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2007 WRX 2.5 hesitation at low rpm


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Hi

Since buying my wrx it's had a hesitation at low rpm before boost.It's a little worse when cold but always there regardless.

It does this anytime i'm below 3k rpm once passed that it usually revs through pretty clean.

So i changed the plugs and no difference. Changed the knock sensor as the light come on for that not long after changing plugs.Still no different.

Done a compression test and got 110 psi on all 4 cylinders which i'm assuming is ok ?

Any ideas what else i should check ?

 

Car is an 07 2.5 wrx (hawkeye) only mod is cat back ninja 2 exhaust everything else is standard, 56k miles with full subaru service history. No knocks or rattles no smoke and no leaks.

 

Thanks

Dave

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They suffer badly with it mate, I had it on mine, I googled the cra p out of it and it's almost accepted that  a lot of Hawks just do this, I changed loads of stuff chasing mine but in the end got a remap and that got rid of that particular problem

was your comp test with a cold engine

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I've never heard that as a general rule hawks hesitate. We have two local members and I've never heard them complain if the same symptoms you have.

Did you have it code read when the light came on? Could be a misfire caused by a faulty lead.

How extensive have you been with your search for air leaks? I'd suggest sticking it on a rolling road and have the Afr and knock checked.

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I did air leaks religiously, and then found more so treble checked.... And found more.... Cable tied and clipped everything, thing is as these age the pipes harden and then leak a little tiny bit, but there are so many pipes on the engine that can leak and make up a rather impressive total leak, barring any holes splits or popped off pipes of course

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Nope, fixed air leaks didn't stop mine, nor did knock sensor, o2 sensor, maf, plugs, throttle body, electric throttle pedal, air filter etc 

like I say, I had months of it and I trawled the net for months, 

its a sign in ringland damage, it's a sign of bad avcs, bad plugs or gaps, fuel pressure problems etc etc, but the more I trawled the more a certain thing popped up and that was the transition of closed and open loop being a big factor due to the tune, and from what I can remember mappers I think were changing something to do with that 

altho as usual, you only have the people with a problem posting up mostly so don't really mean it's a hawk thing I suppose ? As 8 out of 10 hawk owners might not have it

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On 9/30/2016 at 5:30 PM, Piggysniffer said:

They suffer badly with it mate, I had it on mine, I googled the cra p out of it and it's almost accepted that  a lot of Hawks just do this, I changed loads of stuff chasing mine but in the end got a remap and that got rid of that particular problem

was your comp test with a cold engine

Thanks for the reply...

Yeah i've read a lot and no one ever seems to fix it. I don't want to go wasting money on parts unless i know for sure there no good.

Yep comp test was from stone cold.

23 hours ago, Scoobyghost said:

I've never heard that as a general rule hawks hesitate. We have two local members and I've never heard them complain if the same symptoms you have.

Did you have it code read when the light came on? Could be a misfire caused by a faulty lead.

How extensive have you been with your search for air leaks? I'd suggest sticking it on a rolling road and have the Afr and knock checked.

When i first bought the car (6 months ago) it had this fault and cel light and was diagnosed by dealer as secondary air system so they replaced all that at big ££ still no different but no more cel.

Then i found the intake pipe to turbo had been split by the jubilee clip so dealer replaced that and still no good. So the dealer then sent the car to some subaru god on the scottish boarders and they diagnosed it as bad plugs. So i got car back to find it still have similar fault just a bit different (worse). 

Then cel light came back on pointing to the knock sensor so replaced that, still no different.

so i thought i'd change plugs myself (to be sure) and found the subaru god had fitted the shorter plugs from the 2.0 wrx haha. I did the compression test at the same time as fitting correct plugs but now im back to the original problem...

there is a strange noise before it gets boost like an air fluttering? noise. It sounds as though wastegate is opening and closing then once it hits boost the sound goes away and engine runs great? The hesitation as within the same rpm range as the noise.

 

Btw it's been to 2 different main subaru dealers and the scottish guy and nothing was mentioned about the noise so it could be normal ? My old classic wrx never did it.

 

By air leaks do you mean in the boost system or vac ? i've visually inspected both and all seems good. Boost hits 13psi as it should...

