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Discussion Starter · #1 ·
98 v70 awd with 140k, new td04-19t turbo. Full ARD e85 tune at 18psi.

Most of the time it won't boost over 4psi, which I believe is what the wastegate is set to. But, every now and then it will, for no reason, allow full boost for a while and be alive and wonderful. 90% of the time is slowsville though.

You're going to say something about the TCV. Good idea. I just replaced it with the upgraded TCV and still just baseline boost with no change.
Another $80 down the drain. What am I missing? What else governs the boost?
And why don't we just use a secondary aftermarket boost controller and ditch the whole computer controlled boost thing on these anyway?
Thanks for any ideas.
 

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Is it a pierburg TCV? Or ARD/ipd MAC TCV. Check your TCV lines. We don't use boost controllers because that's not how the engine management system works. (Especially the 99+ ME7 cars where boost is load dependent not boost target dependent)
 

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Discussion Starter · #3 ·
It's the ard branded upgraded unit. I was hoping replacing the old stock unit would solve the issue. Nope.
The lines have already all been replaced, and I'm fairly certain they are correct. Is there a routing diagram somewhere so I can confirm?
Do I need to test wire voltage somehow?
But on my 98 you're saying I could just get a manual controller?
 

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Have you checked for vacuum leaks in the plumbing? I had an intake pipe leak that would seal its self some times and all of a sudden id get full boost.
 

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Well M4.4 is still load based power delivery, it just does it a different way than ME7. The tune sounds like the issue... Unless the CEL is flashing or something.
 

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Discussion Starter · #6 ·
Well M4.4 is still load based power delivery, it just does it a different way than ME7. The tune sounds like the issue... Unless the CEL is flashing or something.
It feels that way almost. Like there is some sort of safety setting that every now and then says, "ok, now we are safe to boost." No CEL. I'll double check with my scanner for pendings tonight.

All vacuum lines wre redone with silicone by the PO. Which somehow probably got screwed up. but everything looks solid to me.

I'm waiting for a call back from ARD tuning about it.
 

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The lines have already all been replaced, and I'm fairly certain they are correct. Is there a routing diagram somewhere so I can confirm?
It should be on the underside of you hood. Those lines are included on the sticker that shows all the vacuum tube routing.
 

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You know, i really don't know if that might be what you are having problems with but my wagon did the same thing and it turned out to be... Coolant temp sensor.
 

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Discussion Starter · #9 ·
i did a data logging video here https://youtu.be/2dZATIjodp4 you'll need to fullscreen to read gauges, and ff to 15 seconds
it keeps showing that the computer is reading like 40psi of boost, but my gauge only 5. I can certainly see that if it thinks it has 40psi it's not going to open the TCV.
What gets that measurement? I assume whatever sensor that is needs to be beaten and hung in effigy to warn the others not to misbehave.
 

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Discussion Starter · #10 ·
No luck or explanation as of yet.
For now, since they are cheap, I'm replacing the MAF, CTS, barometric sensor and throttle position sensor.
Not guessing this will fix anything, but $60 on eBay for the lot is worth a shot.
Any other ideas? ARD is out of ideas
 

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Discussion Starter · #11 ·
Also should note, I disconnected the waste gate arm and carefully drove. Unlimited boost early and consistent. So I don't think I have a leak anywhere.
 
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