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High Idle and Hanging Revs
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Author:  colourclassic [ Mon Dec 28, 2015 8:27 pm ]
Post subject:  High Idle and Hanging Revs
New here, apologies if this has been answered before.

Just bought a '92 Vitara JLX with the injected 16v g16b. Car is manual and has ~240,000km

I threw in a new timing belt, tensioner and water pump yesterday and have been experiencing a high idle and some surging under acceleration. It ran perfectly before I touched it :P

One other thing is stupidly did, was spray carby cleaner into the throttle body and it's ports to remove some gunk. I let it sit there for a while before I started the car.

The car now idles at 1500rpm and takes a while to come down from a rev. It also feels like it surges lightly when accelerating.

Things I have done:
•Fully bled coolant
•Compression test showed ~180psi across all 4
•Checked cam timing was correct
•Valve lash adjusted to .006 across all 16
•Played with the air bypass screw on the top of the plenum.

One thing that I noticed, is that if I pull the plug out of the IAC valve, the engine will idle at ~600rpm and the revs will drop beautifully, which makes me think my carby cleaner damaged the solenoid.

Any other ideas on what went wrong?
Author:  Qthefun [ Mon Dec 28, 2015 8:58 pm ]
Post subject:  Re: High Idle and Hanging Revs
colourclassic wrote:
One other thing is stupidly did, was spray carby cleaner into the throttle body and it's ports to remove some gunk. I let it sit there for a while before I started the car.


My guess is this :(
Author:  alien [ Mon Dec 28, 2015 11:20 pm ]
Post subject:  Re: High Idle and Hanging Revs
I just had some high idle issues - take the plenum off the throttle body and i'll bet it's full of gunk. Clean that right out and you should be good.
Author:  Gwagensteve [ Tue Dec 29, 2015 8:25 am ]
Post subject:  Re: High Idle and Hanging Revs
Install a bleed on one of the the coolant hoses to the IAC valve on the throttle body. My guess is you have air in it. It's the highest point in the cooling system and will cause the symptoms you're describing.

Steve
Author:  colourclassic [ Tue Dec 29, 2015 11:00 am ]
Post subject:  Re: High Idle and Hanging Revs
Just installed a bleed and topped up the coolant - there was air but it hasn't fixed my problem.

In my first post i referred to the IAC as being problematic, I think I meant ISC - the one that maintains idle speed and is electronically controlled. As I said if i unplug it the idle drops and revs don't hang. Plug it back in and idle is up to 1,500 and revs are slow to go back down.
Author:  Gwagensteve [ Tue Dec 29, 2015 11:57 am ]
Post subject:  Re: High Idle and Hanging Revs
IAC is the same as ISC - "idle air control" is just the term for the bleed that is controlled by coolant temperature and bleeds air into the inlet past the throttle blade, increasing idle speed when the car is cold.

It's possible it's dirty and hanging open, but I speak from experience it can be very hard to clear all the air out of that area of the cooling system
Author:  colourclassic [ Tue Dec 29, 2015 12:34 pm ]
Post subject:  Re: High Idle and Hanging Revs
Hmmm, i'll try to bleed it again.

I've retraced my steps and made sure everything is in the same state it was before the problem arose. One thing I'm not sure of is that air bypass screw on the plenum. Any ideas of a ballpark setting, as I'm sure it's out of whack and I don't have a multimeter to set it.

I pulled the plugs and they are very chalky/lean. The surging under acceleration and slight popping from exhaust also suggests this.
Author:  Buckman [ Tue Dec 29, 2015 5:48 pm ]
Post subject:  Re: High Idle and Hanging Revs
Are you 100% sure the timing marks are lined up correctly
Author:  colourclassic [ Tue Dec 29, 2015 7:02 pm ]
Post subject:  Re: High Idle and Hanging Revs
Yep I rotated the engine twice after i set the tensioner and to ensure crank and cam were at #4 compression TDC.

Is it possible for the valve clearances to cause this? I'm sure I set each one to .006 but am willing to tear it apart again if theres a chance they might be the culprit.
Author:  Buckman [ Tue Dec 29, 2015 7:09 pm ]
Post subject:  Re: High Idle and Hanging Revs
I'll have a look on autopedia and see if it has a setting for that idle air screw. But I'm sure it will say something like adjust to 0.5% Co or something.
Author:  Buckman [ Tue Dec 29, 2015 7:23 pm ]
Post subject:  Re: High Idle and Hanging Revs
Valve clearance - .10 mm cold for in and ex
CO level at idle - .5%
CO2 at idle - 14.5 to 16%
Author:  SierraDan [ Thu Dec 31, 2015 6:44 am ]
Post subject:  Re: High Idle and Hanging Revs
Good chance its either blocked or full of air.
I pulled one of the hoses off and blew air into it after i ran a radiator flush through the system. It fixed the problem.
Author:  colourclassic [ Thu Dec 31, 2015 7:12 am ]
Post subject:  Re: High Idle and Hanging Revs
I installed a different IAC solenoid today with no luck. Also cleaned out the TB with compressed air.

As far as getting air out of the system, I put a funnel with a rubber sleeve into the radiator and fill it up, so the water is higher than the throttle body. Then run the car until thermostat opens.
I'm 99% sure I'm getting all air out of the system.

The car surges under acceleration and seems to have a slight popping or burbling out of the exhaust on decel. So stumped on this. I've double checked cam timing, there doesn't seem to be any air leaks. The only other thing that I touched was valve clearances (~0.15mm on EX and IN) but I don't see how they could cause this.
Author:  colourclassic [ Tue Jan 05, 2016 3:52 pm ]
Post subject:  Re: High Idle and Hanging Revs
Took the car to the local Suzuki place to have it checked.

Turns out TPS is dead/dying, causing most of the issues. Also o2 sensor on its way out and EGR valve blocked.

Funnily enough all of which have nothing to do with my timing belt change, so luckily I had that right. :)

Thanks for all replies.
Author:  christover1 [ Mon Feb 01, 2016 11:15 am ]
Post subject:  Re: High Idle and Hanging Revs
Sometimes disconnectin g battery, so ecu can reset to factory is helpful, after a problem has been fixed
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