how do I check if stock boost control is working ok?

That spinning thing that makes all of the cool noises. OE and Aftermarket.

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czo79
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how do I check if stock boost control is working ok?

Post by czo79 »

Hello all...
I have been having some problems with my turbo...and it may actually be two problems, its hard to tell. One is that when driving at very low throttle, cruising, between say 75-90, I occasionally get this hiccup...where it sorta just feels like the engine cuts or kinda stumbles for a split second, then goes back on it way. The other thing is generally at or near full throttle, high boost at high rpms, there is something causing the car to jerk real bad, I think it often tends to happen when I lift throttle a bit...it feels like the car is getting full boost and then its gone and the drive train gets unloaded and then bam its back (the boost) a split second later and the drive trains loaded and your going...
Its kinda hard to explain all this well, its kinda hard to even figure it out myself. Anyways, I did my plugs and they looked ok and then I thought it made the stumble at cruising better, but it started again pretty quick, so it may have just been luck.
Anyways, is there a way I can check the functioning of the stock boost solenoid? I've heard on older cars they can have problems...
thanks
Micum
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Post by -K- »

My car does much the same thing, I'm sure some of it is the driveline components are all old and loose. But some of it is the engine. I have a boost gauge and it didn't move at all when this happened so I don't think it's the boost controler. I'm not running the boost controler any more, I have a bleeder, with no change. So I'm prettysure it is a bit of the cursed HESITATION.
02 WRX Sedan, 5mt
93 Sport Sedan, 5mt
czo79
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Post by czo79 »

I'm almost positive neither of the problems I am expierencing is due to hesitation...this is much more drastic...more violent...
thanks
Micum
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91 Legacy Turbo Sport - 94 JDM EJ20G
97 Legacy 2.5 GT - mod'd
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vrg3
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Post by vrg3 »

Micum, do you have a boost gauge? If so, what happens on it when this happens?

You could always try bypassing the stock boost control and just running wastegate boost. If the problem goes away, get a manual boost controller (in another thread I describe how I made one for like 4 bucks) and cap off the stock solenoid.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
czo79
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Post by czo79 »

thanks Vrg3...
thats the info I was looking for. I though I could check it by doing something like that. I don't have a boost gauge, really need to get one. But I need quite a few gauges really...and I want electrical ones. And it all seems like such a pain to install. So I am thinking I want to get the defi link setup, because you can install the link control unit under the hood, and then you only have to run one set of wires through the firewall, because it conencts with a daisy chain system. Seems like the extra price is justified by the ease of install, so I can tackle it myself. And all the cool functions...but it of course makes me put it off cause of the price.
Oh yeah...so its the wastegate control solenoid that I want to disconnect to check this? Leave it attached to the ECU, but disconnect the vacuum hoses and cap them?
thanks
Micum
Micum
91 Legacy Turbo Sport - 94 JDM EJ20G
97 Legacy 2.5 GT - mod'd
93 Impreza L AWD (sold)
97 Legacy 2.5 GT (deceased)
98 Legacy Outback (sold)
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Post by vrg3 »

Woah! No, don't just disconnect the hoses! That'll give you maximum boost!

The solenoid has three hoses going to it. One from the turbo's compressor outlet, one from the wastegate actuator, and one from the intake resonator box. If I recall correctly, these are, respectively, the upper nipple on the side, the lower nipple on the side, and the nipple on the bottom of the solenoid.

Take the first two off the solenoid and connect them together with a vacuum fitting. Put caps on the nipples of the solenoid.

This will bypass the boost control and connect the wastegate actuator directly to the compressor outlet. You should see around 5 or 6 psi.

Oh, and if you're rich enough to be able to afford those Defi gauges, I think you can afford to get a simple mechanical boost gauge to use in the meantime. You can get one from an eBay auction for like 20 or 30 bucks. Stick a tee in the line by the pressure exchange solenoid and run the vacuum line through your firewall, and that's it. You don't even have to power the gauge if you can do without illumination. It'll be very good to know what your engine's intake manifold is seeing.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
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Post by mikec »

If anyone knows of the test procedure for the boost controller, I'd like to see it as well. I've got a boost gauge hooked up finally, and while I'm seeing 17-20 inHg at idle, I'm only getting 6-7 psi of boost.

I've got the gauge tapped in the line from the intake manifold before the T, which helped the idle reading a bit compared to where I had it before (after the T). Don't think it should matter in this situation, but I'm using the crappy hard line that came with the gauge.
"That shouldn't be a problem, since I do regularly visit the realm of subatmospheric manifold pressures." -- vrg3
91White-T
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Post by 91White-T »

6-7psi sounds right.
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Brat4by4
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Post by Brat4by4 »

Sounds like you are running wastegate boost. Is there a check engine light on? If you haven't checked the codes, do that soon.
1993 WMP BC6 5MT EJ22T 9psi 3.9:1 213k 205/55R16

62.6 m/s @ 0.66 bar. Gotta love boost. :)
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Post by mikec »

Nope, no CEL right now... I'll go out and see if there's any stored codes right now.

Back! Got a 23 - Airflow Sensor. Hrm... Guess I'll reset the ECU and see what happens.
"That shouldn't be a problem, since I do regularly visit the realm of subatmospheric manifold pressures." -- vrg3
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Post by mikec »

I had to do the drive it around with the green and black connectors attached, because leaving the battery unplugged didn't clear the airflow sensor error. While driving, I got a 32 - Oxygen sensor inoperative. :x

Any chance this is because I just reset the ECU the other way? What have I gotten myself into? 6-7 psi wasn't that bad, afterall.

