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Old 10-04-2010, 02:16 PM   #1
Scotty Dosent Know
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Default Hesitation and slight rough idle?

I have an 06 WRX wagon, the car has 75K miles on it and is all bone stock. Have only owned the car for about 4 months.

When sitting at a light etc. it does not feel like the car is idling smoothly it almost feels like there is a slight miss. It is not super rough or any thing but its enough that my fiance said some thing about it lol

Also when you go to get on it in lower rpms the car almost feels like it wants to bog or hesitate. It seems to be worse when the car is started and once its completely warmed up not so bad.


I cleaned the MAF the other day and was going to clean the IACV but now that I looked at the TB I dont believe 06 up has one? If you guys could give me a few things to check/clean/replace I would appreciate it since these car are new to me. The first thought that came to my head was plug wires......but then again lol
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Old 10-04-2010, 03:43 PM   #2
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I would check all of your vacuum lines to see if you have a leak going on. Pressure test the system and get a vacuum diagram for your car, this will help a lot! They can be found all over google/here. Any CEL's ever?

Will
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Old 10-04-2010, 05:19 PM   #3
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A good place to check is where the intake hose connects to the turbo inlet. This is a very commonly torn area, and my torn hose caused symptoms such as yours. I'd definitely say a vacuum leak of some sort would be the first thing to check for.

Edit: My car never threw a CEL in this case.
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Old 10-04-2010, 06:06 PM   #4
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I dont believe the car has ever had any CEL's I have only had the car for 3500 miles though. The previous owner had the car serviced at one place though and I have all the maintenance history from new and it has nothing about a CEL (we are the 2nd owners)

Maintenance records said that new spark plugs were installed at 60K but could a dirty MAF possibly lead to fouled plugs? I am wondering if I should toss a new set in for peace of mind.

I will have to start checking vacuum lines and also the turbo inlet. I helped a friend replace a turbo on his Legacy GT and his turbo inlet was in pretty bad shape so I also helped him install an aftermarket inlet (its basicly the same motor as a WRX isnt it??)

I have never done a pressure test can I do this my self or is the equipment expensive? Sorry for all the questions I have worked on a lot of cars just never a suby.
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Old 10-11-2010, 10:24 PM   #5
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I checked around (no vac test yet) for vacuum leaks and did not find any the other day. Car seemed to be running like usual the other day driving in seattle and I got on it to make a left turn yield and the car almost seemed to cut out a couple times kind of hitching and bucking through the intersection. Could this be a fuel filter issue?
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Old 10-12-2010, 04:46 PM   #6
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are yew puttin 92 octane gas in it???
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Old 10-12-2010, 05:13 PM   #7
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Does it get worse under load at all? I had a similar problem with my fiance's Jetta and if you basically did a brake stand it would hesitate very badly. It ended up being a bad coil pack.

Last edited by Rigged; 10-12-2010 at 05:25 PM.
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Old 10-12-2010, 09:20 PM   #8
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Quote:
Originally Posted by Uncle Scotty View Post
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are yew puttin 92 octane gas in it???
Yep always 92, im new to subys but its not my first rodeo haha

Quote:
Originally Posted by Rigged View Post
Does it get worse under load at all? I had a similar problem with my fiance's Jetta and if you basically did a brake stand it would hesitate very badly. It ended up being a bad coil pack.
I only get a slight bit of hesitation between 2-3K RPM right before boost nothing big but annoying and also my idle isnt perfect but more just a little blurb you can feel when sitting there and radio etc. is off and quiet.

It has done the bad cutting out on me once in first going around a corner and once to my fiance also in first going around a corner.

the fuel filter was changed it says at 30K in the paper work I have so I may try that first and also search for vacuum leaks a little harder.

if its not either of those maybe coil like you said I guess
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Old 10-12-2010, 11:49 PM   #9
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Quote:
Originally Posted by Scotty Dosent Know View Post
Yep always 92, im new to subys but its not my first rodeo haha



I only get a slight bit of hesitation between 2-3K RPM right before boost nothing big but annoying and also my idle isnt perfect but more just a little blurb you can feel when sitting there and radio etc. is off and quiet.

