Sporatic boost.

[jaboc03]

I have been having a problem with the boost for the past month. I have a GT28 turbo (S15) on my redtop with basic goodies like 3 inch dp and exhaust, fmic , Greddy profec b boost conroller, etc. All the supporting mods to run the max boost on the turbo. I have had the turbo on the car for over 2 years now and it had boosted fine with no problems. Well the problem now is that I will not boost conisestenly more than the stock psi. If I turn on the boost controller and adjust it nothing happens most of the time. But then randomly some days the boost will go just as it was set on the controller, but it only lasts for a short period of time like maybe a half hour drive and then with no warning it will go back to stock psi. One time I happened to even be watching my boost gauge and I saw it go to the high boost setting 15psi and while I was a still accelerating it very quickly dropped down to the stock psi which is about 9 psi with my upgrades. I need some input on places to start looking. Please help.

P.S. Sorry for the long post.

[Sil80sushi]

just a guess not sure but vacum leak?

[IanS]

sounds like an issue with the boost controler, Im not to familiar with the profec B, maybe somone else can elaborate further.

[jaboc03]

I thought it might be a vac leak and I even found one in a spot where I had a t in the boost controller vac line where my vac gauge is hooked up, but I changed it out and the boost worked ok again for about a half an hour then all of a sudden it was back to stock.

[I ask good questions]

Like someone else said. Maybe the boost control solenoid has taken a vacation. It sais to place it in a cool dry place during install. Just a guess though.

[IanS]

Like someone else said. Maybe the boost control solenoid has taken a vacation. It sais to place it in a cool dry place during install. Just a guess though.

a vacation? unlikly, it problem went to the bathroom and then fell in, hehe.

[jaboc03]

That is kind of what I was leaning towards as being the problem. Is there anyway to test if the solenoid has gone bad? That way I can be be sure before I spend money on a new boost controller.

[CoupedUp]

You have injectors and some sort of fuel control right?

Have you tried just hooking the Wastegate up with no Boost Controller?

If it doesn't appear to be a huge leak. I dont know if a leak unless ungodly. Would cause this.

I would assume a bad Diaphragm or bad wastegate.

[jaboc03]

Yep. 550s, fpr, Apexi s-afc. I guess I should look into the wastegate a little more. The only thing is I thought if the wastegate was bad it would have trouble boosting in general? But I am so tired of this I got to check into every possible problem. If I can't figure it out this weekend I will probally drop the car off at my shop. I will keep you guys updated.

[jaboc03]

Well, it looks like my boost controller is the culprit. The wastegate and actuator are fine and no boost/vac leaks. I guess it is time for a new boost controller.