Curing the Idle Air Control Valve "Death Rattle"

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Curing the Idle Air Control Valve "Death Rattle"

Postby Ian Linden » Sat Sep 20, 2003 08:44

If you can hear a ticking under the bonnet when the engine is idling, it is probably the IAC Valve, but you don't have to tolerate it - in fact, you definitely should not - the noise you hear is it gradually self destructing, and they are very pricey.

They seem to get gunged up, and the usual symptom is a loud "rattle"; I surmise this is the valve sticking until the solenoid force overcomes the stiction, then it frees and whacks across to the other end of its travel, giving itself a right hammering in the process.

Get an aerosol can of Wynn's Fuel Injection Intake and Carburettor Cleaner. With the engine running, remove the inlet hose to the valve (refer to pages 6E-8 and 6E-9 in the Electronic Fuel Injection Section), and spray about 40 one-second bursts into the inlet of the valve. If the engine appears to be about to stall, wait till it recovers, and continue spraying.

A photo "Where to Spray" is at http://www.suzuki-cappuccino.com/albums/454.jpg

This has cured the problem on several Cappos.
Last edited by Ian Linden on Thu Dec 04, 2003 17:38, edited 2 times in total.
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Postby Murray Betts » Sat Sep 20, 2003 13:55

In addition to Ian's tip, if your IAC valve is ticking loudly, check the duty cycle as described in the workshop manual (available to view on-line on this site to members).

It's a very straightforward check (just follow the instructions), and a single screw to turn in order to adjust it.

You need either a digital multimeter reading duty cycle, or an analogue multimeter will work reading DC volts (both readings are given in the manual; duty cycle is preferable, but analogue volts will be near enough; it's not absolutely critical in practice).
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Postby Al Muncey » Fri Jul 23, 2004 08:48

How loud does this tick have to be before it's an issue? With the bonnet up and the engine idling, our IAC valve is doing it's ticking thing. However with the bonnet shut, sitting in the drivers seat with the roof on and windows up it's practically inaudable. Should I worry?

If it is a solenoid hammering back and forth as you describe, surely some noise is inevitable.
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Postby Ian Linden » Fri Jul 23, 2004 12:03

I think that in "normal" operation, the solenoid is inaudible. If you can hear it with the bonnet shut, it's the "bad" ticking.

I prescribe a can of Wynn's for your Cappo, and a can of something nicer for you, when you have used the former :D
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Postby Gemma Viles » Wed Apr 05, 2006 10:40

just an update on the 'death rattle' !

my cap was suffering from this and it was slowly getting worse....I used Wynns and it did go away but came back again after a while.

Have tried some fuel additives and again it went and came back.

Next on my list was Shell Optimax every time I filled up and this seems to have done the trick. Took about 4 tanks took sort it, but the cleaning additives in Optimax seem to do the trick.........plus I'm sure it goes faster now too :lol:
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Postby Lisa Balsom » Wed Apr 05, 2006 11:38

When we got our car it had "The IAC Rattle". We tried the injector cleaner and the noise went away for a short while and then returned. It became so irritating that we decided to strip the IAC valve and investigate.

Once stripped (great care required) we found that deep in it's bowels, there is a small piston and spring. On the end of the piston there is an O ring, whose purpose is presumably as a damper and for noise suppression, with about 1/3 of the O ring worn away. The worn area had allowed metal to metal contact and left a witness mark on the back of diaphragm's steel centre which it impacts upon.
We removed the piston and replaced the O ring with a manufactured replacement, rebuilt and refitted the valve and viola! the IAC noise had gone. :D

How long this repair will last is hard to say, but we only used it as an experiment to prove a theory, and upto now it has worked.

Whether I would reccomend this avenue, I don't know as it isn't hard just damned fiddly! :banghead:

Your noise may not necessarily be this but if it is, this may be the fix, or a new valve of course. :)
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Postby Ian Linden » Mon Jun 18, 2007 10:48

Gemma Viles wrote:just an update on the 'death rattle' !

my cap was suffering from this and it was slowly getting worse....I used Wynns and it did go away but came back again after a while.

Have tried some fuel additives and again it went and came back.

Next on my list was Shell Optimax every time I filled up and this seems to have done the trick. Took about 4 tanks took sort it, but the cleaning additives in Optimax seem to do the trick.........plus I'm sure it goes faster now too :lol:


Delighted that the problem had been overcome, but I take leave to doubt that the fuel could do that, because only fresh air passes through the IAC Valve - the cleaning additives do not appear to have a path to reach it.
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