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Old 10-26-2010, 01:34 PM   #1
MTL_SLVR_WRX
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Default Hesitation at wot from 4000+ rpm

Last week I noticed that my ej205 2002 wrx was hesitating when flooring the throttle above 4k.

Driving above 4k with partial throttle is fine in all gears.
I'm able to reach target boost at wot.

I've already cleaned the maf sensor and throttle body...still the same problem.

I'm thinking it's the fuel filter, spark plugs, injectors, fuel pump, or ignition coils.

Is there a way to test if any of these is the problem, more specifically, the fuel pump, or ignition coils?
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Old 11-15-2010, 01:27 AM   #2
rex n effect
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bump...
wondering the same things.
new fuel filter and plugs already installed, though.
and only nearing 4k rpm
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Old 11-15-2010, 10:16 AM   #3
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I would guess your coil packs could be going out or are Alreaady bad
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Old 11-15-2010, 01:53 PM   #4
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seems to be a common problem with our engines. you can do a lot of little stuff to help smooth it out, but the stock map is just crappy. get a Cobb access port and flash it to stage 1, it will get rid of the hichups, smooth out the engine a TON, free up a lot of power you're missing out on and give you a much nicer power curve.
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Old 11-15-2010, 03:12 PM   #5
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Quote:
Originally Posted by Locky1138 View Post
seems to be a common problem with our engines. you can do a lot of little stuff to help smooth it out, but the stock map is just crappy. get a Cobb access port and flash it to stage 1, it will get rid of the hichups, smooth out the engine a TON, free up a lot of power you're missing out on and give you a much nicer power curve.
this shouldn't be the case for me...perhaps the person who replied to my original post.

I have a an 18G ewg, protune, etc...so I'm not running a stock map:
http://forums.nasioc.com/forums/showthread.php?t=2037129


I only noticed the problem a few weeks ago...might be the spark plugs, coil packs, or injectors.
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Old 11-15-2010, 06:39 PM   #6
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I had the same issue, hesitation under wot. Thread should be somewhere here. Regardless, first thing I would check is the clutch. If the clutch is fine, my hesitation was coming from a tear in the turbo inlet. I would check all of the intake tubing after the MAF. As well as vacuum leaks.
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Old 11-24-2010, 02:24 PM   #7
rex n effect
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mine was a dirty MAF
cleaned it with maf cleaner. doused it and sprayed it some more inside and out
all better
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Old 11-24-2010, 04:44 PM   #8
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Quote:
Originally Posted by MTL_SLVR_WRX View Post
this shouldn't be the case for me...perhaps the person who replied to my original post.

I have a an 18G ewg, protune, etc...so I'm not running a stock map:
http://forums.nasioc.com/forums/showthread.php?t=2037129


I only noticed the problem a few weeks ago...might be the spark plugs, coil packs, or injectors.
I have the same setup as you...what boost controller are you using?
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Old 11-24-2010, 08:53 PM   #9
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why in gods name would he check the clutch if he was having misfires? lol try boost leak tester, check coil packs, check cam and crank position sensors or maek sure your engine is timed properly with a light.it might have jumped time. also if his car was runnign fine on this tune reflashing to another tune would do absolutly nothing..except maybe make the problem worse
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Old 04-24-2011, 03:19 PM   #10
MTL_SLVR_WRX
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Default Update:

Problem is still happening.

Items I've already tried:
- cleaned the maf sensor and throttle body
- changed the fuel filter, spark plugs, knock sensor, front and rear O2 sensors


Here is my log.
https://spreadsheets.google.com/spre...AK&hl=en#gid=0


I brought it to my mechanic and said that it's not the ignition coils because I don't have any CEL's. A faulty coil pack would cause a misfire and throw a CEL. Target boost (19.8 psi) is not met. It maxes out about 1 psi less at the manifold. I don't think it's a boost leak because the afr seem to be ok. He thinks it might be that the spring in my external wastegate is too weak. Wastegate duty cycle only hits 16.86%. Could the fuel pump be dying?

Thoughts?
Any help would be appreciated.

