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General => The garage => Topic started by: sKrEwBaLL on 06 January 2004, 22:10
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My 8v digi started to misfire BADLY tonight, just started all of a sudden, causing quite violent juddering and the rev counter was going mental. Shat myself and pulled over and the car was still misfiring and the rev counter was still jumping around all over the place. I could smell petrol so I left it for a bit and then started it up and it was doing the same thing. I have always had a feeling my ISV is a bit dodgy so I disconnected it and the misfiring stopped!??? ??? I left it disconnected and managed to drive home fine albeit with an idle speed of 500rpm.
How could the ISV cause misfiring, because I thought it only came into action at idle? Also, will it make any difference if I just leave it disconnected for now?
Cheers
Neil
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Sounds like you got an air leak somewhere.
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OK I was not imagining things last night. This morning was exactly the same, the car was misfring badly with the ISV connected, and OK with it disconnected, although it wont idle until the car has warmed up. Could this be a faulty ISV?
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sounds like a dodgy ISV if it idles fine without it, take it out and clean it out with petrol then spray a bit of WD40 in it
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sounds like a dodgy ISV if it idles fine without it, take it out and clean it out with petrol then spray a bit of WD40 in it
The weird thing is, its not the idle... it actually misfires and the rev counter jumps about all over the place when you are revving it. I dont understand how the ISV can make it do this ???
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well i had this with mine, even with the ISV disconnected, turned out to be the hall sender in the dizzy.
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Expensive to fix..?
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i ended up gettin a new dizzy as i couldnt get the pin out of the rear of my existing dizzy
?80 for a new bosch dizzy, now it runs sweet as a nut (with the ISV still disconnected!!)
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Did you have to adjust your idle to get the car to idle properly with the ISV disconnected..?
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Did your rev counter go mad when the ignition was on?
Like it flicked up really high?
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Yes, the rev counter was jerking about all over the place and the car was undriveable
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this is exactly the same as what happened to mine, farted banged misfired big puffs of smoke out the back, rev counter bouncing all over the place
replaced dizzy, hasn't done it since, also check all electrical connections for damp, green mould etc
with the ISV disconnected i just idle of the idle screw which is perfectly fine
ISV only compensates the idle when under load from the likes of rear window lights and fan all being on
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Mine was bouncing all over the place. Got my coil changed and it went away
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I think I'll get my idle sorted using the screw and just leave the ISV disconnected. Its more hassle than its worth I reckon ::)
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If you are running the car with the idle valve disconnected then you probably have an air leak somewhere.
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I think you may be right, but I'm not sure where the leak is
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If the rev counter is going all over the place that would tend to indicate an ignition problem. Could be that disconnecting the ISV is disguising the real problem.
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Don't get me wrong as it could still be a vaccuum leak but I think I would try what Gambit has suggested and check the ignition side of things first.
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Yep i'd go along with that, the hall sender seems to be always worth a look.
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It shouldn't hurt leaving the ISV disconnected, assuming the engine's idling ok. the ISV only saves the car from stalling, if the engine hunts, you'll hear it clicking. If it wasn't clicking before, then it probably isn't doing much, mine works fine without. With vacuum leaks though, you really have to check nearly all the hoses except cooling ones. Takes a long time, and is a real pain in the arse, try the simple things first!
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The car is running perfectly now with the ISV disconnected. I had to adjust the idle, and it cuts out for the first minute or so when starting from cold, but I can live with that. :)