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The mkiv Supra Owners Club

Very strange holding back/misfire


chrisavila100

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Ok a few days ago my strange misfire returned:(

The problem: when on 1/2 to 3/4 (more noticeable) and full throttle i get a misfire/holding back when going from turbo1/2!

 

It boosts up fine on the first turbo then as the 2nd turbo kicks in it hold's back/misfires (not car shaking, more like a very strong head wind with a sort of farting coming from the exahust) then once the 2nd turbo is on full boost all is fine again!

 

If i floor it at say 2500rpm there is only a slight holding back when no2 comes on line, its much more apparent when on 1/2 to 3/4 throttle! and only happens when no2 starts to kick in! once kicked in its fine to the red line!

Although the car does feel a bit less responsive during "normal driving" there is no miss/holding back during driving the car normally!

 

Ok now the strange bit: if i reset the ecu the problem goes away:search: then after a few days it comes back again!

 

When i reset the ecu the car feels great,pulls really hard no miss at all! and does so for a few days(any where from 80/250 miles then the problem comes back:(this problem first happened about a year ago lasted for about 3 weeks! and then had been fine until last week!

 

(New toyota plugs fitted at the last service 5k ago)

 

I have searched most of the misfire threads and i guess it could be the coilpacks? But why would reseting the ecu fix the prob for a while??

And seems strange the car has run fine since it last happened a year ago?

 

Im really confused about this problem, ive checked for error codes but nothing is shown!

 

Hope someone can help:)

thanks chris...

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Cheers for the help so far guys!!

 

I did manage to read some of the replies to this thread before the rest got wiped!

 

I went over to see damianC last week to check a few bits, we checked the coil pack connectors and they look in A1 condition not brittle at all! they came on and off with ease!!

 

We then took the car for a test run, the miss did not seem as bad as normal but was still there! he did notice that the miss was at 0.6bar when the 2nd turbo was coming online!

We also noticed that the cars boosting to, 1st tub 0.75 holding@ 0.65, 2nd tub 0.95 holding@ 0.8!

Now the only mods are 2nd decat,nurspec r, and blitz sus induction!

Damian was surprised it was boosting so high on a stock uk spec? is this normal with the mods ive done?

 

This has made us think maybe the stock toyota plugs(fitted 8k ago) might not be up to the job? what do you think??

 

Im going to buy some ngk bcpr7es plugs and try these out! in the faq section it states these are for cars up to 1bar ie next step up from stock!

Do you think the stock plugs would have probs running the boost levels ive stated?

Thanks again guys, will let you know what happens once we change the plugs! and if no change then its looking more like a faulty coilpack or 2?

cheers chris...

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Cheers mate i really hope so!

 

The only thing i find very strange is when it first happened about a year ogo i was running stock toyota plugs with 55k on them! the prob cured itself after about 4 ecu resets then was fine for a year until now!

 

The plugs were replaced at the last major service as they had now done 65k from new!!

Ive now done 6k on the new plugs (stock toyota ones) and if i reset the ecu the prob goes away for a few days!!

 

Seems very odd to me!

 

But will try the colder plugs and see how things are!

 

P.s do my boost levels seem high for a stock car? in the winter it was peaking at 1bar!! and this is with an old stock smic, which when damian looked at it said " thats fuc#ed!!

 

cheers chris...

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had the same thing mate, boost stutter.

 

it would start boosting felt like it completly stopped and then come on again all the way up the revs.

 

i firstly replaced my spark plugs, which did most of the trick.

 

but then replaced the 02 sensor and job done

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Cheers mate!

Should be getting some before i go to work today, but on lates till sunday!

Will finish around 5.30 sunday so if your not busy we could change them then..(lets hope its a dry day)

 

 

"lockys96"

but then replaced the 02 sensor and job done

 

Might have to try the old lemon trick;)

 

Cheers guys..

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