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The mkiv Supra Owners Club

Weird missfire problem...Please help


garetheves

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Are you sure about the direction of the IAC's seal washer? The exploded view in mkiv.com shows (imo) the flat side towards the iac valve/stepper motor and the bevel towards the check valve.

 

Hmm good spot. That is the why i have put mine in. Really confused now. Might try it the other way round just to see if it makes a difference.

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its ambiguous isn't it. all i can say is that i too had it with the concave side on the valve side, and when i changed it my problems have been cured.

 

Rob

 

Which valve Rob, the 'check valve' (inside the inlet manifold) or the IAC valve (attached to the manifold)?

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Well the O2 sensor and Ignitor arrived this morning and still got the missfire. Tempted to swap the AIC back around and try it the other way with the new bits installed. Failing that im all out of ideas and will have to leave it to the garage on wednesday, just hope they can find it quickly so the labour charge doesnt creep up.

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Just had a good friend who is a mechanic round before it goes to the garage tomorrow. Bascially want to check everything we could before it goes in so that Labour costs will be to a minimum trying to diagnose. Did a compression test and all 9bar (thank god), tested all the sparks and No3 had a weak blue spark, regardless of which coil pack we used, changed the plug and had the same outcome. So its neither the plug or coil pack. Hes fairly confident this is what is causing the problem but couldnt narrow it down any further than that.

 

At least ive got something to tell the guys tomorrow and just very relieved that there's unlikely to be something major mechanically wrong.

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Gaz did you try a new igniter and also check the igniter connection and loom for any damage? maybe worth checking the emanage ignition harness wiring connections too.

 

Changed the ignitor for another second hand one (was working when came off car), made no difference. The connections to it looked ok but not tested them. Not got an emanage so no probs there :p

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Changed the ignitor for another second hand one (was working when came off car), made no difference. The connections to it looked ok but not tested them. Not got an emanage so no probs there :p

 

Sorry just noticed it was on the shopping list :D

 

Weak spark sounds suspiciously like a bad coil pack earth, but id look at all the following..

bad spark.jpg

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Sorry just noticed it was on the shopping list :D

 

Weak spark sounds suspiciously like a bad coil pack earth, but id look at all the following..

 

We did think whether it was an earthing issue but thought that if it was it would be more of a yellowish flame not a blue one. Could be wrong though. Youre gonna need to explain that diagram mate, im far from a tech head. :D

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