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Old 10-15-2003, 05:00 AM   #1
AMike
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2004 wrx

Default Bucking on new '04 WRX?

Is it normal for a WRX to feel like it cuts the fuel off (hard buck) between 4.5-5krpm when I lift off the throttle? I'm not snapping off, just lifting for a fairly leisurely shift. It doesn't do that in any other rpm band. If I lift very slowly it will smooth out, but there seems to be a definite blip in the throttle mapping or something. The car also seems to surge when the boost is coming on (2.5-3krpm) at >1/2 throttle. I don't live particularly close to a dealer, so I thought I'd ask here first.

The cloth seats are also looking pretty worn already - kind of sad.

I followed the 1k mi break-in procedure exactly - broke 4krpm once when I passed a truck, so I don't think that's the problem...
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Old 10-15-2003, 05:46 AM   #2
loreley
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Default

what gear is this happening in?

if its first/second, its normal, thats what you want a manual car to do anyways when you lift off the gas, stop accelerating. it will feel like bucking if you do it too quickly.

also, what is "surge"?
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Old 10-15-2003, 06:38 AM   #3
NateSD
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Not sure if it is normal, but I have this same problem when blasting down the mountain roads. Only have had it happen in second gear at the same RPM range when accelerating out of a corner and lifting off for the next. It is irritating though because it does "buck" pretty hard sometimes. I've just altered my driving still a little to compensate for this problem. Let me know if you figure something out.
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Old 10-15-2003, 06:53 AM   #4
AMike
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This happens in second and third gears. As I said, it only happens between 4.5-5krpm, otherwise I would assume I am just lifting off too fast. My last car, a BMW, did not buck unless I came off the gas too fast, and with the WRX I can pull off the gas fairly quickly at say 6krpm without any problems... I think I've even heard the tires chirp once when this bucking occured, and I was purposefully seeing how slowly I needed to lift to reduce the bucking.

Surging is when the acceleration is not constant. Think of it as lighter bucking.

NateSD, it sounds like you have the exact problem I have- very very annoying on mountain roads, which are found in abundance around here.
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Old 10-15-2003, 10:59 AM   #5
Unabomber
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I am 96.3% sure this is normal. My car does it too. From what I read, it is the wastegate snapping shut. At 4-5 krpm, you should be at boost and when you lift your foot off the pedal, the wastegate on the turbo snaps shut. This in effect creates a "wall" for all the exhaust gases and your car will buck. I might be wrong, but I am pretty sure this is correct. Try a search, or repost your question in the 2.0 forum in a few days for probably better assistance.
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Old 10-15-2003, 01:54 PM   #6
DrBiggly
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Do you have a manual boost controller? It can cause some unnecessary roughness issues exactly like what you are describing. Is the car absolutely stock?
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Old 10-15-2003, 02:05 PM   #7
AMike
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It is most definitely bone stock...

The feeling is like the faulty air flow meter in my old BMW ( or could it be a vacuum leak?)
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Old 10-15-2003, 08:36 PM   #8
jin psu
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I've noticed this on my car too. Today after work I was testing the waters after reading this thread. A couple of times it bucked real hard when I let off the throttle at high RPMs in 3rd gear. I'm not even lifting that fast but it seems like anytime I'm at WOT above 4k and lift all (or almost all) I get bucking. It's starting to scare me... anyone know if this has any negative effects on the car?

Justin.
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Old 10-15-2003, 09:14 PM   #9
jin psu
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Would a BOV relieve this pressure and effectively relieve the bucking?

Just a thought (so no anti bov flames ).

Justin.
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Old 10-15-2003, 11:29 PM   #10
AMike
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Well, it's good to know I'm not alone with the problem. It kind of sounds to me that Subaru might have released a bad ECU map or something. As far as being caused by the wastegate slamming shut, doesn't the WRX have a diverter valve? I mean, it can never shut off the exhaust flow completely, just divert it to or away from the turbo? Even if the wastgate slammed shut, wouldn't you just see a boost spike? Kind of new to turbo cars though...
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Old 10-16-2003, 01:32 AM   #11
razorlab
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My car has this problem as well. It also has hesitation and pinging from 3k to 5k then at 5k all power is back.

I took it to the dealer today and they could not find any problem with it even after I took a tech for a test drive. (of course)

I am going to take it to another dealer and see if they can find something out. If not, I am going to get it dynoed and get the paper graphs to show the hesitation/knock to SOA and tell them to fix my brand new car.
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Old 10-16-2003, 05:36 AM   #12
ImportVenom
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Hey guys, I had the same problem but got it fixed. If you are getting bucking without completely letting off the gas, then it's most likely a bad MAS sensor. It felt like the fuel would cut off when just backing off the gas (but not completely letting go of the gas) at 4500-5000 rpms. Get your MAS sensor replcaed by your dealer. If they don't believe you, ask to drive another wrx to prove to them it's not normal. This is only true if you're not completely letting go of the gas though and it's a serious bucking.
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Old 10-16-2003, 12:29 PM   #13
AMike
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Thanks for the reply. This is exactly what I'm feeling (forgot to mention that it happens only partially letting off the gas). The bucking was enough to make my wife scream once - she thought we hit something. I'll get it checked out at the dealer.
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