,000rpm) 5. Adjusted timing offset on g4+ to read 15 on timing mark (still high idle) 6. Engine idle starts fluctuating and timing ranges from 10-25. Idle goes down as it approaches 10, idle goes up as it approches 25. I'm not sure how to stop the erradic timing or is it supposed to be that way? Or does that stem from another problem?

Hi all, I have a guy coming in tomorrow to do a smoke test. Through the research I did, a smoke test will find every leak imaginable if there is any. Hi Robbo, yes, I thought the target idle was WAY too high. Hopefully we can get the tune happy enough to drive it to a tune shop. It’s a different guy this time.

Adding a picture of the idle control valve for reference

Thank you! It was a little intimidating but I can officially rule TPS and timing out until the tune. A stable idle is what I’m looking for now. “Start ya bastard” is hilarious! I’ll give that a go tomorrow. I also torqued my intake manifold from Greddy to 14ft/lbs or 19Nm. A little over manufacturer spec since it’s an aftermarket intake. For the idle control valve, I took it apart and cleaned it. Maybe I didn’t assemble correctly? I would think the idle control valve either makes an idle lower or higher but doesn’t actually cause erratic RPMs. But I’m not sure. I will also be double checking connections tomorrow.

Hi Duncan and Robbo, Okay, I have done the following: 1. Calibrated TPS successfully, I noticed the throttle percentage was at 5% originally, but is now at 0% when closed and 100% when fully opened. 2. Set timing to 15 while cranking, turned the engine on, had to move -86 offset to -80 to read 15 across all RPM range, I would say timing now looks good! The car also seems to stay consistently at 180-190 degrees. Doesn’t seem to overheat anymore. 3. After setting TPS and timing, I did notice the idle start fluctuating from 1,300-2,300 RPM over and over. Like Duncan said, could be a vacuum leak. How do I locate vacuum leaks? Someone said to use a smoke machine, any other things to check? Seems like the issue now is erratic idle. Could intercooler leaks also cause the pulsating idle? Or a sensor, maybe the idle control valve? Anything to check on g4+? IMG_5685.MOV Thank you!