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Another One Of Those Missfire/hesitation Threads

Slattery Gts-t

By Slattery Gts-t,
in Engines & Forced Induction

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Slattery Gts-t Contributor

Slattery Gts-t

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I recently brought an R33 GTSt series 2, on the way home i noticed from 3500 under boost it just doesnt pull very hard. I changed the plugs to PFR5G's gapped to .7 and just replaced the splitfire coils with yellow jackets but didnt help so i assume my splitfires are ok.

The car runs good for about 5 mins then starts playing up like this sometimes when it hits 5000 revs it misses and backfires, If i stop the car turn it off restart it and take off its fine for a few mins then plays up again

As far as i know the car has a high flowed turbo thats all i know about that, 3 inch exhaust and dump pipe running factory boost. Im not sure where to go from here its getting to be a pain! maybe AFM ? i dont think its Rich & Retard as it does it at only a few psi

Oh and i have searched and read numerous theads on this forum i dont mean to offend anyone by posting another thread on this topic but i dont think i have read one where restarting the car temporarily fixes the issue

Borci88 Veteran

Borci88

Posted
Posted

Sorry I can't help you with this but all I can say is I have the same problem. With my problem it pushes you back in the seat around 2.5k and then from 3k - 5k or so it becomes a lot of noise and not much go and after that it starts to pull a lot harder. Is that like yours? I've just put in new plugs and Yellow Jacket coilpacks and it's still doing it. I think you and I might have a Vac/Boost leak somewhere..

Slattery Gts-t Contributor

Slattery Gts-t

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Thats pretty much exactly what its doing!

Just read the fault codes and its coming back with code 21 = Ignition signal, Ill reset the ecu by disconecting the battery and see how i go

Slattery Gts-t Contributor

Slattery Gts-t

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Problems back!

Disconnecting the battery fixed it for a day then it started playing up again, since then i have replaced the AFM with a brand new one but the problem is still there and still intermittent like before, iv got no idea where to go from here

zebra Grand Master

zebra

Posted
Posted

highflow turbo + standard ECU = asking for trouble of the kind exactly like you are describing.

standard boost or not the turbo is flowing more air than the ECU can handle so its chucking a hissy fit

Slattery Gts-t Contributor

Slattery Gts-t

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I cant seem to lower the boost, it boosts to 0.5 Bar then after 4500 revs the boost starts building with revs until redline and then its boosting 0.8 - 0.9 Bar.

I have a vacuum line running straight to the wastegate bypassing the boost control solenoid. Does the boost rise because the wastegate cant flow more exhaust gas due to it now being highflowed ?

GTScotT Grand Master

GTScotT

Posted
Posted

Having given the fault code for ignition signal surely you would want to test the CAS?

I too am having this problem as is another member and i am certain its a damaged CAS.

I'll give mine a go soon and report back, not sure how early ill be doing this but sometime next week is on the cards.

Slattery Gts-t Contributor

Slattery Gts-t

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Definatly rich and retard, I did some data logging and when the AFM voltage reaches 4.4 or so the timing pulls right back to 0 Deg BTDC and injector duty shoots up

Any ideas on how i can stop the boost creeping from .5 bar to .8-9 at redline ?

Rolls Grand Master

Rolls

Posted
Posted

Any ideas on how i can stop the boost creeping from .5 bar to .8-9 at redline ?

Run the standard wastegate spring, it sounds like you have an rb20 item in there if its running 14psi. That or there is a leak in your wastegate vacuum hoses

Sparky206 Enthusiast

Sparky206

Posted
Posted

I cant seem to lower the boost, it boosts to 0.5 Bar then after 4500 revs the boost starts building with revs until redline and then its boosting 0.8 - 0.9 Bar.

I have a vacuum line running straight to the wastegate bypassing the boost control solenoid. Does the boost rise because the wastegate cant flow more exhaust gas due to it now being highflowed ?

Its a vicious cycle, the car hits rich and retard, dumps in a whole lot more fuel, which in turn helps spool the turbo even more. I spent nearly 2 years trying to figure out what was happening and why i couldnt get my boost to stabilise. I only ever found one solution that allowed me to keep the boost stable, and that was putting a 2.5" restriction plate at the end of the exhaust. No idea why it worked, but with that in i could set the boost to whatever i wanted and it would hold it to redline, take it out and it would do what you described, just keep building boost to redline. In the end i just got a tune to 14psi and let it do what it wants, its seriously the least painful option, trying to run anything over stock boost with the standard ecu and tune is just a massive headache with rb25s, you need to either pick standard or pick your mods then get a tune, there isnt really an inbetween that wont cause issues

Rolls Grand Master

Rolls

Posted
Posted

Its a vicious cycle, the car hits rich and retard, dumps in a whole lot more fuel, which in turn helps spool the turbo even more. I spent nearly 2 years trying to figure out what was happening and why i couldnt get my boost to stabilise. I only ever found one solution that allowed me to keep the boost stable, and that was putting a 2.5" restriction plate at the end of the exhaust. No idea why it worked, but with that in i could set the boost to whatever i wanted and it would hold it to redline, take it out and it would do what you described, just keep building boost to redline. In the end i just got a tune to 14psi and let it do what it wants, its seriously the least painful option, trying to run anything over stock boost with the standard ecu and tune is just a massive headache with rb25s, you need to either pick standard or pick your mods then get a tune, there isnt really an inbetween that wont cause issues

wut

2.5" plate after the end of the turbo? that is the most retarded idea I have ever heard, why didn't you just get it tuned properly from the get go?

Sparky206 Enthusiast

Sparky206

Posted
Posted (edited)

it was at the end of the exhaust, a few people mentioned it as a common problem with supra's , and a few had had success with it here. It was by no means a solution, but i was trying to figure out what the issue was before i went and got a tune

Edited by Sparky206
Rolls Grand Master

Rolls

Posted
Posted

Well i just had a look at my ecu and it has one of those gold mines stickers on it

That is your problem right there, go get a stock ecu. Those mines ECUs are rubbish, make it run way too much timing, way too rich and just suck ass.

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