Up and down boost under same throttle accel.

Radial GT1 · Post by **Radial GT1** » Fri Dec 22, 2006 8:31 pm

Car. 93 4eat

Under normal driving acceleration I can actually watch the boost go up and down from 4 psi to 6 psi and after about 20 seconds of that it will jump up to full boost and back down again. It is kinda bothersome. If i really hop on it to the point the power light turns on the boost seems to hold steady and 8-9 psi. But I don't like to do that all the time for obvious reasons.

Could it be the silonoid giving me problems? I have no CEL's. I have searched for this and haven't found anyone with the same problems. Thanks for reading.

Bheinen74 · Post by **Bheinen74** » Wed Jan 03, 2007 4:33 am

check the connections of the boost gauge, sounds like you are leaking somewhere, probably have old loose hoses in there somewhere under the hood, most likely at a "T" connector, and they need to be nice and tight all over to read boost correctly.

Radial GT1 · Post by **Radial GT1** » Tue Jan 23, 2007 11:30 pm

True but the power goes up and down even if the turbo is showing constant pressure. It is not the boost going up and down that concerns me, it is the lack of power.

Boost will be steady and it will feel like I am driving with no boost at all. And than all of a sudden it (ECU) will change something and bam it has power, all with the nearly same boost reading. I can hear the turbo all spooled up and working. Somethin' is screwy.

92ss satinsvoice · Post by **92ss satinsvoice** » Sun Feb 04, 2007 3:07 am

sounds like your cars running rich. or really lean.

is your maf senser workin properly?

Radial GT1 · Post by **Radial GT1** » Tue Feb 06, 2007 4:10 am

I don't know. How would I check? It gets 18 er so MPG in town which sounds about normal.

The boost problem seems to have gotten worse with this cold weather. On a long up hill pull to boost varies from 4psi to 11 psi without my foot moving the throttle, and it does that up and down boost the whole time. It is not just my gauge giving the wrong information, I can hear the turbo changing speed, and the power jumps up and down too. What do you think?

bmxkelowna · Post by **bmxkelowna** » Tue Feb 06, 2007 4:16 am

o2 sensor?

Radial GT1 · Post by **Radial GT1** » Tue Feb 06, 2007 4:17 am

Still stock. Wouldn't those parts throw a check engine light??

edit: The car has 92K on it

Bosco · Post by **Bosco** » Fri Feb 09, 2007 2:50 am

TPS
Mine used to fuck with me like that on my first turbo legacy.
I had no boost gage, but the car surged all over like that.

I changed out the whole throttle body on mine which seemed much easier than installing and calibrating a new TPS.

....worked for me.

Radial GT1 · Post by **Radial GT1** » Sat Feb 10, 2007 4:14 pm

That sounds like my problem. Yesterday I was looking at houses for about 2 hours. Driving through city streets at low speeds. And when I would push on the gas lightly to go slow, it would stall a little bit, a couple times it actually died. This is an auto here it should not be dieing. The check engine light also came on for like a minute and then turned off. TPS, I'm going to subaru monday to get one. I'll give it a shot.

Radial GT1 · Post by **Radial GT1** » Sun Mar 04, 2007 2:58 am

I am in Iraq right now with the air force. I was too busy to get a TPS sensor before I left.

Does anyone have a Throttle body that I could buy from them to change in when I get home?

93forestpearl · Post by **93forestpearl** » Sun Mar 04, 2007 9:25 am

Got one in the cities. Lemme know when you're back.

Radial GT1 · Post by **Radial GT1** » Wed May 30, 2007 10:45 pm

Ok,

Update here.

I picked up a known good used TPS, and installed it yesterday. It from what I can tell did nothing. I checked voltage from pins 1 and 3 and it is a bit better than the old one was as far as being close to the numbers it should be. The swap did fix the initial stumble the engine had when getting on and off the gas at slow speeds. It did also fix the idle a little bit, but it is also rainy so it could just be the change of weather that is making it run a little different.

Same problems though. Low power in the boost unless I can over half throttle and giving it hell. Boost going from 5-8 psi on its own with my foot at the same position on the throttle. What other sensors will cause this kind of funk-ness?

Brat4by4 · Post by **Brat4by4** » Thu May 31, 2007 2:56 pm

Knock sensor. Have you updated to the revised knock sensor, old one would get cracks in it. The ECU might be logging a lot of knock counts and holding back the boost because of it, there is a span where the knock count can be high enough to pull boost but not high enough to trigger the CEL. (I have seen this many times on my car)

Did you ever read that stored code the car threw? If knock sensor is any of them, then you need to get the updated one.

Radial GT1 · Post by **Radial GT1** » Fri Jun 01, 2007 1:09 am

I had a CEL for the knock sensor when I bought the car a year ago, and replaced it with a new one from subaru. I just cleared the codes just in case it would do anything. Nope, same deal. Although I did have a TPS and a idle position code that was fixxed by changing out the TB. Codes are all gone now, all clear.

Boost still goes up and down, and boosting at 1/4 throttle is worthless, I think it gets slower in boost if I am not driving it hard.

Arctic Assassian · Post by **Arctic Assassian** » Fri Jun 01, 2007 4:20 am

What kind of BOV are you using? A leaking one could cause boost spikes right? It seems like you are loosing a large ammount of unmetered air.

Radial GT1 · Post by **Radial GT1** » Sun Jun 03, 2007 8:31 pm

It is stock, Do they have a tendency to fail? I will pull it off and check, that is something I didn't think to check.

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Up and down boost under same throttle accel.

Up and down boost under same throttle accel.