Jerking at high boost - Subaru WRX Forum
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#1 Old 02-21-2011, 08:14 PM
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Jerking at high boost

Like the title says there is jerking at high boost. When I get up around 8 or 9 pounds it feels like I lose all boost for a second then it come back then it jerks, feels like there is tons of hesitation not normal at all.!Cry!
02 WRX
stage 2 cobb tune
catless up and down pipe
invidia n1
cobb sf intake
Can anyone help or tell me whats going on.
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#2 Old 02-22-2011, 05:38 AM
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It's a boostleak. You need to look at a 3port with a protune <-- helps in the longrun

Clean your MAF while you are tightening up the TMIC y-pipe and such. Is that the old SF intake of COBBs' ? You have an aftermarket downpipe, right ?

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#3 Old 02-22-2011, 08:32 AM
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the sf intake is less then a year old and yes I have an aftermarket catless downpipe with the cobb flash dont have the money for protune but will get one soon
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#4 Old 02-22-2011, 11:25 AM
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Check your TMIC connections and your intake. Reset your ECU (disconnect the battery and step on the brake for a few seconds to drain the system) and reconnect it after 30 mins.

Any CEL.

Paul
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#5 Old 02-22-2011, 11:35 AM
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No none and everything looks good on the data log. If it was a boost leak why did it continue to boost to 13 after it felt like the power was back?
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#6 Old 02-22-2011, 12:28 PM
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Not a clue, without a CEL... it's a guessing and evaluate game.

edit:

Wait, you never said it was hitting 13psi. Look into replacing the stock bcs or get a 3port.

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#7 Old 02-22-2011, 01:33 PM
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13 PSI on a Cobb OTS map? Isnt that a bit on the low side ever for stage 2?

Joshua
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
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#8 Old 02-22-2011, 01:45 PM
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Are you reading this from the AP or from a gauge ?

Get yur mods together in your profile sometime... I remember you installing a gauge at one point.

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#9 Old 02-22-2011, 03:41 PM
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I was reading it on both gauge and ap and yes it is low but I let off after I felt that and I didn't reach full boost

Edit: sorry for leaving that important fact out
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#10 Old 02-23-2011, 05:38 AM
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Sounds like fuel cut. Wonder why there isn't a CEL

What was peak boost before all this ?

Paul
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#11 Old 02-24-2011, 02:51 PM
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15.5ish psi
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#12 Old 02-24-2011, 03:25 PM
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15.5psi is a decent number. It really sounds like a boost or fuel cut-off. I was having the same issue with mine. Ended up being a fuel cut-off issue. But my problem is coupled with a boost leak.

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#13 Old 02-24-2011, 10:02 PM
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I really don't know what. It is or was but now it just feels like the car has lost power but still hiting good boost and everything is good and no cels
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#14 Old 02-25-2011, 12:32 AM
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Compression check it. I feel like I've seen a bunch of people talking about this now, and I wish I had saved the trouble, spent the 3 hours to pull the plugs and checked the compression. I thought mine wasn't boosting, but when I'd check the numbers (after an ECU reset) I would still be pulling 16-17 psi, which was normal for the tune I had. It would feel like a misfire between 25-3000 rpm, but then it would smooth out and it just felt like I wasn't getting full boost anymore. Try taking off your oil filler cap when the car is warmed up, and look for it to be puffing white smoke. If you rev it, you'll see it blow out smoke like your breath on a cold morning. Well, you'll see that if you've got a piston/ringland problem. If you do see that, check your compression and see what cylinder(s) is(are) the offending one(s). My compression when the block was cold read 120, 119, 123, and 61. If you DON'T see puffs of white smoke at idle, nor smoke when you rev it with the filler neck open, move to the bottom of this post.

I hope that I'm wrong, and that it's something related to your ignition or front A/F (O2) sensor, and not a mechanical failure. Check the oil filler neck and move from there. I wasted almost a month waiting for Subaru to not figure it out, when I spent a few hours and found out the horrible news myself. I wish I would have just diagnosed it myself in the first place.

Other possible causes as I understand would be spark plugs, coil packs, or front A/F sensor.

PS: My car also would do a learning cycle and start pulling the boost so it would max out around 10 psi over the course of a couple hundred miles or so. Never once threw a CEL.

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#15 Old 02-25-2011, 05:41 AM
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^^ Good point on the plugs. Didn't think about that.

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