Last edited by MTL_SLVR_WRX; 04-24-2011 at 03:34 PM.
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Old 04-26-2011, 11:25 AM   #11
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anyone?
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Old 04-26-2011, 12:45 PM   #12
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Does it do it from 4k-redline or just 4k-5k or what? I don't know what you're tuned to as far as AFR, but that stock sensor tends to read pretty rich under WOT, and it's showing high 11's on your log. That makes me think you're actually in the 12's. I would look to a fueling issue. A longer log might help as well.
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Old 04-26-2011, 02:33 PM   #13
MTL_SLVR_WRX
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It happens starting from 4k all the way to redline.
Basically, when there's load and boost builds up and the wastegate opens.
Partial throttle all the way to redline is no problem.

The log only shows until 5K because I didn't want to prolong the issue since it sounds and feels really bad when I floor the accelerator.
Something is definitely wrong and I don't want to make the problem worse if I don't have to.

Concerning the fueling issue, do you think it could be the fuel pump?
I already changed the fuel filter.
What about the possibility of an intake or exhaust leak?
What do the AFR's from the log tell you?
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Old 04-26-2011, 03:43 PM   #14
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various other threads on this board have suggested that the O2 sensors cause this when they go bad, with a lot of confirmations of this from other users. i'd check/replace those asap.
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Old 04-26-2011, 03:47 PM   #15
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Quote:
Originally Posted by Locky1138 View Post
various other threads on this board have suggested that the O2 sensors cause this when they go bad, with a lot of confirmations of this from other users. i'd check/replace those asap.
I did!

Quote:
Originally Posted by MTL_SLVR_WRX View Post
Problem is still happening.

Items I've already tried:
- cleaned the maf sensor and throttle body
- changed the fuel filter, spark plugs, knock sensor, front and rear Bosch OEM O2 sensors


Here is my log.
https://spreadsheets.google.com/spre...AK&hl=en#gid=0


I brought it to my mechanic and said that it's not the ignition coils because I don't have any CEL's. A faulty coil pack would cause a misfire and throw a CEL. Target boost (19.8 psi) is not met. It maxes out about 1 psi less at the manifold. I don't think it's a boost leak because the afr seem to be ok. He thinks it might be that the spring in my external wastegate is too weak. Wastegate duty cycle only hits 16.86%. Could the fuel pump be dying?

Thoughts?
Any help would be appreciated.
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Old 04-26-2011, 03:59 PM   #16
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IAM and feedback knock are fine while punching it and the boost builds up quick and then stays there. Numbers wise Im not seeing where your boost is hesitating or fluctuating. Even your load is responding well to the throttle.

I suspect the high AFRs because you're pro tuned to run 11.5:1. Am I missing something?

edit: nm 1psi less boost. can you take a screenshot with learning view and post it?

Last edited by wrxBRAH; 04-26-2011 at 04:08 PM.
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Old 04-26-2011, 04:07 PM   #17
MTL_SLVR_WRX
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Thanks for chiming in guys...

I can't tell you either...I was hoping someone could spot something I couldn't.
Boost isn't hesitating or fluctuating, but acceleration is.
Almost as if timing is being retarded because of knock, but that doesn't seem to be the case.

What can be determined by the wastegate duty cycle only hitting 16.86% ?
Could hesitation be due to a faulty coil pack without throwing a CEL?
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Old 04-27-2011, 08:55 AM   #18
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couple of things pop out at me from the log:

in particular look carefully at line 11
  • we are still solidly at 100% throttle
  • engine speed is steadily increasing
  • engine LOAD has taken a dip. we can see the source of this from the MAF g/s going 181 189 183 202. there is no GOOD reason why the mass air flow would dip like that.

that leads me to the MAF sensor itself. one of the best tests you can do with a MAF sensor is to temporarily swap it with another known good one.

the wastegate/boost issue is a red herring. you've got plenty of MAP.

400ms/line is a bit too slow for a good log, btw. cut out a/f sens 1, feedback kc, fine learning, all of the MRPs but (direct). the two knock correction columns are irrelevant if IAM can be verified at 16. in fact, as long as you know IAM is 16, you don't even need to log it.

that will get you much faster logging, probably in the sub 200ms range, which can catch some things a log at 400ms will not.
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Old 04-27-2011, 12:01 PM   #19
MTL_SLVR_WRX
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Thanks for your input.
I'll try to see if I can get my hands on a good MAF sensor and test it out.

