Rb26 Hunting

[Sciclone]

Hi All...

My GTR is hunting at idle. It happens after the car reaches ~82 degs. I'm guessing it's got something to do with the thermostat opening causing something to leak vacuum, but I'm not sure. It's really driving me bonkers. Has anyone had this problem, or have any idea what could be causing it.. I don't want to just start replacing random bits, but I don't know what it is.

[DVS JEZ]

Have u changed anything recently?

What rpm does it idle at before it starts to hunt?

What ecu?

[wolverine]

Have a good look for a vacuum leak, especially at the front of the plenum. I have seen several cars with with a small split on the bottom that open up when the rubber softens but is hard to spot.

[djr81]

Hi All...

My GTR is hunting at idle. It happens after the car reaches ~82 degs. I'm guessing it's got something to do with the thermostat opening causing something to leak vacuum, but I'm not sure. It's really driving me bonkers. Has anyone had this problem, or have any idea what could be causing it.. I don't want to just start replacing random bits, but I don't know what it is.

Why not adjust the valve that controls how much air the motor gets at idle?

It is under the plenum. Just screw it in & see if your problem goes away.

[Sciclone]

DVS: its running a powerfc. Nothing has been changed on it recently and it's been doing it for a while. Thats why I thought vacuum or mechanical component. I've tried changing the 02 sensors, and resoldering the afms but to no avail.

DJR: adjusting the aac won't stop it hunting if there is a vacuum leak or what not.

[DVS JEZ]

U need to do a thorough check for leaks, get a smoke test done, and make sure the car is hunting before u test it(82degrees)

Might even be something in the power fc when it reaches 82 degrees idle control or enrichment etc might need a tweak.

[djr81]

DVS: its running a powerfc. Nothing has been changed on it recently and it's been doing it for a while. Thats why I thought vacuum or mechanical component. I've tried changing the 02 sensors, and resoldering the afms but to no avail.

DJR: adjusting the aac won't stop it hunting if there is a vacuum leak or what not.

No, it wont. But given it takes 30 seconds to check & that it is probably the cause I reckon it is a good place to start.

[Sciclone]

It just seems weird that it wasn't doing it when I first had the PFC installed. I'm not happy with the tune anyway, but I'd like to have it not hunting when I go to get it tuned.

Would the pcv valve be a possible cause (heat causing the spring to go sloppy)? Otherwise, I might just get a length of vacuum tubing and redo all the vacuum hoses and see if that helps.

[djr81]

First rule in fixing cars. Check for obvious/easy stuff before rebuilding the thing from ground up.

[EAT26]

Hi All...

My GTR is hunting at idle. It happens after the car reaches ~82 degs. I'm guessing it's got something to do with the thermostat opening causing something to leak vacuum, but I'm not sure. It's really driving me bonkers. Has anyone had this problem, or have any idea what could be causing it.. I don't want to just start replacing random bits, but I don't know what it is.

Why not adjust the valve that controls how much air the motor gets at idle?

It is under the plenum. Just screw it in & see if your problem goes away.

This I feel is the answer to all your worries.

DVS: its running a powerfc. Nothing has been changed on it recently and it's been doing it for a while. Thats why I thought vacuum or mechanical component. I've tried changing the 02 sensors, and resoldering the afms but to no avail.

DJR: adjusting the aac won't stop it hunting if there is a vacuum leak or what not.

No, it wont. But given it takes 30 seconds to check & that it is probably the cause I reckon it is a good place to start.

+1

I had the same issue fixed by adjusting the idle control and also failing that cleaning AAC valve I got suggested by a member on here and it resolved my issue.

[Sciclone]

Thanks for your input Eat26.. I cleaned out the AAC recently (pulled it all apart and gave it a good scrubbing), but it was doing this before and after..

I will try adjusting like you and DJR suggested, and let you know how I go...

[DVS JEZ]

Check all the throttle linkages too. One might be open more than the others

[MrStabby]

First rule in fixing cars. Check for obvious/easy stuff before rebuilding the thing from ground up.

Dammit i've got to sig that. So few words, so much sense.

[wolverine]

Have you thoroughly checked the vacuum lines yet?

[EAT26]

Thanks for your input Eat26.. I cleaned out the AAC recently (pulled it all apart and gave it a good scrubbing), but it was doing this before and after..

I will try adjusting like you and DJR suggested, and let you know how I go...

It could also be build up on the throttle bodies.

I got this spray stuff lol. cant remember off the top of my head spray it into the plenum, and some vac lines to clean it out.

http://www.skylinesaustralia.com/forums/topic/110431-diy-aac-valve-cleaning-idle-reset/

have you cleaned the AFM's as well?