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The mkiv Supra Owners Club

Spluttering on WOT??


raddys
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Hi guys

So I noticed the other day that when I hit full boost the car splutters like it has a misfire, it's fine under 4k but anything over 4.5/5k when I'm on WOT it splutters, originally I thought it may be boost pipes but I'm not sure.

 

Bit of info on the car: 93 TT auto, 46k and bpu (bpu was done about 5k ago) serviced 5k ago and 1k ago

 

Just wondering if anyone's had the same experience or knows what it may be before I start pulling stuff apart?

 

Many thanks, Grant 😊

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I'd start off with checking the resistance on the 6 coil packs, think it should be 4-6k ohms but thats from memory which fades as I get older. Next would be the fuel pump pressure if you have a means to do that to confirm there is enough fuel reaching the rail.

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Have you pulled the plugs for a look, could be mixture is too rich or weak, what grade are you using? presumably, this has only just started happening? Has anything been done recently?

 

No but that's next on my list, I can't remember what plugs went in but they were the ones recommended for bpu on the forum, yes only recently and no nothing has changed on the car, il try the plugs and coilpacks 1st il be back if that doesnt solve it lol

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Mine also suffers with this, although I'm big single.

 

I've tried:

 

New spark plugs

New coil packs (oem)

2nd hand ignitor

Coil pack plugs

 

But it's still there. Yours and mine might be unrelated reasons, but I'd be interested to know if you solve it, as it might give me another avenue to try

 

 

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Mine also suffers with this, although I'm big single.

 

I've tried:

 

New spark plugs

New coil packs (oem)

2nd hand ignitor

Coil pack plugs

 

But it's still there. Yours and mine might be unrelated reasons, but I'd be interested to know if you solve it, as it might give me another avenue to try

 

/QUOTE]

 

I had a throttle body sensor fail and it was miss firing like crazy under load once upon a time, tried everything like you. SRD guys spotted it coming on and off in the logs, longshot but might be the cause.

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Had a supra with similar symptoms turns out the fuel pump was on the way out.

 

Might be worth getting a fuel pressure tester on there if you get no luck with ignition side of things.

 

Does the problem still occur when you are running factory boost level, or only at BPU boost?

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I had a throttle body sensor fail and it was miss firing like crazy under load once upon a time, tried everything like you. SRD guys spotted it coming on and off in the logs, longshot but might be the cause.

Thanks buddy, at least that gives me another avenue to check 👍🏻

 

 

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this happed on mine, I had it rolling roaded and after bpu it did 234bhp, misfiring at the top like crazy, he changed the 02 sensor and fuel filter plus cleaned out the chambers where plugs and coils sit as he said the spark could ark in there or something and re rolling roaded it at over 400bhp.

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The curse of the splutter! I had this for months and literally went through the entire car to try and eliminate everything. It turned out I had a variety of things to sort on my single, but the ones I would pay closest attention to (radys and mk4gaz although I know you've done some of these) are coilpack wiring, ignitor, coilpacks (new oem replacements or a conversion and remove ignitor). I redid a large part of the ignition wiring just in case, did a coilpack conversion to better coils and removed the stock ignitor too.

 

Also the ebay coilpack connectors are shite and my original set, one of the locking tabs unlocked so I wasn't making a good contact on one pin which never helps. I then sourced some better ones.

 

Check for overboost/boost cut protection on standalone

 

Fuelling, as mentioned, check this.

 

a worthwhile thing to do is get the car to a reputable dyno tuner where they can give it a proper once over and do some testing. Could save many hours of fault finding when they may find it quickly....

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