410 replies to this topic

[LukeFranky]

I have been a long time reader of suby club but this my first post.

Here's my story: I have a Subaru B4, 3GEN. I bought this car with a siezed primary turbo. Replaced both the O2 and O2/air flow sensor early to get rid of an error code I had. The car ran but no boost until the secordary kicked in. I replaced both turbos with similar but different turbos from some type of legacy.

After this I started to get a system too lean code uphill on the highway. Thought it was an air leak but couldn't find one. There was no misfire to begin with but eventually the problem got worse.

Before I could fix the problem the new primary turbo blew apart. I got sold a dud. Somehow the engine survived the shrapnel it had to eat and I rebuilt my old primary turbo and reinstalled it.

The car was running rough from all the oil it had been choking on. Replaced the plugs and coil packs. Cleared it up but the system too lean code was still there and misfire has only been getting worse.

I have replaced my injectors. No change. It's been almost 6 months now that I've had the problem and it has gradually got worse. The car thinks it is running lean but the black smoke and soot coming out of my exhaust says otherwise. It is clearly running rich.

The problem is worst at wide open throttle in mid revs. This is when the primary turbo boosts the most. I have found the problem is hardly noticable around town but gets worse with more highway driving. Closed vs open loop I guess. If you thrash the car it hesitates but once you get into the higher revs with an open throttle she starts accelerating better.

Most recently I unplugged the MAF sensor and the problem went away. However, if you give the car a good thrashing sometimes it will be accelerating hard then throw you forward in the seat with a sudden power loss. Not sure if that is just a consquence of unplugging the MAF or a deeper issue.

I just got an after market MAF which made the car run even more richly. So bad in fact it is difficult to get over 60km. I've unplugged it again for now.

I should note that the primary turbo boosts to about 17 psi. I thought this might be too much but nothing I've read confirms this. The secondary turbo which is still non-stock boosts up to about 16psi

I'm now at wits end. I love the car but had a gutfull. This isn't the only problem I've got. The clutch has a shudder and there is a noise in the manual gearbox, probably transfer bearings.

I'm pulling it apart today to the clean the O2 sensors. I'm very doubtful this will help because they are both fairly new.

Anybody have any clue what is going on? To recap: The car thinks it is running lean but it is actually running rich to the point it misfires.

[RX25SE]

Dont try to clean the O2 sensors, it will do nothing and you risk damaging them.

[LukeFranky]

I cannot actually remember the actual code now. Once I put the car back together I'll scan it again after a test drive. The battery was disconnected.

My old man who is a mechanic recommended cleaning them since the car had oil burn through the exhaust when the turbo blew.

I've checked the vac line setup quite a while ago, but I'll do it again.

[RX25SE]

I train mechanics on engine management systems and I don't recommend it.

[Jimbo]

To me it sounds MAf related or the car isn't happy with the replacement O2 sensors.

[LukeFranky]

I think I just found the problem. An air leak. I had previously checked for air leaks thoroughly, or at least I thought I had.

[Jimbo]

Where abouts?

[LukeFranky]

Any idea where to get that part of the intake that lives beneath the manifold? Gonna be a big job to get that out and replace.
Jimbo, right near the primary turbo.

[LukeFranky]

Yeah. That's the one. I'm trying out some RapidFix for now but I'd like to get my hands on a replacement part. Where are you located?
2002 MY03 3GEN

[duncanm]

upgrade time?

silicone intake

Symptoms certainly sound like a MAF problem or post-MAF pre-turbo air leak.

Have you looked at the O2 signal when warmed up and idling - should be bouncing on and off, indicating closed-loop A/F targets are being met.

I'd suggest just taping over the suspected leak before pulling the manifold - that's if you can get to it!

[Jimbo]

Do it once, do it right. Get a silicone intake tract, you will kick yourself if you don't!

$57 shipping from China? SWEET JESUS

[duncanm]

Yes - do it right. Tape was a suggestion for diagnosis only.
 
Same seller has this one $20 cheaper.

[Jimbo]

Increase the airflow!

[LukeFranky]

Well after fixing the air leak the problem was almost non-existent...almost. I had to switch back to the old MAF as the new one is a piece of rubbish.


However, it is now bogging down at high boost on primary again. It clears up when the secondary kicks in so I guess the air leak has opened up near the primary again. It is nowhere near as bad as before and the car feels a lot smoother at lower boost/throttle.

I think I will take your advice and purchase the silicone intake. Thanks guys.

Next job: transfer bearing...

[LukeFranky]

Hmm. Silicone intake would cost around $240 AUD. Is it really worth the upgrade since I can get a replacement secondhand relatively cheaply?

[Jimbo]

Well, imagine not having to pull the manifold off with all the other shit, for a second time. This is because you will probably snap the brittle fittings on the second hand unit trying to install it.

Happens errytime.

$240 well spent.