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The mkiv Supra Owners Club

Another Boost problem.


s3upra

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Could really do with some help from the tech bods out there.

Heres the story so far-

J spec tt,auto 1994, always felt a little slow so fitted a boost gauge plumbed in as per http://www.mkivsupra.co.uk/ to confirm any boost worries-

first turbo boosts to 0.5/0.6bar,then at around 4000revs boost drops to 0.2/0.3 bar and stays like that till the next gear change(then same happens).

Checked hoses,all fine,checked iacv vsv and theres no resistance(open circuit)-brilliant i thought problem solved.

Switch to TTC so i can bypass said vsv(temporary measure only)

Now boost starts at about 3000revs and by 4000 im getting 0.4 bar steady to the redline.

This sounds like T2 not working-any ideas.

I have checked the following-

The Bov is working(blow test)

 

The wastegate actuator is working.

 

The iacv actuator is working (in TTC)

 

 

The pressure tank is holding pressure fine infact after a run the EGCV remains open,then if i remove the pressure hose to it-it closes fine,then opens as expected at 4k ish.

I assume this isnt normal-ie i thought EGCV should be closed at low revs?

Any help gratefuly recieved!

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are you decatted? If not, take the first cat out, turn it upside down and tap it. If lots of black ceramic bits fall out, cry/swear/shout/scream. Seriously, it's probably the quickest and easiest way to tell if no. 2 has popped.

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Just a thought, but it might be worth checking the actuator arm is actually still attached - it's just a little C-lip holding it in place. You'll need to take the top pipework and the heatshield off though.

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by wired open,do you mean physically(tied with wire?),not sure this will help as part of my problem seems to be that it IS open(even at idle).However will give it a try.

Thanks.

Any other ideas,before i start trying to accept the worst.

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So the IACV and EGCV are holding open in TTC and still no joy. Just to confirm the EGCV is working, did the exhaust get louder with it open?

If not then maybe somethings not quite right with the EGCV.

All I can think off mate apart from the nasty option.

 

Cheers

 

Mike

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As Bob said mate, I'd just get that CAT off first instead of fiddling around with other bits and at least confirm/reject your big worry about Number 2 going down the pan - as hurtful as that may be. :(

 

You never know what else you'll find too!

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  • 1 month later...

Well i couldnt get first cat off,so decided to re-check everything every actuator and vsv-even held the wastegate closed with a large spring!No difference at all.

 

Finally sorted this-if anyone is remotely interested!

Took car to Mark at Phoenix (top bloke-cant recommend his work highly enough).

Even he thought the problem was a bit bizarre,after trying a few things, he ended up removing turbos(there were no ceramic bits in 1st cat).

Turbo 2 looked fine,but the exhaust exit side of it was clean-looks like it hasnt been doing anything for years-possibly ever.

Mark swapped them for a good(i hope!) set of used ones and told me the car was fixed.

After 1 hour stuck in crawling traffic on m25/m3 in the peeing rain,finally the sun comes out and a few dry lines start to appear.Put my foot down and OMG,realise i have been driving a low compression n/a for 3 years.

The difference is astounding:d

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