Little issue at idle..
 

Hi guys,

Just wanted to post this thing that's been happening for a little while and not really sure what could it be...

I have a 6MT w/sport package 370Z.. I have bolt-on mods like Stillen CBE, Berk HFCs, Stillen Gen3 Intakes, Stillen standard pulley...

The thing is, I've noticed that when I'm driving around, as soon as I stop, for example at a red light, and the car is idling, engine RPMs are steady usually at 750rpm, but for a fraction of a second they drop a little below 500rpm giving the feeling that the car is going to shutdown, and then the RPMs raise back up to normal idling... I can drive around for a while and whenever I stop it will happen again...

Any ideas on what may be causing this..?? Could this be a leak on the intakes or exhaust..??

I'll try to get it on video and post it up..

Any help appreciated...

Bad o2 sensor maybe? I dunno. I had that problem with my RSX too and it had a bad o2 sensor. I never fixed it. Traded it in and got the Nismo instead.

I notice it sometimes with my car as well. It's not frequent and I can't replicate it. Essentially as you described, it sometimes 'stutters' on the idle for a moment when coming to a stop. Fortunately, it's never died and doesn't do it often so I've ignored it. i don't think it's intake or exhaust related (I have stock intakes except for the COBB tubes, and it did it before the COBBs).

I'd guarantee your dealer would just shrug if you brought it in and told them about it. Or they'd try to make you pay for a $150 fuel injector cleaning. I think we have to wait until it's either frequently happening or keeps the engine from starting (hope it never comes to either of these).

I was just about to post about this same exact issue. my Car is completely stock and dips revs @ 500 or lower when I i stop. I have some Berk HFC's waiting to be installed but want to sort this out first.

is the AC on? Could it be the compressor clutch engaging and disengaging? Or maybe the radiator fan coming on and temporarily taking more electricity from the battery and weakening the ignition? Or maybe it's the electronic throttling system on the car, which does tend to be a bit sluggish and slow to respond.

Yeah, sometimes the AC can cause some hiccups in the engine's idle speed.

Cannot be the A/C compressor cutting in,because our engine is a 3.7v6[good torque in idling],not a 1L in line 4.

Not so sure about that reasoning. Our AC compressor really pulls on the motor. On a hot day, my idle will go from ~700 without AC up to about 900rpm with the AC running. Catch the Z off guard (if you will) and you go from 700rpm to 500rpm...a perceived hiccup.

That being said, I've had the low idle hiccup on hot days with the windows down and AC off.

It happens whether the A/C is on or off.. The effect is less noticeable with the A/C off but it still happens...

Anyway,when we modify the car,we expects the car idling to change,the best is stock if you want the best idling,i remember my friend's Subaru STI,he changes his cams,results is an engine as rough as a diesel at idle.!

see i have that problem too and when my ac is off it goes to 500 but when i turn it on it immediately revs itself back up.

I have to disagree with that. The A/C compressor IS a significant "drag" on the engine when the clutch engages it. It will affect the idle speed momentarily.

Mine does this as well sometimes as well as the Max......Never had any major issues as a result.

Was watching the tach but mine is solid at 700rpm or so. Even with AC running it doesn't affect too much. Temp 65F.

Mines steady as a rock ac or no ac. But I have the 7AT.... could it be the rev match on the 6mt possibly glitching?

Not that as mine does it from time to time and its a 7spd auto.

Not sure but mine is 6mt.

I just noticed something on the car i noticed on a lot of other cars as well. Are you putting any pressure on the steering wheel when the rpm falls? It's a common incident in all cars with power steering. If you touch the steering wheel and put some torque on it, the power steering pump engages and applies fluid pressure. This increases drag and drops rpm down a bit for a couple of seconds before the ecu compensates by increasing the throttle opening and regaining normal idle speed.

My G35 did this every time I swapped intake manifolds or installed a plenum spacer.. Did exactly what you described. It would eventually go away after a day or two. I believe it was the ECU learning the new mod I had installed.

Could this be a factor for your car and it's mods?

EDIT: Just for reference I've went through 2 plenum spacers, and 3 different intake manifolds.

*** Update ***

added a techron bottle to my gas fill-up and the low rev dips are not a noticeable issue as of now, Seems my fuel system was kinda dirty, I will observe and probably do an techron bottle with every oil change from now on. I used to do this regularly on my old car but tough maybe I was exaggerating.... guess not.

Noticed this with my car tonight (2010 nismo) whenever I'm in a stoplight it dips below 1000 or around 500. AC was running on lowest settings. Should I contact dealer or not?

I had the same issue as the OP. The problems went away after cleaning the throttle bodies, and then performing the Idle Air Volume Learning procedure. After that, my idle rpm is steady at roughly 700. Hope this helps!

