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1.8t boost issue please help

698 Views 6 Replies 4 Participants Last post by  gtimitch
Hi all, I've got a 1.8t agu. And it's started with a boost issue, it's very intermittent. Basically when your come on boost it boost as it should for a split second, then holds back until about 4-5k revs then it boosts as it should. I've changed the n75 and plugs with no change. Am I right in assuming it could be the dv or the n249?
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Possibly the d.v, just fitted a forge updated spring and serviced the d.v on mine as it was going on and off boost, suspected the spring was weak.
Could be that or the wastegate actuator spring could be worn so its basically peeing the boost away.

Mine suffers a bit like this as its high miles.

Also check for boost leaks, perished rubber hoses etc.

If its otherwise running fine with no missfires then you can rule out the ignition amp/maf.
Yeh it runs mint it's just on boost it's intermittent I'm having a full diagnostics done tomorrow where he plugs it in and sees what it's doing whilst driving and have a full check on the pipes. Debating weather to keep it. It's been a mint car.
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If its the wastegate actuator diagnostics won't show too much, apart from N75 requested boost against map sensor (does the agu run a map sensor actually?)
No MAP or N249 on an AGU.

At 130k miles on mine with 6yrs of stage 2, doubt it's the actuator.

What DV do you have?


I presume you have changed all the small VAC/boost lines for silicone? Do this first if you haven't, don't waste money on other stuff.
The dv is just the standard one, ive just tried my mates forge 007p on it and it didn't make no difference, I've not changed any of the pipes it's a totally standard car but I've checked and there not perished, I've had the diagnostics on it, it brought up a maf sensor issue but that's cause I unplugged it, and it was still on the system, cleared the fault and it didnt come back. Totally scratching my head with this one.
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