mike2016 Posted June 13, 2021 Report Share Posted June 13, 2021 when the AC is on, and during throttle off, such as coming to a stop. Idle drops to 600-700 RPM then climbs back up. It never stalled. my idle target is 950 RPM. it's perfect with NO AC. I set AC Idle up at 100RPM and AC Offset table to 10 Integral gain is 2.5 Quote Link to comment Share on other sites More sharing options...
essb00 Posted June 14, 2021 Report Share Posted June 14, 2021 What type of idle actuator and idle mode (closed/open loop?)? Try adding Dashpot Offset (plus hold time & decay time)... Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 14, 2021 Author Report Share Posted June 14, 2021 Closed loop. RB26 oem actuator. Dashpot is 0. didn’t notice this issue until today also start up when hot also starts at very low rpm for some reason. Idle position is stuck low. I’ll attach a log later here’s the tune file https://www.dropbox.com/s/2guzof23h6uspyo/13 - Ignition table update.pclx?dl=0 Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 14, 2021 Author Report Share Posted June 14, 2021 Here's a log of the start up. ECT was over 90C. https://www.dropbox.com/s/8vr9amu85376p9i/PC Datalog - 2021-06-13 5%3B10%3B10 pm low idle after start up hot.llgx?dl=0 it starts up and idle drops to 600-700 when "start up decay" starts. never noticed this problem before maybe it has to do with the AC low idle slow recovery issue Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 14, 2021 Report Share Posted June 14, 2021 In the log your engine needs 58% DC on the idle valve for the target idle speed and timing to be met, yet your idle base position only has 10% in it. So either the base position table has been changed at some stage, or the throttle is more closed that in used to be or similar. Have you got any old logs that show if the enegine has always needed 58%DC to idle when warm? Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 14, 2021 Author Report Share Posted June 14, 2021 i'll try to dig up some old logs. I remember i set the idle base position at 10% because that's what in the parameter list when I observed it. Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 14, 2021 Author Report Share Posted June 14, 2021 And why is idle low when it’s in “start up decay” and recovers when it’s in idle mode? It definitely didn’t have this problem before Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 14, 2021 Report Share Posted June 14, 2021 7 minutes ago, mike2016 said: And why is idle low when it’s in “start up decay” and recovers when it’s in idle mode? It definitely didn’t have this problem before Because you have 10% in your base table and 20% start up step, so it starts with the valve at 30% and as the 20% startup step decays it falls all the way back to 10% - but remember from above your engine actually needs 58% for the correct RPM, so this is why the idle is low. After the startup step has decayed then closed loop turns on and the ECU winds the valve open untill the correct RPM is reached. Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 14, 2021 Author Report Share Posted June 14, 2021 I looked at the log again. a bit after the 0:08 mark, idle position is still at 30%, and RPM is already dropping. start up decay doesn't start until 0:12. i found some old logs at the end of the log, it's idling at 10% https://www.dropbox.com/s/hsc4waqreo6c3m3/PC Datalog - 2021-03-21 12%3B42%3B19 pm static run 2.llgx?dl=0 some street driving, also at 10% https://www.dropbox.com/s/k5tv00f4z73ypuu/PC Datalog - 2021-04-24 5%3B18%3B50 pm.llgx?dl=0 this is a cold start log https://www.dropbox.com/s/wf9n1txiq07w810/PC Datalog - 2021-05-23 4%3B19%3B42 pm.llgx?dl=0 there's no hardware change on the car recently. only thing I did was the boost control valve, and a clutch fan change (a bit of coolant lost from upper radiator hose disconnect, but refilled after) Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 14, 2021 Author Report Share Posted June 14, 2021 changing idle setting to default Link base map setting. will test soon. Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 14, 2021 Report Share Posted June 14, 2021 2 hours ago, mike2016 said: a bit after the 0:08 mark, idle position is still at 30%, and RPM is already dropping. start up decay doesn't start until 0:12. That is where the AC clutch turns on. I assume there is a startup lock out or similar so it is not on when cranking. If old logs show the idle valve at 10% to acheive the same RPM that now needs 58% then it suggests air flow through one part of the sytem has changed somewhere. It could be the throttle was not fully closing before or something similar. I also note in your older logs that the idle valve and idle ignition are both pinned against the minimum clamps so something has quite drastically changed. 1 hour ago, mike2016 said: changing idle setting to default Link base map setting. will test soon. Thats not what it needs, most of your settings look ok, just the base position table is now a mile off for whatever reason. Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 14, 2021 Author Report Share Posted June 14, 2021 maybe a bad idle valve that was stuck and now it somehow "fixed" itself? the throttle are new OEM RB26 ITBs. there's absolutely no change on the car that would affect airflow.... Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 15, 2021 Author Report Share Posted June 15, 2021 Here's another log from today. Idle valve is at 10% at 50C and up ECT.... does Idle valve duty change drastically when ECT is higher?? doesn't make any sense. https://www.dropbox.com/s/z5xzk2iztigb5p0/PC Datalog - 2021-06-14 7%3B15%3B19 pm.llgx?dl=0 Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 15, 2021 Report Share Posted June 15, 2021 Yeah so it seems you have a some investigation to do, either the idle vale is playing up/sticky, the throttles sometimes are closing fully, or there is extra air getting in from somewhere else. Split hose, PCV, brake booster, etc. Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 15, 2021 Author Report Share Posted June 15, 2021 if its a split hose or air leak somewhere, it should always leak somehow regardless of temp? this low idle issue is new, the car gets hot like this every time i drive. never had this issue before. i'm going to focus on the idle valve and do some investigation. all the hoses are new OEM, and i just worked on the car over the weekend, if there's anything off visually i would've caught it... what does the idle valve screw have in relation to the DC% in the ECU? Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 15, 2021 Report Share Posted June 15, 2021 41 minutes ago, mike2016 said: it should always leak somehow regardless of temp? What makes you think it is related to temp? You have logs above which show either 10%DC or 58% DC to achieve the same idle speed at the same temperature (hot). So temperature doesnt seem to be a factor. 46 minutes ago, mike2016 said: what does the idle valve screw have in relation to the DC% in the ECU? I've never adjusted one but they are usually just a bypass adjustment. Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 15, 2021 Author Report Share Posted June 15, 2021 2 minutes ago, Adamw said: What makes you think it is related to temp? You have logs above which show either 10%DC or 58% DC to achieve the same idle speed at the same temperature (hot). So temperature doesnt seem to be a factor. I've never adjusted one but they are usually just a bypass adjustment. yea that's what i meant to say, if there's a leak, it should be leaking somehow, regardless what temp the engine is at. so it's not temp related. and if there's an apparent leak, it's pretty noticeable to the ears, which I don't notice any. i think i can rule out the leak for now and just focus on the TB and idle valve. I'll try to play with the adjustment screw and see how it affects the idle base position. i think 10% DC is quite a bit lower than usual? the previous shop had the idle setting on open loop and probably messed with the adjustment screw to set the idle. Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 15, 2021 Report Share Posted June 15, 2021 Yes 10% is low but 58% when hot is high. So its unlikely the screw, it is something that is changing intermitantly. And no, you dont hear all leaks, PCV valve and brake boost are common examples - you can clamp off the hoses when you have low idle DC reported to rule out those. You can also clamp off the hose on the idle valve when the idle DC is low to rule out if there is a lot of air flowing through that. Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 16, 2021 Author Report Share Posted June 16, 2021 haven't had a chance to investigate the hardware yet but... https://www.dropbox.com/s/z5xzk2iztigb5p0/PC Datalog - 2021-06-14 7%3B15%3B19 pm.llgx?dl=0 from this log. it seems like the "idle valve" is offset by the idle ignition ? (idle valve at 10% but idle ignition increased to bring idle rpm up to target) does either idle ignition or idle valve have priority as who controls the idle first before the other ? Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 16, 2021 Report Share Posted June 16, 2021 Ignition is the proportional & derivative, valve is the integral. So in other words ignition is the instantaneous correction for error, valve is to correct long term error. The main reason your idle valve is moving in large steps is it looks like you have a large deadband set - about 100RPM at a guess. So idle valve doesnt attempt to move until idle speed is 100RPM off target. 20 or 30RPM would be a more typical deadband for a solenoid. Quote Link to comment Share on other sites More sharing options...
mike2016 Posted June 19, 2021 Author Report Share Posted June 19, 2021 I wasn't able to replicate the same issue i did however try to clamp off different air hoses and found no difference in idle. another thing i can think of is the "air regulator" - i'm not sure if it's even connected. as the previous shop who did my car bypassed the FP speed module, not sure if they took out the air regulator circuit with it. my fuel pump is powered by just the fuel pump relay AUX 6 now. i'll have to verify if there's power at the air regulator. AUX 1 is unused, and AUX 2 is used for VVT solenoid the air regulator is like a mechanical thermostat ?... big change in air temp / engine temp will probably cause it to somehow change its position if it's not powered? Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 20, 2021 Report Share Posted June 20, 2021 Ah yes, forgot they had those. Its basically a valve powered with a bimetalic strip that bends when it heats up. So when the engine is cold and the strip is cold the valve should be open to allow a bit of extra air through. With ign on, a heater heats up the strip and should close the valve (engine heat should keep it closed for hot restarts etc too). I havent had much to do with the nissan ones, but certainly the similar device used in older BMW's are not very reliable so it could well be causing the intermitant change you are seeing. Quote Link to comment Share on other sites More sharing options...
VegasAWD Posted August 19, 2021 Report Share Posted August 19, 2021 On 6/13/2021 at 10:52 PM, Adamw said: In the log your engine needs 58% DC on the idle valve for the target idle speed and timing to be met, yet your idle base position only has 10% in it. So either the base position table has been changed at some stage, or the throttle is more closed that in used to be or similar. Have you got any old logs that show if the enegine has always needed 58%DC to idle when warm? Hi Adam, is there a formula that determines how much dc or how many steps the ecu needs to hit a target rpm? I thought you just kind of trial and errored it? Quote Link to comment Share on other sites More sharing options...
Adamw Posted August 19, 2021 Report Share Posted August 19, 2021 No, but in the case you are quoting from above, the user had closed loop enabled so you could see in the log the ecu was moving the valve to what was required to achieve the idle speed, which is where the 58% came from. Quote Link to comment Share on other sites More sharing options...
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