gen3 3sgte bouncing idle

[hunging]

After alot of bs the gen3 has been dropped into my sw20. I cranked and there was a gen3 starting up.

The problem now is my idle is bouncing between 1500- 2000 rpm. The car revs fine up to 5000rpm but haven't tried anything higher. After revving it would just drop back down to 1500 and start bouncing again. Tried for 10 minutes and still the same thing.

It's late and I don't really know what info is relevant to this problem so please ask and I'll try to answer. Not sure where to begin.

One of the hoses was left off and plugged off with a screw. Not sure if its relevant. Excuse the poor phone camera quality:

[2jzhilux]

Check tps setting make sure idle contacts are closing on idle

Also check for air leaks

[Andrew162]

so you're saying that it's rev-hunting between 1500-2000rpm? seems a little high. I'm in for a vacuum-related issue. my 3S-GTE also had a bolt into a hose similar to that, IIRC it was jammed into a wastegate hose. not sure if that's relevant to you however.

[The Real Roadrunner]

id certainly be thinking air leak. the only one i can think of big enough is the vac signal for the brake booster on the drivers side of the engine.

id grab some wd40 and spray it on all connections to the inlet mani/head and see if the idle drops. if it does just do selected places to narrow down where the leak is.

cheers
linden

[hunging]

It's all a mess at the moment and I don't know if I should start with the electricals or vacuum leaks.

I was under the impression a vacuum leak would increase/decrease the idle, but not make it bounce. I've tried playing around with a few tiny vacuum hoses but that didn't do much and it just kept on hunting for idle. Just to confirm a big enough vacuum leak would make it hard for the engine to idle?

[Cuts]

yeh ive been here.
Yep vacuum leaks can make all the difference.
hard to make out specifically where that hose is (im used to a gtfour engine bay) That hose looks like the idle hose, goes to the throttle body, and the other end is supposed to go into your intake pipe.
Or could be one of the stock oil catch can hoses, either would cause issues.
like has been said check all vacuum hoses and plugs, even things like the dizzy plug.
failing those try cleaning the tps (throttle position sensor) and the isc (idle speed controller) even go so far as to take the throttle body off and clean out all the shit thats most likely in there. While your at it disconnect the coolant lines from the tb, not needed im TAS weather let alone NSW lol.

I like silicone spray for cleaning terminals or that c20 spray sparkies use.

Reset ecu after you have done all of this too.

Another thing, mine used to do this after i had reset the ecu or been altogther disconected for a while, i put it down to the ecu re learning (as they do), after a couple of minutes of driving it returned to normal.

[Andrew162]

that's what that hose could be as well, looks like an ISC hose... is there anywhere that's unplugged or capped which would fit this hose? if so, plug it in and see what it does.

[mikie_121]

From what you have described I think had the exact same problem with my car. Although it's only a 162, 3sge. My car would idle up to 2k rpm, and after about 2 mins it would start hunting between 1500 to 2000rpm.
My problem stemmed from the throttle body not getting hot water. At the bottom of the throttle body there is a wax valve that expands as the water in the engine gets hot. The expanding wax valve closes a bypass air hose that lets air past the throttle plate. When the computer detects that the idle speed does not slow down after a preset time then the computer starts revving the engine, maybe to try and pump water through the throttle body. In my case this made it overheat while sitting at the lights (due to a partially blocked radiator) and the pressure finally blew out the seal around the water pump.
I solved the problem with another throttle body from the wreckers and a new water pump gasket.

I hope this helps and I hope nothing blows out for you.
Mike

[hunging]

Here's another pic of the plugged hose:



Think it would be wise to double check the wiring first before troubleshooting.

[Cuts]

yeh that wireing looks a lil odd :S.

I notice the stock catch can isnt on? is it usually?

Ide say its either the idle breather tube like i stated earlier or the lower oil catch can hose.

[hunging]

yeh that wireing looks a lil odd :S.

I notice the stock catch can isnt on? is it usually?

Ide say its either the idle breather tube like i stated earlier or the lower oil catch can hose.

lol yeah it does look a bit ghetto. Repinned the existing gen2 turbo harness and added wires where necessary.

The catch can didn't come with the engine.

Thanks for narrowing it down.

[Cuts]

I have one of said stock catchs can if you would like it

[hunging]

From what you have described I think had the exact same problem with my car. Although it's only a 162, 3sge. My car would idle up to 2k rpm, and after about 2 mins it would start hunting between 1500 to 2000rpm.
My problem stemmed from the throttle body not getting hot water. At the bottom of the throttle body there is a wax valve that expands as the water in the engine gets hot. The expanding wax valve closes a bypass air hose that lets air past the throttle plate. When the computer detects that the idle speed does not slow down after a preset time then the computer starts revving the engine, maybe to try and pump water through the throttle body. In my case this made it overheat while sitting at the lights (due to a partially blocked radiator) and the pressure finally blew out the seal around the water pump.
I solved the problem with another throttle body from the wreckers and a new water pump gasket.

I hope this helps and I hope nothing blows out for you.
Mike

Correct me if I'm wrong but from what I've read on the net the 3sgte gen2 onwards don't use the wax isc.

I've unplugged the ISC and still the same thing.

[mikie_121]

what part did you unplug?
There are no electronics in the wax mechanism (in mine at least). If you can squash (or block) the hose that bypasses the throttle body that should give you a definitive answer whether that is the problem. If it still runs wierd then ignore my solution

Mike

pardon my ignorance, but what does isc stand for?

[LeeRoy]

Does the 3s have a high idle when cold like that of the 4age. If so, my 4age had done this perviously when the coolant was low as it gives hot/cold/hot/cold readings from coolant splashing on it. The engine adjusts rpm to suit resulting in an idle that hunts.