Hi all, so lets start with the basics.

I have a stock 06 WRX Type UK, with the only mod being a K&N panel filter.

Recently, it started to occasionally 'misfire' under load, like it skips a beat. This is really intermittent, but is getting worse when it does actually do it. It does it whilst cold and warm irrespective of weather conditions.

Now, it doesn't like to rev past 4k revs, and feels like its not boosting, and will then rocket off like its just dumped a shot of NoS into it! I'm not getting a CEL, so I wouldn't imagine that it's stored any codes. Also, from tickover, if I rev to 2k and hold, it'll surge, but on tickover it's shaky, like the ICV is dirty. I also swear I heard it pinking at one point.

The MAF is relatively new (1k miles, dealer part replacement), and the 3rd party dealer I bought it from claimed to have serviced it (I have my doubts), and it has just flown through an MOT.

I'm no stranger to the dirty end of a spanner, but this one has got me beat. So before I go insert my ignition key up the dealers nose with extreme velocity (car is still under warranty), can anyone help me with the most likely cause?

After many many searches, I've come up with the possible:
1. Knock sensor
2. Coolant Temp Sensor
3. Clogged fuel filter
4. Plugs
5. Neutral position switch (this is a new one to me!)
6. Dirty MAF (oil from the K&N)
7. Coil pack breaking down
8. Vacuum leak

I doubt it's mechanical, due to it being intermittent, but I'm not ruling it out

Can anyone think of anything I've missed? Anyone else had this same problem?

 

Don't bother with guess work mate, go see a specialist and get it fixed. Everything is repairable...

Must be a load of tuners in your neck of the woods....

Anyone care to point him in the right direction???

 

Thanks matey. The car is still under warranty, but I want to know the exact problem so when I speak to the dealer, I want to be able to tell them *exactly* what to fix, as I don't want them taking it to bits to diagnose it, as I trust them about as much as I trust a kid with an ant and a magnifying glass!!

One of the guys on here has offered a health check, and Scoobyclinic isn't far, but I don't want to be spending money that I don't need to if you get me?

If it's not one of the issues I mentioned, then it'll be compression test time. If it fails miserably on a compression test, then I may get the dealer to pay for a replacement engine. This place has put me through enough as it is, and a quick trip to Trading Standards would set them straight I'm sure!

 

As i was reading your post my first thought was coil pack causing it to miss, the description of shakey idle and hesitance when coming on boost.
But then i got to,
6. Dirty MAF (oil from the K&N)

Have you oiled the panel filter? If so, that would be my first port of call. Clean the MAF and fit a new dry filter in and try it before going any further.

 

The filter is brand new, but they're still oiled, so there's a (remote) chance that could be causing it!

I shall give it a clean later and will let you know.

Anyone else got any thoughts here?

Thanks! M

 

The plot thickens:

This morning I started car, and as always let it sit for a minute (until the temp gauge starts to move) before setting off. Despite the fact it was hunting slightly on tick over, it wasn't missing. I pulled off and commenced my journey to work.

All the way in, the car never skipped a beat. Pulled firmly through the rev range, and boosted properly. This is, until; I got into work. I pulled up, and on tick over the car started missing slightly. So I revved to 2k, and it was surging again, and sounded like it was pinking (This is, of course; a guess, as I don't know 100% what scoob that's detonating sounds like, but basing it on how non Boxer engines sound, it was very similar).

I've been working on NA cars for years, and have never had such an intermittent fault.

So I have 2 options here.
1. Drive over to ScoobyClinic
2. Drive back to the Dealers.

As these are in opposite directions, I need to make my decision today. I'm not convinced that the Dealers know what they are doing with Scoobs, so I'm thinking it's going to be a trip to Chesterfield.

If anyone has had this issue before and has managed to solve it without a remap please let me know!

Thanks. M

 

Hunting on tickover, remove and clean the idle control valve, make sure u seat the rubber ring correctly when fitting it again,

 

Thanks Tomwrx, It only hunts on tick over when cold, which lead me to believe that the Coolant temp sensor is playing a part here. I'll give it clean as a matter of course next service, provided I can get the damn car to run properly!

Cheers, M.

 

UPDATE: So JDM_Stig has had my hawk plugged in and data logged, and it seems as though I have a duff CTS.

Will get this swapped out ASAP, and we'll see if it improves!

I'll update this thread when I have more information!

Cheers
Martin.

 

Looking forward to see if you get this fixed as mine had a similar issue but almost seems as if its cured itself.

 

Well I've got all the data out of a power run after the ECU was reset mate, and the only thing playing funny buggers was the coolant temp sensor.

Maybe you need to get yours data logged and see what it comes out with?

