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Old 05-01-2012, 10:16 PM   #1
Merko
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Default 95 WRX import - Full boost but no power?

Hi guys I'm stumped with a boost issue my car's experiencing. This seems to happen mostly in 3rd gear, and only about 50% of the time. The car will build full boost, but the car hesitates, has no power, and just seems to speed up as if all the boost was leaking somewhere. But this only happens like 50% of the time!! other times it boosts fine. 1st gear boosts perfectly, but I have noticed that 2nd seems to have a fair bit more lag than it did before - it'll get full boost (but no power), then give a big jolt of power at probably about 4,000rpm (the power used to build smoothly). Also the problem seems to be worse in cold weather (by Austalian standards lol. so like 10 degrees celsius).

Car is mostly stock, only things I've done is fix all boost leaks by replacing hoses and adding silicone turbo/IC piping, installed manual boost controller set to stock 11 psi boost, and blocked off the bypass valve a few weeks ago til I get a new one as the stock one had the piston stuck open. Also I can't remember if I reset the ECU after putting in the MBC 3 or so weeks ago, so I'll try that too.

There are definitely no more leaks (it wouldn't boost the other half of the time if there were) and the clutch is not slipping. I'm completely stumped :/ Could it be spark plugs/coil packs?

Also can't run error codes as check engine light doesn't work

Any help would be great!

Thanks
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Old 05-02-2012, 03:22 AM   #2
pmugabi
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My first check would be fuelling. Try replacing the fuel pump and also use a higher octane of fuel.

Spark plugs/coilpacks next. These cause a distinct misfiring feeling as opposed to the on/off power you are getting.

I used to get this when using the stock ECU map, after putting a more conservative map, this no longer happens. I concluded it was due to the car pulling timing due to knock.
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Old 05-02-2012, 08:24 AM   #3
Merko
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Fuel octane shouldn't be a problem. Already using the best pump fuel we have available here that other people have no trouble with (BP Ultimate - 98 octane).

If it was the fuel pump, wouldn't it have trouble at the higher rev boosting like with the 4,000rpm power jolt I described? Just seems to me that if it was the fuel pump my symptoms would be the opposite (ie. absolutely no power at high revs due to higher fuel demand)?

Think I'm going to try and fix my check engine light before I do anything else.
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Old 05-02-2012, 11:48 PM   #4
Merko
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Ok did ecu reset and now it's running perfectly again. This seems to happen every week or 2, then it'll have the boost issue again til I do the next reset...
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Old 05-03-2012, 04:40 AM   #5
pmugabi
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The ECU reset fixing the issue seems to point to the ECU pulling timing do to knock.
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Old 05-03-2012, 04:43 AM   #6
Merko
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Fixed my check engine light! Someone had removed it in the past, guessing to hide problems

Anyway, getting code 45: pressure sensor. Research tells me this is part of the boost control solenoid... but I'm running a manual boost controller with the stock solenoid plugged up. Though it still has the wires connected to it (disconnecting them results in the car not starting).

Any ideas how to solve this? Surely I don't need a new solenoid if it's bypassed with the MBC?
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Old 05-03-2012, 10:15 AM   #7
luka
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Quote:
Originally Posted by Merko View Post
Fixed my check engine light! Someone had removed it in the past, guessing to hide problems

Anyway, getting code 45: pressure sensor. Research tells me this is part of the boost control solenoid... but I'm running a manual boost controller with the stock solenoid plugged up. Though it still has the wires connected to it (disconnecting them results in the car not starting).

Any ideas how to solve this? Surely I don't need a new solenoid if it's bypassed with the MBC?
if you have an MBC you will always have Code 45 because if you boost above the stock boost pressure the ECU thinks the solenoid isn't working so it throws a code.
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Old 05-03-2012, 05:17 PM   #8
pmugabi
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Actually that's incorrect. Code 45 is usually only thrown if there is a short or open circuit to the MAP (pressure sensor). It is also thrown if the MAP sensor value does not change during a few minutes of driving. Reconnect it to the intake manifold and if it's not faulty, the code will go away.

Although it's strange that the engine won't start with the MAP sensor disconnected.
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Old 05-03-2012, 09:47 PM   #9
Merko
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Well I didn't just disconnect the sensor when I tried to start it. I removed the entire boost control solenoid so disconnected lots of wires. If I reconnect the BCS then the car just runs at 6psi boost coz it goes into safe mode. That's why I got the MBC. Think my only option is to clean the sensor and if that doesn't work, replace it. Unless there's a way I can bypass it...
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Old 05-04-2012, 01:50 AM   #10
pmugabi
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Have the MAP sensor connected and plumbed in but use the MBC to control boost. No CELs.
The boost control solenoid does not need any hoses connected to it, just leave it connected to the wiring loom.
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Old 05-04-2012, 05:30 AM   #11
Merko
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Yes it seems that was my mistake

Bought a replacement today off a crashed WRX at the wrecker for $25. But it turns out I swapped it for nothing as the reason there was a problem is that I'm a moron. When installing the MBC I blocked off every hose going to the boost control solenoid, including the one going to the pressure sensor. Hence no pressure getting to sensor hence error. Reconnected it and now no more error codes Unsure if it's running better now though, took it for a quick spin down some side streets and it might still be hesitating a bit, but maybe I'm imagining it, or maybe the ECU is still learning things after resetting it? Will see when I take it for a proper drive.
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