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Boost intermitent,


Joel93
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Hi iv realised that after driving my impreza for 30 mins or so after a few hard accelerations the boost drops from 14psi to around 7psi. From what I've read this is limp mode but there is no CEL on, car has a cat back exhaust a panel filter and remap. Pulls really nice until boost drops off, after turning car on and off for 5 mins bost I'd back up to normal? Any ideas? Thanks 

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do you have an aftermarket boost controller fitted to vehicle if so my be worth dropping the max boost down a tad i had the same issue when it hit peak boost it shuts fuel off for a second and then runs normal.

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It's a 2004 wrx and I only had the car on the road a week, map was carried out about 8 years ago, there must be somthing bost related tripping it into low boost setting because its only happening after a few hard accelerations 

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Yes ,Lower octane fuel can cause it to lean off under boost,  which in turn might cause limp mode .

Have you got any proof it's been mapped ? 

As 14 psi (just under 1 bar) is a low boost target for a mapped car ,admittedly that could just be a inaccurate boost gauge .Most mapped cars will have the boost target upped to 1.2 to 1.5 bar pending on mods and engine condition .

If you dont have proof of a remap standard  boost target would be between 0.6 bar and 0.8 bar , you'd have to Google your model and year specific oe boost target. 

So if you're hitting 0.9 bar on a standard map boost target ,it could well be overboosting and that might cause it to go into limp mode .

Although you haven't got a cel light , I'd suggest to get the codes read while it's in possible limp mode . As it might log a minor fault on the ECU but not show a cel, due to it resetting when you restart the car .

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No it just has a td04, drove 180 miles  today and still boosting fine, parked car up and when to the beach.

Next drive I put my food down 1st gear boosting nice, 2nd gear boost to 14-15 psi, 3rd gear boost to 15psi then dropped back down to 7psi it then stayed like this until I turn the car off and back on. It seams to droop off as I hit 5000rpm ish. Is this over boost? After trialing out it can pull boost all day in 1st and 2nd but a hard pull in 3rd upsets it. 

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