Thread: Anyone else had ongoing issues with hunting idle?

Ive had a lot of issues over the time ive been using tunercode/nismotronic/nemu, with the idle hunting sometimes. Its inconsistent, sometimes the car drives and idles perfectly, but other times the idle will hunt badly, which is quite embarassing.

Ive tried a lot of things, adding fuel into the lower part of the map, as when its doing it the revs will rise, mixture will richen, then revs drop and it leans, then seems to try compensate and revs up again. Im assuming its the idle control valve trying to settle the rpm, but no matter what i do with idle timing and base idle duty i just cant make this issue go away 100%.

I can go out for an hour, starting stopping to try make the problem happen, and it will not do it once, then it will do it, often as arriving at someones house and they are like "dude, what the hell is wrong with your car?".

I dont know if its related to fuel cut, idle duty on idle control valve, map values? I dunno, ive changed a lot of stuff over the time, and often end up with a car that drives like a complete pig and have to revert back to a old tune.

so hi idle when backing off/ coming to a stop? but not all the time?

No not all the time.

It sometimes happens on startup, just turn the key and it will start by itself, but then rev too high and then drop and then just keeps doing this for maybe 15 or 20 seconds. Otherwise it tends to do it when trying to move slowly, like backing out of a driveway when riding the clutch a little, which makes it very hard to keep constant rpm to move the car slowly. Trying to drive out of it with thottle usually makes the car buck and shudder and drive terrible, so need to just wait for it to finish the cycle, then it will drive fine and not do it again straight away. This makes it very hard to log and work out what is going on.

I also think there is a slight lag in the AFR display due to the sensor being outside of the engine, so just because its saying lean or rich, you cant tell exactly if its leaning because rpm is dropping or because its going lean as rpm drops which causes it to overcompensate and climb too high again.

i only have 1 idea, from my own experience. i know your really clue'y with the tuning side of things, but maybe it might be worth a quick look at the mechanical side of things. i still have a high return idle, which sometimes take's a while to settle. it makes the car hard to brake and sometimes it bunny-hops a bit, which i can feel through the engine mounts, and it gives me the shits. its not all the time, but enough.

i'd had advise that the tune need adjusting, that it's a bit rich or the k-constant's a bit out. i'd changed stuff, i've reset the ecu, i've cleaned the aicv and maf, i've used throttle body cleaner,still it's there.

several times i've been sitting at the lights, and it's like 1500rpm trying to go down, and i've nearly stalled it 1/2 opening the clutch in first while being braked, and the idle has came back down to where it should be, then it dawned on me...what about the throttle cable? so i drown the cable in wd40 at either end....and the problem goes away.

anyway that's me, its probably not you, but check your cable and throttle body. might be worth it.

I had an idle hunting problem last year, once I put in new injectors I was golden. The old injectors were just that old and dirty.

After driving for about 2 hours today with laptop recording logs, the problem didnt show its head once, until i turned the laptop off, then it went nuts. I had to put it in gear and ride clutch out to load it up to get it to settle in the end.

Hopefully internal logging will be added back into SA at some stage.

That sounds an awful lot like a grounding issue.

Dave

Hm. Ok..... Hangon, been having low voltage issues too, related to failing alternator, or low voltage due to bad earth....

I did check the main earth strap the other day when i noticed low batt voltage, its a big aftermarket one, but wondering if i need to give all the earths a good check and add an extra one. Battery is in boot (trunk) too, so might need to give it a good going over....

Havent been able to find any earth faults so far, everything is tight and clean, multimeter is showing no resistance.

Im still inclined to think its something in the tune as ive had another car do this and havent been able to resolve. Sometimes its totally fine, but then plays up. I know it often does it when i leave my exwifes driveway, so will try log it when i go there soon, been trying to get a video too so you can see how horrible it is. Ive also got a N1 intake, so the big TB does make it a little tricky to move off, so when its doing the idle ocillations its impossible to hold constant rpm to move off slowly.

It does seem like a idle control issue. Ive got timing idle control active, as its considerably worse if i turn it off. Does using timing idle control stop the AAC valve from being as active? It seems to stop the AAC duty when i looked once.

Could be a leaky TB. Check the shaft bearings for wobble/wear.



I don't think it's an idle control issue because it's not consistent.

Using timing idle control does not stop AAC valve idle control.

Dave