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Idle hanging for a moment, why? 

 

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 Post subject: Idle hanging for a moment, why?
Posted: Thu Jun 21, 2012 6:44 pm 
Stock as a Rock
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Posts: 165

Joined: 3rd Sep 2008

Ride: XH

Location: . .
NT, Australia

I've put a few questions up here while I've been putting the BBM into my XH. It's running well and got no dramas except for a hanging idle. When I back off the throttle, it falls slowly, hangs at about 1200-1500rpm for about 5 secs, then falls back to 800 or so. I disconnect the ISC, it falls back to idle fine, it just doesn't like it when I have the AC on at idle. I drove around with the ISC disconnected and it drove better but was about to stall at idle.

- The throttle butterfly is not sticking
- The ISC seems to be working because I disconnect it, it falls to base idle and RPMs drop when I turn the AC on.
- ISC resistance is 9.8 (ok)
- ISC gasket is good (new)
- PCV is connected to the pipe under the throttle body on the BBM
- Rear rocker cover vent is connected to the pipe at the throttle body
- The pipe connector on the intake before the throttle body is blanked off
- I cannot find any vacuum leaks
- Everything was working fine before when I had the log manifold

If anyone has any ideas it would be great. It took me a while to get the BBM in and this last bit is getting annoying.
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 Post subject: Re: Idle hanging for a moment, why?
Posted: Thu Jun 21, 2012 7:01 pm 
Technical Contributor
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Age: 28

Posts: 3705

Joined: 27th Sep 2006

Gallery: 20 images

Ride: ED Falcon

Power: 133 rwkw

Location: Leeton
NSW, Australia

Hi,

If you read my build when I installed the BBM on my car... I had the same issue... I replaced the IAC in the end and made it better... Details can be found in my build in my sig below...

Cheers,
Tim

 

_________________

93 Red ED 5spd Manual Build Thread

Performance: Complete AUII VCT Wiring & Power Train, Pacey Headers, 2.5" Exhaust, Exedy Clutch, DBA Rotors
Visuals: FG XR Wheel, XR Front, 17's, BA 5 Spd Shifter, BA Ghia Window Switches, NL Cluster
Tunes: 8" Pioneer Sub, JBL Speakers, Clarion Double DIN Headunit

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 Post subject: Re: Idle hanging for a moment, why?
Posted: Thu Jun 21, 2012 7:52 pm 
Stock as a Rock
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Posts: 165

Joined: 3rd Sep 2008

Ride: XH

Location: . .
NT, Australia

Yeah I've had a look at your build thread from time to time, so much work and so much info! I read it some more and think you have the AU throttle body with the AU IAC/ISC. Am I right in reading that you replaced the IAC with a second hand AU one and it fixed the problems?

I put my XH IAC on the EF/EL throttle body that came with the BBM. I'm pretty sure the XH IAC is the same as the one that came with the BBM (but it was pretty dirty). The parts numbers stamped on the plate match.

If I can try another IAC it could help, but none of my mates here have E series. I'll see what I can find.

If the ECU doesn't settle down and help the idle, I might put a switch in like I think BenJ did. I tried some gaskets with different sized holes (I used an eyelet kit to punch some varying diameter holes) and it didn't seem to make much difference.
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 Post subject: Re: Idle hanging for a moment, why?
Posted: Thu Jun 21, 2012 8:17 pm 
Technical Contributor
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Age: 28

Posts: 3705

Joined: 27th Sep 2006

Gallery: 20 images

Ride: ED Falcon

Power: 133 rwkw

Location: Leeton
NSW, Australia

Ah cheers...

Yeah first I fitted an EF IAC which came on my EF BBM top section... That fixed the hang... But I didn't want to cut the AU plug off and attach an EF one as the plugs were crappy on the EF so I chased up another AU IAC and that made a different... Could try spraying a head of carby cleaner up it and then blowing it out... Whether they get get sticky or what I don't know...

Mine will rev hang on occasion and doesn't decay in revs during a gear change as fast as i'd like when hot... But all in all isn't too bad to drive... Ideally on a "go fast car" you'd piss it off and set a base idle which it runs at and use that... For a daily it is well suited, when functioning properly of course...

Cheers,
Tim

 

_________________

93 Red ED 5spd Manual Build Thread

Performance: Complete AUII VCT Wiring & Power Train, Pacey Headers, 2.5" Exhaust, Exedy Clutch, DBA Rotors
Visuals: FG XR Wheel, XR Front, 17's, BA 5 Spd Shifter, BA Ghia Window Switches, NL Cluster
Tunes: 8" Pioneer Sub, JBL Speakers, Clarion Double DIN Headunit

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 Post subject: Re: Idle hanging for a moment, why?
Posted: Thu Jun 21, 2012 8:41 pm 
Stock as a Rock
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Posts: 165

Joined: 3rd Sep 2008

Ride: XH

Location: . .
NT, Australia

Tried the carby cleaner, it seems clean inside but I wondered if the little valve wasn't seating properly.

I'll run it as it is for a while, try another IAC if I can find one reasonably priced, otherwise I think the switch might be the go. I might keep the IAC for carparks and warming up and feeling lazy etc, flick it off when I'm on the highway or windy roads.

It's just a bit annoying that I made progress with a better manifold but went backwards on the idle side of things. Not a huge drama though.

Thanks for the replies.
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 Post subject: Re: Idle hanging for a moment, why?
Posted: Mon Jun 25, 2012 1:10 pm 
Getting Side Ways
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Age: 26

Posts: 789

Joined: 9th Dec 2011

Ride: S1 eb 5speed

Location: Coffs Harbour
NSW, Australia

Mine did this when the accelerator cable was binding up, when its hanging again try lifting up the accelerator pedal.
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