Bogging/idle chasing gc8 WRX

shuffbag · Post by **shuffbag** » Tue Mar 22, 2016 8:32 pm

I'm hitting a wall here guys, I have a standard gc8 except front mount intercooler and its run flawless for years... But what started as a hesitation has now developed in to idle chasing when at lights from almost stalling to 1000rpm. Struggling to come on boost or really anything over 3000rpm.

I've been reading about boost leaks and detected one by the turbo, so I replaced the intake with a silicone intake (prick of a job) It may still have one... I need to pressure test it this weekend.

Vacuum stays solid -20 at idle so I'm assuming no vac leaks from the manifold.

Is there anything else I should be looking at?

shuffbag · Post by **shuffbag** » Tue Mar 22, 2016 8:34 pm

It's a 98 model if that helps.
Not getting hot and no starting issues.
No codes either or warning light.

YouTube · Post by **El_Freddo** » Wed Mar 23, 2016 8:44 am

Leaking injector?

Have you done a compression check?

Idle air control valve operational/clean?

I'm beating around the bush on this one as I don't own a wrx or have much experience with them.

Another thought - AFM that's dirty or on the way out?

Cheers

Bennie

Post by **TOONGA** » Wed Mar 23, 2016 2:22 pm

As Bennie said IACV is the most likely culprit.

Does it have a factory exhaust ? I remember reading (USMB from memory) that the turbo downpipe is a catalytic converter (one of two) which can get blocked causing all sorts of issues. Don't know if this applies to your model or not.

TOONGA

shuffbag · Post by **shuffbag** » Wed Mar 23, 2016 3:01 pm

I've had a faulty/dirty afm in the past, completely different feeling.
The motor is strong so I don't think compression issue.

idle air controller might be something to look at.

Just pressure tested it again, found some more slight leaks. Nothing major, tightened the clamps.
We'll see if that fixes it...

shuffbag · Post by **shuffbag** » Wed Mar 23, 2016 3:02 pm

Has full factory exhaust, is there a way to tell if your cat is blocked?

stenno · Post by **stenno** » Thu Mar 24, 2016 5:11 am

Tps & / or oxygen sensor. Had same issue with my 98 wrx.
Ended up swapping on another throttle body, oxygen sensor from a GX liberty and reset the ecu, fixed it for me

shuffbag · Post by **shuffbag** » Thu Mar 24, 2016 9:36 am

Found a few more leaks, tightened seems alright atm.

Will check in if it faults again

Post by **TOONGA** » Thu Mar 24, 2016 6:18 pm

shuffbag wrote:Has full factory exhaust, is there a way to tell if your cat is blocked?

Two ways lack of power and symptoms similar to yours, the second way unbolt the cat and do a physical inspection

shuffbag wrote:Found a few more leaks, tightened seems alright atm.

Will check in if it faults again

Good to hear you may have solved the problem

TOONGA

shuffbag · Post by **shuffbag** » Sun Mar 27, 2016 8:52 pm

It's reoccurred again but not as bad, I tightened some intake hoses and replaced some vac lines. Gave me a slight bump on the vac gauge (in a good way).

It's almost like a stutter when initially coming on boost now. Do fuel pressure regulators in subarus fail? That's kind of the the feeling I get.

I also plunged the read plugs together when it was faulting, no code.

The cat is in the dump? So can't see it because of the bends?
Blocked cat would do it 100% of the time? Not intermittently?

It's doing my head in....

Post by **TOONGA** » Mon Mar 28, 2016 3:08 pm

A blocked cat should cause power problems all the time.

When you look at the factory dump pipe, if it has a cat in it, it will look like this image.

image stolen from here http://www.forum.wrx.com.au/viewtopic.php?t=81333

There may be another cat below that one as well. Or you may just have one cat at the bottom of the dump pipe, there are a few variations.

Regulators can fail, it could even be your fuel pump failing to deliver the right pressure.

TOONGA

shuffbag · Post by **shuffbag** » Tue Mar 29, 2016 4:52 am

Yeah so no checking the insides. Might need to get the fuel pressure gauge out

Nubaru · Post by **Nubaru** » Tue Mar 29, 2016 7:41 am

you can get some funny issues with leaking injector seals but if I recall rightly is more an idle issue. This is the seal thit fits on injector body and seals to intake manifold

shuffbag · Post by **shuffbag** » Mon Apr 04, 2016 7:06 pm

So I still have this issue.
I'm leaning towards o2 sensor. I went to the rear when it was idle chasing, it was really rich while hunting and the problem gets worse the warmer it gets. Is that a trate of a o2 sensor on the way out?

shuffbag · Post by **shuffbag** » Mon Apr 04, 2016 7:07 pm

Failing that I'm heading down the decat path...

FujiFan · Post by **FujiFan** » Wed Apr 06, 2016 3:56 am

Has full factory exhaust, is there a way to tell if your cat is blocked?

I recently had a health check on my 93 Liberty exhaust system. The mechanic removed the EGO sensor and used one of those flexible hose type cameras (like a bore-o-scope type hand held unit) to visually inspect the Cat converter on car. All good was his diagnosis. He also checked out the rear muffler, which apparently has rusted out baffles

explaining why the Lib has a bit of a tune to it!

J.

Post by **TOONGA** » Wed Apr 06, 2016 9:33 am

If you do go the de-cat path, get an aftermarket down pipe and keep the factory one if your car has to ever go over the pits.

Have you ever changed the O2 sensor? or is it the factory one? It is worth changing it if it is the original sensor.

Have you done an ECU reset ?

TOONGA

shuffbag · Post by **shuffbag** » Fri Apr 08, 2016 1:13 pm

ok so i have changed the o2 sensor, cleaned the IACV (dirty bugger) and the MAF. the car ran a bit smoother.

previously i've changed some vac lines and intake. i've pressure tested it and all good there.

its like its nice and smooth normal driving, but add some hard driving/boost (stagea pulled up next to me) and it idle hunts/stutters next time its stationary

and have new leads and plugs going in over the weekend.

YouTube · Post by **El_Freddo** » Fri Apr 08, 2016 9:56 pm

If new plugs and leads don't work I'd be looking at the injector seals as Nubaru has mentioned.

Cheers

Bennie

shuffbag · Post by **shuffbag** » Sat Apr 09, 2016 4:32 am

El_Freddo wrote:If new plugs and leads don't work I'd be looking at the injector seals as Nubaru has mentioned.

Cheers

Bennie

i was reading that the pressure test would show leaking injector seals?
pressurizing the whole intake and manifold.

plugs and leads will go in later today after work.

I'm thinking of plumbing in a fuel pressure gauge (under the hood), if the pumps on the way out it might be starving the engine of fuel after a bit of spirited driving? sound plausible?

and i know i could search it, but in simple terms whats the easiest way of doing a ecu reset? i may have been doing it wrong.