over the past month or so, since its become reasonably cool down here (50 degrees or so) ive noticed that after driving on the highway (70+ mph) or driving on long trips around town, my "in drive" idle seems to sit a bit higher - id say around 900.
if i throw the car in N or P, the idle jumps up and sits at an even 1500 rpms or so.

however this only seems to happen at night, when its pretty cold outside.

also, if i let it sit in P, idling at 1500 for a few minutes, it drops back down to its original, normal idle of 700-800.



my question is; what is causing this? is it the fact that ive run the coolant bypass when i did my NWP install, and the TB is not longer getting warmed by the engine?

what would cause an abnormally high idle for 10 or 15 minutes after a long/high speed trip?

 

hey wats up man thats absolutely normal i have a 96 max and after trios on the highway the temp needle goes fairly down and the car idles high for a lil bit after highway trips, the reason is like u said, u drive in the cold, the cold air constatntly coming in cool the engine, but the main point is its normal for it to do so

 

well it didnt seem to happen before i ran the coolant bypass (i.e. last winter)

 

that might be the reason i think but maybe other org'ers know better and can help u further i dont wanna guess at it

 

I think this temp actually skrews us all ROCKY.I had a thread like this not too long ago when FL was in the low 50's, i would start and it bogs down to like 200 and then jumps back up. Then on my way to skool i would be at stop lights and the car idling at 1500 and then it goes to 600 then back up then down, then up, then down.Pissed me off.

 

The only think I can think of is its due to the cool temperatures. Denser air, more bang.

If it fluctuates rapidly, then that is a symptom of a vacuum leak.

 

My LS 400 would occasionally idle as low as 400 PRM on hot days (A/C off, N or P). When its cooler it would idle at 700-800.

 

See if it does it when you don't have the heat on (fan).
Cars idle up when the heater is engaged. When you're driving, there is sufficeint rpm to bring the hot air in, when you stop (rpm lowers) the rpm will raise and fluctuate due to more load on the blower and heater core.

I'm not sure that this 'didn't happen to you last winter' it's quite possible you just didn't notice.

 

i never use the heat. ever.

i rarely use the AC.


and yea i notice the RPMS fluctuate when i hear the cooling fans turn on. im pretty sure its not that, but thanks anyway.

 

I think there is definitely some thing a miss. I get the same problem sometimes whether it's cold or hot and reguardless of accecories being on or off (which shouldn't make the car idle that high anyway). There is no way that without a malfunction that a warmed up car is going to idle at 1500rpm. If it were compensating for heat or something the rpm difference would be 200 at max. I have been unable to diagnose this problem on my own car so I can't be of much help right now. From a cold start it could idle that high. But 50 deg. Cold isn't cold at all just cold for florida(here it's like 30 or lower often). It's gotta be one of the many pia sensors this car is chock full of. But it's probably not fried enough to throw a code yet. Mine idles high mostly if I go somewhere and let the car sit for like 5 min and than start it up to leave the idle shoots up sometimes as high as 2k an won't come down unless I drive it ( I have a manual) so no gas just clutch and the idle will carry the car for a min an than go back to normal. I also noticed when I turn the car off while high idling it deisels a little(think I spelt that right).
Anyway good luck

 

mine goes up and down like 3 seconds between ups and downs.Where do you suggest i start scoping for the vacuum leak.?

 

finally! Someone else with the same problem as me. I have a high idle once the car is warm and it is cold outside. I also have run a coolant bypass. When it is warm out my car idles normal. This also has nothing to do with the water temp, it's only due to the outside temp. Are you willing to un do your coolant bypass to find out if that is the problem? I cut the coolant tubes off of my throttle body.

The only code I throw is an EGR code and that has happened ever since I did my 00VI. Let me know if you find out any thing.

 

YES, the high idle plunger is keeping your throttle body open. You can adjust it out so it never opens the TB and your idle should remain stable.

 

you have a eratic idle? when did that start happening?

if its even, it could be all kinds of things.
can you post up a vid?

though my car knowledge is still limited, my gut says that it is most likely the coolant bypass that is causing it. a) because it never happened last winter and b) that just makes sense - the 220 degree coolant is no longer warming the throttle body, and at high speeds, im sure the air gets near freezing as it enters the manifold.

que?

 

Get yourself a FSM or I think the Haynes shop manual has a good description of how the cold idle control works. That is definately your problem, look for cold idle plunger or fast idle cam in either book. It's down under the TB slightly off to the left You will see the linkage and the plunger. I believe the plunger goes in when the coolant temp is cold and pushes back out when it's hot. (might be opposite, I forget) That in turn opens the TB slightly for a cold start and closes it again once the coolant is warmed up. Follow the idle linkage, you'll see it.

 

I'll try my best to get a video....but what screws me up is it doesnt happen every time...which then makes things harder to diagnose.

 

I get that during those temperatures, and i don't have any mods in that area. I think a lot of maxis do that, and no one can figure out why.

 

heck yeah, i just bypassed my TB last week and i have the same problem as well!! mine idles at 2k sometimes, lol. imma have to look into the fsm pretty soon.

 

my car KIND of have this problem. but its happen almost everytime during the summer time. it happens after i have been driving for a while on city streets and out of no where it just starts to idle high. and if i put it on P, its at arounnd 1500rpms.
this is driving me nuts and i want to sell this thing now

 

why do you guys do this though.?....the bypass

 

whoa man slow down. no need to sell your maxima cuz the idle is too high.

basically the idea behind the coolant running through the TB is that in the winter time, the super hot coolant prevents the TB from collecting moisture and eventually icing up.

but down here in florida, that is a non issue, so it seems like a good idea - at least in theory.

plus its part of the NWP kit

 

well the thing is its been happening for a while and this problem is not the only reason i want to sell my i30. but i want a car with a manual transmission and 4 cylinder turbo i.e. evo, sti or wrx, audi, vw, saab

but anyway anyone have an idea about my problem? is it as same as the op?

 

need more information.

is the high idle static or does it change?

does it happen after doing a specific thing>?

 

well, my situation was different. i did it because i was working on an engine swap (yeah, that didnt turn out well), and i figured since my IM was bypassed from the NWP kit, i mite as well bypass the tb. i guess that doesnt work too well.
u know ur the second person that has told me this, but my NWP kit only came with instructions to bypass the IM and only one hose connector. maybe u bypassed the wrong thing?