Will post new a log with fewer columns to get a quicker interval between rows.

Any idea why the wastegate duty cycle is only hitting 16.86% ?
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Old 04-27-2011, 02:04 PM   #20
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well, it may be that WGDC doesn't need to be higher.

remember boost targets are not MRP, they are MAP. depending on atmosphere, altitude, you may be already hitting the targets?
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Old 05-02-2011, 04:23 PM   #21
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Default problem solved.

Compression test done.
Pleasantly surprised that the result was 160 psi on all four cylinders.
So that wasn't the problem.

Anyways, I went to my mechanic and borrowed some coil packs he had laying around. He told me that if a coil pack fails, the engine will misfire and will throw a CEL. Since this didn't happen, he doubted it was the problem.

My tuner, Mike from Innovative Tuning, told me that it's not necessarily the case, and coils won't throw a CEL until they stop firing completely. Turned out he was right.

Car is running great now.

Thanks to all for your input.
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Old 11-20-2013, 08:32 PM   #22
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I'm going to bump this thread as I'm noticing roughly the same kind of thing happening in my '05 WRX. WOT and right around 5K RPM the car starts to shudder and hesitate a bit.

HOWEVER, I was testing it out today because I thought it was all in my head. I ran it up to 5K again and same thing. I did one more pull to 5K and this time I heard RATTLING sound that seemed to come from the left side of the engine bay (though I can't totally be sure because I was too busy freaking out wondering what I broke). I don't seem to have broken anything.

Notes about the car:
- It has the STI exhaust and DP on it.
- No other engine modifications (to my knowledge)
- I always run 92 octane as instructed
- I do currently have a CEL with a P0546 code which I'm being lazy about fixing

Any other info I can provide. I'm not sure what to make of the recommendations everyone made above since I don't have quite as many mods as the OP.

Thanks in advance!
-c

Last edited by soundsinsilence; 11-20-2013 at 08:34 PM. Reason: Adjusting info
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Old 11-21-2013, 10:30 AM   #23
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i think im having the same kind of issue soundsinsilence. mine seems to happen between 4-5k rpms. getting that rattling sound between half throttle and WOT.
only mods are aftermarket drop in filter and up pipe.
could it be coil packs goin bad? i have no cels.
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Old 12-29-2017, 06:55 PM   #24
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Quote:
Originally Posted by soundsinsilence View Post
I'm going to bump this thread as I'm noticing roughly the same kind of thing happening in my '05 WRX. WOT and right around 5K RPM the car starts to shudder and hesitate a bit.

HOWEVER, I was testing it out today because I thought it was all in my head. I ran it up to 5K again and same thing. I did one more pull to 5K and this time I heard RATTLING sound that seemed to come from the left side of the engine bay (though I can't totally be sure because I was too busy freaking out wondering what I broke). I don't seem to have broken anything.

Notes about the car:
- It has the STI exhaust and DP on it.
- No other engine modifications (to my knowledge)
- I always run 92 octane as instructed
- I do currently have a CEL with a P0546 code which I'm being lazy about fixing

Any other info I can provide. I'm not sure what to make of the recommendations everyone made above since I don't have quite as many mods as the OP.

Thanks in advance!
-c
Ever figure it out?
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Old 06-26-2019, 03:25 AM   #25
Elver231
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Quote:
Originally Posted by MTL_SLVR_WRX View Post
Thanks for chiming in guys...

I can't tell you either...I was hoping someone could spot something I couldn't.
Boost isn't hesitating or fluctuating, but acceleration is.
Almost as if timing is being retarded because of knock, but that doesn't seem to be the case.

What can be determined by the wastegate duty cycle only hitting 16.86% ?
Could hesitation be due to a faulty coil pack without throwing a CEL?
I run a Subaru Legacy 95 N/A and has exactly same problem. So, it is not turbo or something you mentioned, because my car I replaced everything to brand new. What I thing is it happens if ECU misunderstand 4 to 5k as it was red line and cuts fuel just for a moment, when you don't floor accelerator, you can keep speed or increase it, but hesitating do not occurs. Suggestion, we have to cheat on ECU in order to correct this issue and make it never cut gas, no matters rpm you are running.
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