Boost Spiking / Lumpy Throttle Response - Subaru WRX Forum
 
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post #1 of 6 Old 12-03-2010, 02:19 PM Thread Starter
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Boost Spiking / Lumpy Throttle Response

Hi,

first off - i`m from germany, so apologies for my not so perfect english

Right, got myself a 01`WRX Bugeye, here`s the mod list:

- 3" turbo back
- open air intake
- stock turbo (not sure what turbo came in this year ?) with a remap from racedynamix (from the UK)

Car drove absolutely fine, but during the last weeks i could feel that there was some issue with the boost goin on.

Up to 3500-4000 rpm everything was alright (felt like boost was rising up too fast though), then suddenly boost drops dramatically, builds up again, drops again, builds up etc.

Had no CEL light so far but i was checking for vacuume leaks and so on, couldnt find any.

The car was pretty much faster on half throttle than on full throttle.

Made another test drive, tried to see what happens in higher gears (the higher the gear - the worse it was) and boom - flatout in 4th or 5th i got a CEL.

The car was accelerating kinda smoothly without any bogging or hesitation, so its not a misfiring issue, at least i highly think so, had one before on an older Impreza and it drove me nuts.

Went to subaru to read out the error code, unluckily it didnt save any (despite the CEL was still on of course), told him to reset the ECU and delete the code, done - no more CEL light on.

That was pretty much 2 weeks ago, in the meantime the car stood for a while, and thanks to the lovely temperatures right now i didnt feel like working on it.

Started it this morning, immediately got a CEL light again (?), so i tried to resolve the boost issue.

I ran a straight line from Turbo housing to actuator (bypassing the boost control solenoid thingy), had a little run around the block, everything seemed fine, the car hit like 7-8 psi (which i think is stock actuator pressure) and reved up smoothly without any drops in boost.

On the way back though it started, idle went up to 1500 rpm (on a way to a redlight idle goes up and down and up and down) and the throttle response was very lumpy, especially on part throttle, WOT is just fine.

Unhooked the battery for 30 mins and put the lines back to the stock BCS, still CEL light, of course still the overboost issue (so i HIGHLY think the BCS is bad (?)), and now i got the lumpy throttle as an extra for free, so instead of fixing it i made it worse

Will take an extensive look on the vacuume lines tomorrow, i also noticed that the ground wire is not the tightest on the battery, cant tighten it more though or ill snap it, will put on a new pole tomorrow.

When i unhooked the lines from the BCS, i should have plugged em with something, he ?

Anyhow, any small advice would be nice, lets see what Subaru says tomorrow, maybe it saved an error code this time ...
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post #2 of 6 Old 12-03-2010, 03:20 PM
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No CEL... very weird as it should hold/store the code.

My guess is the solenoid as well. Do you have access to a 3port BCS there and another tune ?

Paul
2002 WRX Sold
2007 WRX Sold
2007 STi totaled
2007 Foz XT sold
2007 MS3
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post #3 of 6 Old 12-03-2010, 05:13 PM
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Yeah I'd say either the solenoid... The gate/actuator is still good if you hooked boost direct to it and topped out at 7-8 psi.

A bad ground could cause issues like this as well though.

-Chris
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post #4 of 6 Old 12-04-2010, 05:34 AM Thread Starter
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Went to Subaru, they were too busy this morning, made an appointment for monday to get it read out.

Fixed the battery pole, its on there fine now, but i still got the lumpy idle and throttle response, mainly in first gear though, from the outside it looks like i cant drive pretty much.

I noticed that when turning the ignition/engine off, it takes a sec longer now until it really shuts off, it also sounds like the engine is not running constantly on 4 cylinders on idle, on boost though it does for sure (still with the boost spike issue of course)

Signs of possible vacuume leak somwhere id say, but really can`t find any god damn it ...
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post #5 of 6 Old 12-04-2010, 05:37 AM Thread Starter
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Quote:
Originally Posted by pzr2874 View Post
No CEL... very weird as it should hold/store the code.

My guess is the solenoid as well. Do you have access to a 3port BCS there and another tune ?
Yes and no, can order the 3port BCS no problem over here, but finding someone who can tune it is a real issue over here since its a ### car ... would have to go to the UK again
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post #6 of 6 Old 12-06-2010, 06:54 AM
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Quote:
Originally Posted by Hachigo View Post
I noticed that when turning the ignition/engine off, it takes a sec longer now until it really shuts off, it also sounds like the engine is not running constantly on 4 cylinders on idle, on boost though it does for sure (still with the boost spike issue of course)

Signs of possible vacuume leak somwhere id say, but really can`t find any god damn it ...
Wonder if a coilpack and or one of the plugs is shot?

Had an issue years ago (similar to this) and found a coilpack that took a dump (Just not sure if it actually is the issue because you might have a CEL)

Paul
2002 WRX Sold
2007 WRX Sold
2007 STi totaled
2007 Foz XT sold
2007 MS3
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