550rpm in normal for our engine.

I got that, too, when stock. With turbos and larger fuel pump, I can hear the fuel pump power sag for a little bit when it happens. Not sure if it is related.

good to know, thanks! :tiphat:

Reviving this post as I happen to experience the same problem. I haven't really noticed if related to A/C but I definitely have some, apparently random, idle dips of ~500rpm. What worries me is that a couple of times (one of which a week ago), the RPMs dropped like the engine was about to die and then revved back up to normal idle. I will keep an eye if this happens also with A/C off.

Stillen Gen3 CAI <= could be this. or a dirty MAF

was it doing it before your flash?

I don't recall it being a problem before the flash. Definitely not the RPM dip to 0. In fact I was thinking it could have been related to the tune.
Thanks for the tip, I will try to inspect the MAFs to see if I see anything wrong with those for now.

yah, if your maf is clean and if you can flash it back to oem for the time being just to see if it comes back or not, that would be a good start.

i donno, can you take a log and maybe send your file to uprev and see if they can pinpoint it on the map?

Yup. I can log. Good point I will try to monitor that, log and eventually send to UpRev. :tiphat:

mine does it too. i got Berk HFCs and Stillen G3.

It did it when i had my AEM intake too but not as much as with the Stillen.

I think it's got something to do with the CCV pipe barb on the Stillen tubes being narrower than the stock one. The AEM barbs are a little larger in diameter.

When i had just the HFCs, i dont think i can recall it happening.
i have done several versions of the throttle body idle relearn procedure, and the frequency of the idle dip has reduced a bit. The motor does seem harder to feather when reversing for example - ie it feels like it's easier to stall.

Yeah I believe it could be the G3's. I caught the engine dropping RPMs with the A/C off too so it's not that. Still need to check the MAF.

yesterday i dug out the stock accordion pipes and measured the ccv fittings.

RHS (US passenger side) had a 16mm opening to accept the ccv resonator barb, with a restrictor cast into the bottom of it nearest the fresh air stream. approximate diameter at this restriction is roughly 13mm (couldnt get caliper in there to measure without destroying the accordion pipe.
The inner diameter of the ccv resonator barb is roughly 13mm

LHS (US driver's side) has a helmholtz style resonator mated to a 16mm opening.
This accordion pipe also has a 16mm opening to accept the ccv resonator barb. There is no restrictor on this side, it's 16mm straight thru. Inner diameter of this side's ccv resonator barb is also roughly 13mm.

Now, the Stillen G3 features 12.5mm barbs on both sides.
AEM has 13mm on both sides.

I cut off the barb on the LHS and tig welded on a 15.5mm ID bung. So far it's been alright. I did a idle relearn last night and the idle dip seems to happen more now, but i've been told it needs time to learn and it will improve.

Will report back when something interesting happens.

I have the same issue on occasion, and had the same issue on my G35 sedan which was the reason I sold it. It started out with the dip in idle then progressed to almost completing stalling then would stall. I could never replicate it for the dealer. Not a month after I sold it the technician that tried his hardest to find the problem called me and said Nissan had finally issued a tsb for it. So long ago I can't remember but I can dig up the tsb he emailed me if you want. Cost was $2k in parts alone, something about cams and magnets not sticking when oil temp is warm.

Mine does this only when I have the AC on and I'm stuck in traffic(LA style traffic to be specific) heat soaked like a mofo but once I'm cooled down it stops doing it.

Maybe the same thing is happening to you?

Might be onto something there. (AC was off for me)

I was just stuck in traffic a good 30min. Once I got up to my red light, RPM's started to be a bit fishy, 500 or so teetering on the feeling it was going to stall.

This is a 2013, 6 months old. Never had it in traffic yet this long, bout low 80's for ambient temps.

No hesitation once the light turned green, got it to the driveway, seems to be fine.

Will see whats good tomorrow on the way to work.

Also considered maybe low fuel, but still have 4 dots, no warning lights. I usually fill her up at 3 dots, so tomorrow is the day anyways.

Approx 4,500 miles on the ticker, I wouldn't think there should be any issues this early!

i think its just heatsoak, cause when i was experiencing this, i had well over half a tank of gas, and san diego traffic is never as bad as LA traffic and it was one of the first times i was stuck in legit no one is moving traffic for a couple hours

iirc it was 85 out that day

I've also had the same issue for a while - rpm dip while idling, and I also had another issue once - when I started my car warm, the car didn't catch its idle after starting, and died immediately. I'm thinking it may be spark related? Gonna check those this coming week.

Some of us are getting the hot start issues as well, and mine's probably the GTM tune. I just give it a little gas on startup, and it fires up just fine.

My car is stock and it drops low while idle too.. It's not the mods, it's something else that's cauing it. Fan/AC have no effect on it either...