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The mkiv Supra Owners Club

stuttering/backfire when HOT and acc @ high revs


bodilx6

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6spd, TT, BPU.

 

When doing trackdays and everything is as hot as it gets, my engine lightly stutters and apparently spits a bit of fire when doing so.

I'm guessing this is a failed spark and there by unburnt gas in the exhaust.

 

Plugs are iridium and have MAYBE 20k on them, so no gappin'. I'm fairly sure (might be we just fixed them a bit) I got the plastic connectors on the coil packs replaced years back. Can they be causing issues again?

Please correct me, if replacing them isn't possible and I'm recalling a dream or something..

 

If I'm correct though, what would be my next thing to look at?

 

Also, if I inspect the coils, would I risk them crumbling, and then have a stuck car until I get parts?

 

(It's freaking hard to test after, as it ONLY see this on track - for now..)

 

Thanks

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With any problem like that its a process of elimination, start with the cheapest things 1st, although you can test spark strength by pulling each 1 and laying it on the top of the engine(runing) and connected.it'll be 1 of 3 things, plugs, connectors or coilpack.

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The plastic coil terminals shells only support, hold and lock the terminals themselves. Toyota do repair terminals with pre crimped terminals on short wires to replace the ones on your own loom, that may well be tired with poor tension. You hould change all twelves and the shells as well if they have gone brittle aging and break when you fiddle with them. Andy Blyth has put the part numbers in the technical resource section.

 

I would say at 20K miles the plugs are due a change. Maybe the coil packs are leaky, but do terminals and plugs first.

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Thanks Chris! (Yet again...)

 

This sounds right. It think actually it must be the terminals, I remember having been messed a bit with, point being them lasting a bit longer. We MIGHT have changed them and not just jerry-rigged them, but I don't remember as it was one of the first things I had done to the car 8-9 years back.

So, as I understand, I would get terminals with wires that I need to solder in?

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Thanks Chris! (Yet again...)

 

This sounds right. It think actually it must be the terminals, I remember having been messed a bit with, point being them lasting a bit longer. We MIGHT have changed them and not just jerry-rigged them, but I don't remember as it was one of the first things I had done to the car 8-9 years back.

So, as I understand, I would get terminals with wires that I need to solder in?

 

Raychem adhesive lined, heat shrinkable crimps in the red size are what you need.

 

http://www.ttiinc.com/object/fp_tyco_polycrimp

 

RS Components sell them, and many other electronic supply houses.

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