 

Thanks for the replies

 

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I have got a noise like that when mine starts pulling timing as it comes on boost, the only way I can describe it is it sounds like something moving/spinning is touching something else very slightly and it sounds like it's happening inside a tube, I know that sounds odd, but that's how it sounds to me, it may be that the noise is a product of the timing having been pulled tho, and not a reason for it, it's odd tho

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3 hours ago, Piggysniffer said:

I have got a noise like that when mine starts pulling timing as it comes on boost, the only way I can describe it is it sounds like something moving/spinning is touching something else very slightly and it sounds like it's happening inside a tube, I know that sounds odd, but that's how it sounds to me, it may be that the noise is a product of the timing having been pulled tho, and not a reason for it, it's odd tho

Could be similar. I have got a video somewhere of the noise i'll post it up if i find it..

3 hours ago, Piggysniffer said:

I did also read that if your secondary air pump seizes up it can create so much load on the ecu that it can actually damage it and cause running problems

Wouldnt there be a cel light on for that ? Any other way of knowing ?

I've had to take the car off the road now as i'm worried it's causing more damage driving it with the fault so any suggestions of things worth testing would be greatly appreciated.

I know a remap would probably fix it but that's £500 i don't have :(

 

Thanks

Dave

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I didn't have a cel when mine was seized, but my ecu kept resetting itself every couple of days, yours could be waste gate flutter, that's another thing that will cause hesitation coming on boost as its trying to set the pressure but can't as its flapping open and shut, you can adjust the length of the waste gate arm to put a little more load on the Spring and if it is flutter due to spring fatigue that should sort it

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You can check wether the pumps working on a cold start by listening to it, it should sound like a Hoover for about 30-45 seconds and then the secondary air system solenoids should close and the Hoover noise should get louder for a few seconds as it builds pressure and then it should stop blowing/turn off, when this is done you can then disconnect the rubber pipe that feeds the secondary system from the snail of the pump while the car is running to make sure the solenoids have shut and that there is no exhaust gasses blowing back through the system (not good)

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12 hours ago, Piggysniffer said:

I didn't have a cel when mine was seized, but my ecu kept resetting itself every couple of days, yours could be waste gate flutter, that's another thing that will cause hesitation coming on boost as its trying to set the pressure but can't as its flapping open and shut, you can adjust the length of the waste gate arm to put a little more load on the Spring and if it is flutter due to spring fatigue that should sort it

I'm convinced it's wastegate flutter but could be worng. I've read a few horror stories about adjusting the wastegate arm is there a guide somewhere on how it should be done?

Could it be checked using diagnostics on live data to make sure it is that ?

I noticed a few weeks ago when i was looking at the wastegate that the arm was quite loose, i was able to move it fairly easy ?(engine off) but not with engine on..(edit) Just checked again and i can't move it with engine off lol so ignore this bit haha.

12 hours ago, Piggysniffer said:

You can check wether the pumps working on a cold start by listening to it, it should sound like a Hoover for about 30-45 seconds and then the secondary air system solenoids should close and the Hoover noise should get louder for a few seconds as it builds pressure and then it should stop blowing/turn off, when this is done you can then disconnect the rubber pipe that feeds the secondary system from the snail of the pump while the car is running to make sure the solenoids have shut and that there is no exhaust gasses blowing back through the system (not good)

Yeah the secondary air system seems to be working fine, stan palmer (subaru carlisle) replaced the pump and the 2 selanoids (£2k) so im sure it's all good but i will check that anyway.

 

Thanks for taking the time i do appreciate it...

Dave

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If you have a boost gauge it may show up as fluctuating boost as it does it, really is an easy job to do the waste gate arm, the ball ache is taking the turbo shield off which is a pain on its own, but you also have to take off the intercooler (I think) to get at it, I suppose the other thing it could possibly be is the boost solenoid and restrictor pill, maybe both could do with a clean with electrical contact cleaner, there's stuff on google for the doing of above operations, basically just connect your green connectors together under you dash/steering wheel/foot pedal area once you've removed solenoid, taken pipes off (remembering which goes top/bottom, with the connectors connected and ignition on the car will start cycling the fans and that solenoid will continuously open and shut, while its doing that you buzz the cleaner through it, and restrictor pill is in pipe coming from turbo snail (I think) and pipe needs to be removed and cleaner squirted down there to clean the pill/brass restrictor

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