It has done the bad cutting out on me once in first going around a corner and once to my fiance also in first going around a corner.

the fuel filter was changed it says at 30K in the paper work I have so I may try that first and also search for vacuum leaks a little harder.

if its not either of those maybe coil like you said I guess

sounds like its running OK as far as the idle issue....my car has the subbie 'idle' thing.....most do....and you may want to check the fuel pressure for the cutting out and run some injector cleaner through it


maybe change fuel brands


fuel is a regional thing and some are better than others....and a 'good' gas brand here in florida(I have best results with Shell and Exxon)....may be a bad choice where you are


get some Techron gas treatement/injector cleaner and try that first
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Old 10-13-2010, 07:51 PM   #10
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there are alot of us with the same hesitation at the same rpm.some people have replaced parts and solve the problem but i fall into the group that after changing everything and being tuned still have the pulsating throttle between 2-3000 rpm. it seems to not do it as bad since its cooled off. something is making the car pull fuel in that range.
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Old 10-14-2010, 12:05 AM   #11
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i'm in the same boat as well (04 sti). I have tried a crapton of things, and still nothing has fixed it yet. There is a lot of things this could be, and some of them have already been covered. i think the wrx is less sensitive with vacuum/boost leaks than the sti, but you may have one or multiple ones. ziptie all of your vacuum hoses in your motor. why? some of the oem fittings dont' have barbs on them. when the hoses get old and dried out, they no longer seal as they should. ziptie the crap out of the connections and it will most likely help. it made a large improvement to my car. Other problems could be bad/clogged injector, improperly gapped/bad plugs, failing front o2 sensor, torn turbo inlet, crappy tune, bad maf, bad crank sensor, bad avcs oil screen, clogged fuel filter...the list goes on. try unplugging your mafs and drive around, if your car runs better, your mafs is bad. do the same for the front o2. make sure you reset your ecu each time. you'll probably have to go through a lot of tests and some parts swapping to get it cured. goodluck!
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Old 10-18-2010, 01:01 PM   #12
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Having an identical issue at 108k miles. Stock 06 Wagon. Keep me posted.
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Old 10-18-2010, 01:59 PM   #13
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Quote:
Originally Posted by Scotty Dosent Know
I have an 06 WRX wagon, the car has 75K miles on it and is all bone stock. Have only owned the car for about 4 months.

When sitting at a light etc. it does not feel like the car is idling smoothly it almost feels like there is a slight miss. It is not super rough or any thing but its enough that my fiance said some thing about it lol

Also when you go to get on it in lower rpms the car almost feels like it wants to bog or hesitate. It seems to be worse when the car is started and once its completely warmed up not so bad.

I cleaned the MAF the other day and was going to clean the IACV but now that I looked at the TB I dont believe 06 up has one? If you guys could give me a few things to check/clean/replace I would appreciate it since these car are new to me. The first thought that came to my head was plug wires......but then again lol
I have the same problem with my 05 outback xt limited so I pulled the coil packs and 3 out of the 4 were going bad, mine also did not throw a check engine. I am now looking for a set of new coil packs for mine. Good luck with yours.
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Old 10-18-2010, 05:43 PM   #14
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Thanks for the ideas guys, honestly I have been so busy that I havent even gotten a chance to try any thing more. I will post back again when I get a chance! Any more ideas stories etc that might help feel free to post
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Old 10-18-2010, 09:44 PM   #15
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I had a bad coil pack on cyl. 2. The clip holding it in snapped. New part coming in thursday. Zip tie in the meantime to hold it in place so I can limp around town.
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Old 11-03-2010, 02:09 AM   #16
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OK so I may be getting a little closer maybe to figuring this out lol


This weekend the car threw a code and the CEL came on, I went to the local parts store to borrow their code reader and it couldnt read the code

Well later that day the CEL went off. Then SUnday it came back on and went off later that day. Now that my fatherinlaws shop is open I cant get it to throw a code again WTF

Do these cars store codes in the ECU or do I have to wait till it comes on agan and drop every thing and go to the shop to use the scan tool? This car is pissing me off.

