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Sharp cut/hesitation under load - 98 WRX import
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Old 14 Aug 2008, 11:18 AM   #1 (permalink)
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Unhappy Sharp cut/hesitation under load - 98 WRX import

Under heavy load/acceleration, my car has started bucking/cutting violently. It's feels similar to a hard cut rev limiter and enough to wake my other half up on a long journey.

I'd only had the the car 5 days when it first happened. And it 'seems' to have started since I accidentally put 95 RON unleaded in (purely out of habit). But it could well have been there before because I'd only driven it a couple of times. I've since stuck octance booster in to try to resolve it, but the problem keeps rearing up.

So, I'm guessing it's either fuel starvation or some kind of fuel cut?

It's fine pulling through 1st and 2nd but seems to happen in the higher gears. I'm not sure exactly when because I'm paranoid about doing long term damage. However, it definitely does it when accelerating from 80mph in 5th - unless I'm light on the pedal. Then it is more of a mild hesitation.

If you've made it this far... thank you. Now, please help because I'm getting a load of 'here we go comments from the missus...

p.s.
I've just bought a boost gauge to check for over-boosting (not fitted yet) and have an HKS FCD at the ready, waiting to be fitted...
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Old 16 Aug 2008, 10:56 AM   #2 (permalink)
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Re: Sharp cut/hesitation under load - 98 WRX import

you could try cleaning the boost solenoid on the drivers front strut turret. Its the one with either 2 or 3 hoses going to it and looks like a small cylinder.
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Old 17 Aug 2008, 03:32 PM   #3 (permalink)
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Re: Sharp cut/hesitation under load - 98 WRX import

Thanks. It's been driving me mad.

I've got a can of carb cleaner, so fingers crossed.
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Old 17 Aug 2008, 05:26 PM   #4 (permalink)
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Re: Sharp cut/hesitation under load - 98 WRX import

It sounds like fuel/boost cut, mine does the same as yours ie: usually in higher gears and when it does its usually over boosted slightly (1.2) ish.
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Old 17 Aug 2008, 08:21 PM   #5 (permalink)
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Smile Re: Sharp cut/hesitation under load - 98 WRX import

Problem sorted (thanks guys). Looks like I bought that Greddy Profec B boost controller for nothing...

Just in case anybody reading this post has the same overboosting/fuel cut problem, here's what I did (MY98 WRX).

Popped the two pipes off the bottom and side of the boost solenoid (attached to the driver's side suspension strut) and sprayed carb cleaner through the solenoid. Left it to stand for 5-10 mins, then connected the two green wires under the steering column to put the car into test mode. With the ignition on, this repeatedly activates the solenoid. While this was happening, I sprayed more carb cleaner in in short bursts. Just be careful with the paintwork, because the carb cleaner can get everywhere.

Then it's just a case of disconnecting the green wires and putting the pipes back on the solenoid.

Now it pulls all the way to the redline in all gears, without feeling like I'm hitting a wall repeatedly.

Properly boosting Scooby... Done.
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