Makes interesting reading, that's for sure! The rear lambda was reading a bit odd, but I put that down to the CTS being off. It was reading 97 degrees, when the dash was reading about 85 and a thermometer on the thermostat housing was reading about 80. As a result the ECU will be running incorrect fuel levels.

Hopefully should have it sorted soon and will re-log everything.

 

For anyone interested, or stumbling across this from a search, the coolant temp sensor has made a massive difference in running. A lot smoother and power all the way through the rev range.

Hopefully this has fixed it... We'll see in a few days and will post back if its fixed it fully or not!

 

Yes please keep me updated. Mine has been running okay since a change in oil. I've also had the throttle body off to clean it. It also had a mew MAF but didnt make much difference. The thing I notice is that using the learning view software it's leaning out the fuel in the long term learning all across the rev range.

Mine did seem to be much worse in warmer weather.

 

For anyone following this thread:

The poor running/jerking/hesitation when cold has disappeared now, although I have a poor idle when cold, and a shake on tickover when warm. Although it's pulling like a train on and off boost!

Next step will be an IACV clean (when I get round to ordering the gasket).

If that doesn't fix it, then the car is going in under warranty in case it's head gasket/ring landing related!

 

Glad my Diagnosis worked

 

The plot thickens further.

The shake and 2k splutter is back!

As the car is still under warranty I'll be speaking to the dealer in due course, as I've spoken to Area 52 Autosport, and it seems the best course of action here is Dyno diagnostics, this is something the dealer I bought from cannot do.

Will update more when I've spoken to the dealer and area 52!

 

head gasket failure............

 

Man you're obsessed!

Having said that, its quite possible, although that's not a problem to me, as the cars under warranty still, and so it'll be fixed!

On a side note, "pumping up" the brake on tickover almost kills it, and the car drops right down on revs.

Romraider is showing 2 misfire counts each on cylinders 1 & 4, which may well give someone an idea?

RECAP: This is what's happening now:

From cold start, car revs up to 1500 revs and waivers until the temp needle starts moving.

Car then drives fine until warm.

When fully warm and sat on tickover it shakes and occasionally splutters. Holding the car static at 2k revs produces what is like a misfire (no misfires triggered on romraider at this stage). Pumping the brake pedal on tickover causes an almost stall and a waiver in the revs there after for a few seconds whilst it settles. Left on tickover for 5 minutes or so causes misfire counts on cylinders 1 and 4.

Still no CEL/EML or codes stored.

That is all!

Updates to follow.

 

Still following this thread. Looking forward to the conclusion.

 

It's actually a bit random. I've filled up with VPower today, and it's behaved ever since...

Starting to think this may be pump related!!!

Proper random! Lol

 

MAF.

 

New genuine Subaru part... Although it wouldn't be the first time I've got a duff part.

Will give it a clean tomorrow anyway!!

 

And change to a none oiled filter, oem Sti, or green cotton, avoid piper cross.

 

haha, mine was a bit random. an ecu update fixes it for a few tank fulls.

But ever since I changed the oil to shell helix 5w-30 is been running mint.

How high is your oil level?

 

Oh, and have you cleaned your throttle body?

 

What fuel do you normally run on?

 

Ok, to answer some shizzle:

Oil changed 2 weeks ago, level is a gnats nad below max

Oiled filter was blotted off before fitting, but feedback taken on board, I'll chuck a paper one in and see if it makes a difference.

Not looked at the throttle body, but fair point, I'll give it a clean.

Only ever VPower or momentum... It's a 2.5, on anything less it'll det like mad, explode into a fiery ball, and open up a worm hole to DS9!!

(Think I got all of the question answered there)

Cheers guys, appreciate the suggestions!!

 

So; I discovered an exhaust blow the other day, which I fixed, and since then the car has been leak-down and compression tested by Scooby clinic and all is good figure-wise.

Funnily enough, after the car was put back together and ECU reset, it's all come right!!!

I'm assuming something was loose, or a plug wasn't torqued up. Either way, it's all good now! Power is back, and it's smooth as a baby's bum!

 

aye up mate, where was your exhaust blowing? Need to check all mine as it seems slightly louder than before but no "normal" blowing sound on tick over.

 

Mine was cat to centre section. The metal donut is really worn, but it's the original exhaust, so it's hardly surprising. A good test is to get underneath, find any soot deposits on the outside, clean them off the exhaust and re-check after a week. That should show you where it's leaking, if indeed it is!

Mine was loud on WOT, but otherwise you wouldn't know. Got under, cleaned the centre to cat connection and ran it for a while, the soot deposits were evident after a couple of weeks.

Good luck!

Cheers