97 Legacy TT Boost Problem?

[Flunk]

Howdy, new member here, first Subaru I have owned, and first post on these forums, so first of all I apologize if I screw something up.

I have spent the last hour or so looking around for information regarding my problem, but have not found too much relevant.

First if all, I have a fairly bog standard 1997 Legacy GT TT, No mods that I'm aware of other than an aftermarket BOV that I installed.

I have purchased a boost guage, however not got around to installing yet as I have not had the time to find a pressurised line to T it off.

My problem is this:

Driving around under 4000rpm is fine, feels like it boost well, turbo sounds healthy, BOV functions correctly.

If I decide to push it and wind over 4000rpm, it feels like the boost just cuts out completely, like I have throttled back to sit at 4000, when in fact my foot is on the floor.

At the same time, I have also noticed my fuel pump is making quite a loud droning sound, when the car is idling it is very easy to hear.

As I am new to Subaru's, I wondered if they have a boost cut for lack of fuel, if the fuel pump is the cause of the problem?

Or if the loud fuel pump is common?

Would like to get a few opinions before I fit a new fuel pump if it is not required.

[neodowd]

Does the second turbo kick in at around 4500 rpm? If so its normal vod its when primary turbo de spools before secondary kicks in.

[Flunk]

Negative, If i keep the boot up it, It still feels like there is 0 boost, VERY low acceleration, I have to keep reminding myself that this problem is there, otherwise it catches me out when overtaking.

I have dismantled the fuel pump, still making an Odd noise, however it is not the standard fuel pump, so previous owner must have upgraded, explaining the noise.

Even after a long drive, secondary turbo is cool or luke warm, suggesting that it is not engaging at all?

I guess I need to find out how to install my boost guage to be 100% sure.

In the last few days my CEL has been staying on constantly when engine running also.

[neodowd]

Yea, first thing would be to install the boost gauge to see if the secondary turbo is actually boosting at all. If its not boosting could be buggered. Have a check of all your vac lines are attached and not cracked and if you have any codes logged.

[Jord]

If your secondary downpipe is not hot after a few quick 4000+ rpm pulls then it would indicate your Exhaust Control Valve (ECV) under the secondary turbo is not opening giving you no secondary boost. The CEL code logged on the ECU will probably just be a code 66 it would pay to check out which code it is anyway. There are several reasons that could cause the ECV to not open.

Are all the vacuum lines in the correct place with no cracks or splits in them?

Can you hear any vacuum leaks while the car is idling?

What octane fuel do you run it on?

[Nick_96_RSB]

Thread on CEL codes & what they mean, http://www.clubsub.org.nz/forum/index.php/topic,67.0.html

Connect 2 small black plugs under dash ( behind drivers side kick panel) & turn ign on - dont start car. will spit out a code long flashes = 10. short flashes = 1, i used my video camera on my phone to record it so i could sit down with a piece of paper and work out the codes it was throwing. that will at least give you an idea of what is going on & eliminate them as part of your problem

you would certainly know if you were on the "secondary" as once the VOD runs out you'll get a kick in the pants and be hauling ass again

has it ever run both turbos at once since youve owned it? or just a new issue?

PS: my boost gauge is run off the vac line between intake manifold & BOV - back through the hole in firewall on drivers side, wiring i cant help with as was all done for me by a fellow club member

[Flunk]

 Jord said:

Are all the vacuum lines in the correct place with no cracks or splits in them?

Can you hear any vacuum leaks while the car is idling?

What octane fuel do you run it on?

As far as i can tell they are fine, i replaced quite a few of them when i brought the car.

Cant hear any obvious leaks.

BP 98.

[Jord]

Ok good well using 98 should rule out the ECU safeguard to stop detonation. Have you checked the codes yet? While you've got your head under the dash plug together the black connectors and green connectors then turn the ign to on.Quickly go pop the bonnet and you should here a clicking noise coming from the drivers side strut tower in the engine bay, this is the ECU checking all the solenoids that control the secondary turbo. You should also see the actuator rod on the secondary turbo move up and down as well as the valve on the underside of the intercooler. Note the will only do it 2-3 times before the vacuum in the storage tank runs out so you need to go look as soon as you turn the turn the key.

If these you actuators dont move at all you have a problem with either the vaccum plumbing or the solenoid box (BBOD)

Also as Nick said, is this a new problem or was it like this when you bought it?

[Flunk]

 Jord said:

Also as Nick said, is this a new problem or was it like this when you bought it?

I have only owned the car for about 3 monthes.

After purchase i sent the thing into Submarine Spares in ChCh for a full service, got belts and tensioners etc changed, just to be safe as previous owner couldnt tell me when it was done.

Have been having problems with it ever since, and the people at submarine spares irritate the pee out of me with their responses, so have decided to try figure out the problem for myself rather than paying them any more money.

Will get into it this afternoon and find out what the fault codes are.

[Jord]

Yeah things like this can end up costing a fair bit at a mechanic if they arent educated on how the system works. Once you understand how it works its not that bad, just takes time isolating the problem.

Which vac lines did you replace when you bought the car? Did you replace them one at a time? You may have just put one of the lines in the wrong spot. Thats all it would take to throw the system off.

[Flunk]

I dont recall exactly which ones i replaced, but im 100% sure i replaced them 1 at a time, exactly where they came from.

I have also followed your instructions Jord and can confirm the actuator on secondary turbo is functioning.

Update: I have tried following the CEL instructions, and if i am doing it correctly i am recieving the following codes:

22

22 Knock Sensor Abnormal voltage emitted Sets regular fuel map, retards ignition by 5degrees

23

23 Mass air flow sensor (AFM) Abnormal voltage emitted Fuel map set by revs and throttle

65

65 Differential pressure sensor

So, my next 2 questions are obvious.

Could these codes be screwing with how the turbos operate?

And how do I go about repairing said codes?

[Nick_96_RSB]

you didnt change any of the vac lines that had restrictor pills in them did you? if you did i would be putting them back on, i believe they have a white band or line on them to identify them

23 is your AFM, possibly needs changing - just bedind air intake box, there is a sticker on the square bit of it which will tell you what colour you need will be on the side facing the firewall - can go from anywhere between $50 & $150 for a second hand one

22 is possibly your knock sensor needs to be changed, & 65 again not sure but also might be a sensor that needs changing

[Jord]

65 differential pressure sensor. This sensor is mounted on the firewall connected to hose #21 and #22. It measures the difference between the primary boost and secondary boost. This is quite possibly your problem, they dont normally fail but its possible. Try plugging the green and black plugs together like I said earlier and then turn car on and take it for a short drive at 11km/h+ . This resets the ECU and will wipe the codes if they are no longer a problem, if the ECU is still finding a problem the code(s) will remain.

Im not sure if the other two codes will effect boost control but you should get them looked at ASAP as you dont want your engine leaning out and melting a piston or destroying a BEB.

[Flunk]

Thanks for the info, is there any way i can test it myself?

Or is the only option to replace and see what happens?

[Flunk]

UPDATE:

Problem solved.

Went for a drive with plugs in, AFM & Knock codes disappeared, so only active problem was 65.

Stopped, checked the sensor, it wasnt plugged in properly.

Plugged it in, cleared the codes.

CEL is now off, can car boosting properly.

THANK YOU! I never would have known how to check the codes, or find that sensor without your info.

[Nick_96_RSB]

Nice one dude! congrats!

[Jord]

Nice one. Yeah theres often old codes stored on the ECU that are longer causing problems so it always pays to wipe ECU before you start poking around! Happy to help