Turbo GS300 problems: Experts check in!

[savanna13]

First off: 1G GS300 Aristo GTE/Auto with single 70 trim T4 and Tial 38 (10LB spring, Greddy Profec B to hold boost at 14 LBS), running stock 440's and an SAFC with a full 3 inch exhuast.

One day 2 weeks ago, I was driving my car to work and it started hesitating and acting strange, idling erratically and dragging no/light boost part throttle shifts out for wayyyyyyyy longer than normal. I immediately pulled the plugs to find that they were covered in oil, which was not much of a surprise because of my leaking valve cover gasket. I changed the valve cover gasket, the plugs, and did a compression test (180 across the board). After I broke all of the coilpack connectors and had to order new ones from Toyota, I plugged everything back in and took it for a spin, only to find immediate gayness.

Like I said, it idles like it only has 5 cylinders or a nasty cam, but only sometimes.... when the vacuum drops from 20+ lbs at 650RPM idle to about 12-15 lbs. It also causes my Air/Fuel ratio to go nuts... crazy lean or rich, depending on what seems to be its mood. OK, so it has a vacuum leak, right? The only leak I could find was my intake manifold gasket (using starter fluid while letting the car idle to listen for surge). There is just one hangup: Ever since it started doing this, my car will not hold boost below 14lbs, even with my boost controller turned off (running off of the 10LB spring alone). It will blow to 18-25 LBS IMMEDIATELY, provided the car is anywhere above 3k RPM. WTF?! Could an intake manifold gasket leak cause extreme boost spike?

HELP ME!

I plan on replacing the gasket and upgrading the injectors to Supra 550's (with twin DSM resistor boxes) when I pull the manifold.

Can anyone confirm or relate to this? Thanks in advance!

[Z U L8R]

check your waste gate, i'm assuming you have a dump tube, take off your dump tube and with a flat head try moving the valve open and see if it slides up and down smoothly. also check the vacuum hoses that run to the waste gate & profec, check the vacuum hose that runs to the profec control head also. it'd be best to tap into a vacuum bung on the plenum, open the throttle body and pump smoke in it with a smoke machine. we have one at our shop.....check the hoses i mentioned and post what you see. good luck =]

[savanna13]

I will check these items. Thanks!

Anyone else?

[Elbow]

I dont know, but omg I wish I had a turbo GS300.

[2turbo4u]

Ask the question on CL in the SC sections. Maybe call Mike @Mainstream and talk to Turbo Dave he might be able to help you out. GS3 ftw!

[2turbo4u]

Did you car come from the south, mines came from Philly and it had to be retuned once I got it down here brcauseof the atmosphere difference. It was hesitating badly.

[savanna13]

No, mine was built here.

[Z U L8R]

what's new with the car? what did you find?

[GGPIS3]

it does sound like a wastegate issue... can't be a bov problem if you're creating too much boost. i would also consider the coilpacks as an issue, but i dont see how that would affect boost levels.. only a consideration for the eratic behavior of the motor... but that would also only be under load, not at idle.

maybe its 2 problems... not just one. either way.. good luck and let us know if you figure it out.

[savanna13]

Nothing yet. The car has been parked and I'll be replacing the injectors/IM gasket on Tuesday night.

I'll keep you guys posted. Thanks again for all the suggestions.