Wierd boosting senario!!

[stipro]

Ok, last week I was driving with full boost, stock engine, around 9 psi. Then for no aparent reason, I could only get 5, maybe 6 psi. The boost gauge told me so, a definate decrease in power. After letting the car sit for the weekend, I drove it to work this morning, full boost. Driving home tonight, 5-6psi. What gives? Could it be a faulty solenoid? I dont have a mbc, so I cant really try adjusting it. Any comments will help. Thanks in advance.

[ultrasonic]

You might search around, but I think that's the symptom for a bad boost control solenoid. The 5 or 6 psi is what you get with only the waste gate spring controlling boost.

[LaureltheQueen]

If i remember correctly, syphon had this same problem.

[dzx]

my guage reads 5 when the hose slips off the boost control solenoid but i doubt thats your problem. Probably what they suggested. Bad solenoid

[free5ty1e]

did you (or anyone else perhaps) put regular or mid-grade gasoline in your car recently? That is also a symptom of the ECU realizing that you are not running premium, and limiting boost. Fill up with premium and get octane booster to counteract the regular or midgrade and you should be fine if that's it...

[stipro]

ummm..... Good thought but I always use premium fuel

[argossy]

replace your knock sensor, just did the same to mine, i was getting exactly the same symptoms... when your ecu thinks your engines knocking it retards timing and limits boost among other things... and your ecu wont register a fault until the sensor eventually craps out fully... so try that good luck.

[Calgaryturbo]

I had the same problem. Get a MBC it is way better!

[TurboLegacy]

i get full boost in first gear, then i only get 5 psi in every other gear. could this be my knock sensor also?

[chochocho]

i am only about to hit boost to 3psi. knock sensor? boost solenoid?

[BXSS]

did you (or anyone else perhaps) put regular or mid-grade gasoline in your car recently? That is also a symptom of the ECU realizing that you are not running premium, and limiting boost. Fill up with premium and get octane booster to counteract the regular or midgrade and you should be fine if that's it...

+1

My car did this when I first got it due to regular gas & a cracked knock sensor.
I put in some premium & changed the knock sensor & 8.7 psi was back!

[BXSS]

i am only about to hit boost to 3psi. knock sensor? boost solenoid?

That sounds VERY weird.

Do you have any CELS?
When my knock sensor was bad I had about 4 codes stored in the ECU, but swapping out the cracked knock sensor killed all of them...

It sounds like a bad boost solenoid to me as you are not even getting actuator pressure.

If you do not have any CELs try connecting the pressure signal (3/16" fitting on the turbo's compressor outlet) directly to the actuator.
This should give you about 8-9PSI as you are on a 16G.

[BXSS]

If anyone is getting just actuator pressure rather than full stock boost & is on Premium gas do a visual inspection of the knock sensor for cracks.
The crack(s) will be very obvious with the knock sensor still mounted on the car.

I checked the knock sensor on my wife's 2.2l Impreza this past Sun & noticed it was cracked so I pulled one out of the garage & swapped it onto her car - took about 5 minutes to do.

Be CAREFUL with the harness wire as it is OLD & fragile!

I actually used the newer knock sensor off a PII Subaru motor on the SS & my wifes car by just swapping the new style connector for the old style connector (no cutting - repinning sort-of).
Practice getting the connector off on the old broken k-sensor you'll need a pic to unlock the pin from the connector.

When I examined the k-sensor of the wife's car I noticed the insulation in the wire going to the k-sensor was eaten through by rubbing on the block I assume.
I'm planning on using a piece of wire loom/cover stuff to keep this from happening again.