The hesitation is way worse when the car is cold BTW.......maybe O2?
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Old 11-03-2010, 04:40 AM   #17
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My 06 wrx had the same issues... Occurred after I missed a shift. I still think to this day It was due to a bent valve. Compression check was fine...

My symptoms were slight miss at idle. Car was pulling timing right around the 3k range only at partial throttle. The car would accelerate fine then hesitate in that range. WOT was fine. Def. worse when it was cold. The problem had nothing to do with gas or plugs. Never threw a cel.
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Old 11-03-2010, 10:10 AM   #18
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Quote:
Originally Posted by mcganz121 View Post
My 06 wrx had the same issues... Occurred after I missed a shift. I still think to this day It was due to a bent valve. Compression check was fine...

My symptoms were slight miss at idle. Car was pulling timing right around the 3k range only at partial throttle. The car would accelerate fine then hesitate in that range. WOT was fine. Def. worse when it was cold. The problem had nothing to do with gas or plugs. Never threw a cel.
I had the exact same symptoms on my 04 sti. Did you ever figure out what the problem was? Did you ever try a leak down test?
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Old 11-03-2010, 05:57 PM   #19
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I ended up selling the car because I was sick of trying to figure out what the problem was...

Forgot to mention the timing belt jumped a few teeth. Replaced the bad belt tensioner. Never did a leak down.
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Old 11-03-2010, 07:36 PM   #20
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could the timing belt be the cause maybe? my xt has close to 90 thouand miles so it will be due for a change anyway
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Old 11-03-2010, 09:34 PM   #21
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^^^ i believe it is a possibility. My 04 sti has 96k on the clock. My timing belt and tensionors look perfect and the timing has not jumped. It is definitely possible the timing belt is just worn down. Until I get a leak down test done (and some extra cash) I am not going to replace the timing belt. The local subie shop said they've seen weird crap go on even before 105k, but did not elaborate on it. I suppose even if the leak down test is bad, i'm still going to have to replace the timing belt and tensionors, so what the hell, i guess i should go ahead and do it so i can rule it out. hmm maybe the timing belt should be on our troubleshooting list.
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Old 11-03-2010, 10:15 PM   #22
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but wouldnt it do it throughout the entire rpm range if timing was off
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Old 11-04-2010, 02:21 AM   #23
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Yea my car is worse when it's cold and then a few times when it's warm it has done the cutting out/ bucking thing but just fir a sec then it's fine. I'm pretty sure it's a sensor and not a bent valve. The guy I bought the car from got it new and was older so it wasn't hot rodded
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Old 11-04-2010, 02:26 PM   #24
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I Have An 06 Wrx, Through A P-0303 Code. Its Tuned With Utec And Its Alwayed Hesitated Between 2-3000. Before The Utec It Didnt.

My Idle Started To Get Worse And Worse About A Month Ago. Last Weekend I Changed The Plugs And My Midpipe And Exhaust Gasket And It Went Away. Today I Felt The Hesitating Just A Little. I Feel Like Its Going To Come Back. My Next Step Is To Change Or Check The Timing Belt If It Jumped Some Teeth. It Burps At Idel As Well. Its A Fuel Problem I Beileve, If I Stop At A Light, I Can Smell The Exhaust Sometimes And It Smells Like Fuel Is Not Being Burned. The Spark Plugs Helped A Lot With The Smell, Hesitating And Not So Much The Burping At Idle
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Old 11-04-2010, 03:41 PM   #25
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Im Thinking Its The Front 02 Sensor Or Injectors! Not Sure If You Changed The 02 Sensor Yet. Im Going To Run Fuel Injector Cleaner Then Im Doing The Sensor Next And Will Post Later.
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