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Post by carl4x4 on Mar 16, 2019 10:42:05 GMT
Hi, I'm trying to diagnose whether my idle air control valve is working on my '99 engine. This video shows how far the bellows move (only about 1/2mm) I have tried cleaning with throttle body cleaner but there doesn't seem to be much gunk in there and it still only moves a fraction. Is this small amount of movement normal or does it need fixing / new one ?
The video shows me connecting the terminal on/off when ignition is on.
thanks
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Post by dadbif on Mar 16, 2019 17:11:24 GMT
I would expect to see a lot more movement than that, have you tried stripping it down any further?
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Post by dadbif on Mar 16, 2019 17:19:52 GMT
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Post by carl4x4 on Mar 16, 2019 19:21:48 GMT
I saw that thanks, it's the mk1 version which is different
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Post by Zed. on Mar 16, 2019 20:36:49 GMT
if the isv is innoperative, is it electrical or mecanical (gummed up)? if electrical have you tested it for continuity / resistance? if mecanical try soaking it in solvent like petrol / thinners / meths / brake&clutch cleaner / semtex / vinegar / white-spirit as this can disolve the gack thats blocking the movement Rich.
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Post by carl4x4 on Mar 16, 2019 21:26:37 GMT
if the isv is innoperative, is it electrical or mecanical (gummed up)? if electrical have you tested it for continuity / resistance? if mecanical try soaking it in solvent like petrol / thinners / meths / brake&clutch cleaner / semtex / vinegar / white-spirit as this can disolve the gack thats blocking the movement Rich. The electrics work, I just have no idea how much the thing is supposed to move, at the moment it's about 1/4mm which can't surely be right...?
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Post by Zed. on Mar 16, 2019 21:43:57 GMT
usually (on similar systems like Bosch on Vauxhall / Volvo & Ford) the plunger moves sufficient to block & allow air to pass between both ports - to test its handy to 'blow' in one port & see if it modulates / allows flow when energised electrically (or not?) sorta Rich.
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Post by carl4x4 on Mar 18, 2019 17:33:43 GMT
Hmm, looks like I might have the frequency set up wrong on the ECU, so the duty cycle could be opening only a small amount on purpose. The mk1 1.6 was set to 160hz and the mk2 uses 500hz, time to check when I get home!
edit: nope, base frequency was set to 488hz which is good, but ECU currently in Manual duty with idle PWM duty set at 30%. That might be why the valve is only opening a fraction and keeping warm idle up at the target RPM of 1200+
I tested the valve again this time to ground and it opened a good few mm so I'm happy the cleaning seems to have got it to work again for now (I've ordered a used spare in case it goes wrong again)
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Post by martiny on Mar 19, 2019 15:57:29 GMT
30% duty cycle would only just begin to open my (Mk.1 1.8) IAC valve. They vary a bit but having tried a couple I think starting to open at around high-20s percent and fully open by mid-60s percent duty was probably typical.
Mk.2 version has higher flow as it does the jobs of both the IAC and the thermal valves on the Mk.1, so it might behave a bit differently but probably not a dramatic difference.
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