Edit: Checked the stored codes again, and still, airflow meter, but thats it. ARGH!! No CEL while driving normally, and I think still only 6-7 psi of boost. Fark it... The car runs, and the lower boost will probably keep me from killing myself. Plus I don't have money to chase down electrical gremlins. Although I did notice a smell once I parked the car. Any idea what the difference is between an oxygen sensor for a turbo and an NA car is?
"That shouldn't be a problem, since I do regularly visit the realm of subatmospheric manifold pressures." -- vrg3
legacy92ej22t
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Post by legacy92ej22t »

I have 3 codes that won't clear off my computer either. IIRC 23,24,49. IAC, and both MAF codes. I did a D-check and got the 32 O2 sensor only. Replaced the O2 sensor and I got the all clear in D-check mode but still get the 3 codes in read mode. :? I replaced my MAF and I still get the 3 codes in read mode and I've reset my computer a whole lot of times. I haven't tried anything with the IAC valve so I hope when I address that they'll finaly clear. I have been told by a couple different mechanics to have my ECU/ECM checked though too after explaining these events to them.
The O2 sensors are the same on the turbos and N/As' IIRC, 4 wire.
-Matt

'92 SS 5mt. All go and no show. Sold :(
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Post by Jarvis »

These symptoms are EXACTLY what I had when we discovered one tiny vacuum tube ever-so-slightly loose, not off, just loose. Give those little things an extra lookover and I'll bet you find one loose, maybe cracked.

Jim
www.thepearsonhome.com/subaru_legacy.htm
mikec
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Post by mikec »

Who's symptoms? I just realized this thread kinda got hijacked. Sorry Micum!

I have started replacing mine, but the hose I've got so far doesn't go on as tight as I would like. Does anyone know the stock vacuum size? I thought 1/8th.

And yeah, back to the original thread, if anyone knows how to check the solenoid, I wouldn't mind giving that a go as well.
"That shouldn't be a problem, since I do regularly visit the realm of subatmospheric manifold pressures." -- vrg3
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Post by mikec »

Okay guys, I'm gonna give this thing one more go... So if anyone can think of any reason why spraying brake cleaner into the side nipples on the stock boost controller would be a bad thing, lemme know quick! I want to see if its become stuck or something.
"That shouldn't be a problem, since I do regularly visit the realm of subatmospheric manifold pressures." -- vrg3
ciper
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Post by ciper »

Why brake cleaner? Carb cleaner is cheap.
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Post by mikec »

I've already got brake cleaner.
"That shouldn't be a problem, since I do regularly visit the realm of subatmospheric manifold pressures." -- vrg3
91scoobiesubie
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Post by 91scoobiesubie »

does the octane of your gas have to deal with boost? reason why im asking you say your getting 6-7 psi, if iput 87 gas in my boost gauge reads 5-6psi but 93 always gives me 9-10 psi. if gas has nothing to do with it whats wrong with my car?
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Post by mikec »

I'm using 92, so that can't be it. Good idea tho, I wish that was it! :?
"That shouldn't be a problem, since I do regularly visit the realm of subatmospheric manifold pressures." -- vrg3
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Post by mikec »

I'm gonna resurrect this thread with a list of what I've tried so far:

Moved boost gauge to just after intake manifold, before the T that goes to the emmissions stuff.
Replaced the provided hard vacuum line with soft vacuum line, and a smaller and simpler T.
Tried cleaning out the stock boost controller (twice) with brake cleaner (clicked like crazy after the first spraying).
Cleared all the codes, and listened to the stock controller click away like crazy in the D check mode.
Replaced some (not all yet) of the stock vacuum lines that I can see.
Changed spark plugs and wires.

Still only getting 6 psi max. I'm wondering, could a 11-12 year old cat be the source of all my frustration? If its plugged enough, could it be hampering exhaust flow to the point where I can't get more boost?

Also, does anyone know how the stock boost controller is constructed? Is it possible its leaking, so while its working properly, air is getting by and activating the wastegate? I guess the only way to check that is to try another one.

I've got a Joe P MBC on the way. I'm also hoping its not the gauge reading off. I guess I'll see what happens when I install that. :x

Sorry for being slightly offtopic, and being kinda longwinded... But I want more boost!
"That shouldn't be a problem, since I do regularly visit the realm of subatmospheric manifold pressures." -- vrg3
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Post by legacy3kgt »

i am new to Legacy's, but in my experience with turbos, you usually can't get more boost than stock if you use your stock boost controller.

btw, I'm having the hickups too, and throttle position makes no difference after like 1/4 open, she eats gas wayyyy fast, and i have generally no power. I'ma try the wastegate boost thingy

which solenoid is it?????
I'ma just wing it, have had luck with that approach in the past.

gosh, I was gonna say/ask something else, but I forgot what it was :roll:
-->Andrew


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Post by DOA »

Same symptoms as me, scares me whitless when you can hear everything banging away. Did you manage to cure the original problem with the vacuum hoses as most of mine are what I would call loose.
Oh and the control solenoid is the one thats bolted to the front of the (i would guess over there) passenger side suspension turret (worked that 1 out with no assistance :P )
If only I hadnt bought the bike, this would feel fast :P
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Post by 91riored »

DOA wrote:Same symptoms as me, scares me whitless when you can hear everything banging away. Did you manage to cure the original problem with the vacuum hoses as most of mine are what I would call loose.
Oh and the control solenoid is the one thats bolted to the front of the (i would guess over there) passenger side suspension turret (worked that 1 out with no assistance :P )


i figured it out but like it turret ..would breaking of it cause overboosting?
i guess i'm the forum a-hole now
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