Aroooo

hey guys. long post but here goes need help 08 ss tc. car had k&n intake, zzp fmic, 4.05 swap, 23psi trifecta and always ran great. lost engine, replaced with 2010 lnf, new zzp catless downpipe and new eBay exhaust. since car has been back together it ran poorly at first, little to no boost. ended up bypassing the vac tank and boost control solenoid and instantly started making 23 psi. car runs great in both stock and trifecta for about 20 minutes. after 20-30 minutes it will only make abound 16 psi, sometimes spike to 20. stock tune makes 10 and less. both tunes feel a lot slower especially stock. car will act the same way the next day If I leave it overnight. but if I take the lug off the battery for 15 minutes, everything goes back to normal for probably 20-30 minutes.. is this a tune issue? because I bypassed the boost control solenoid, and added a 3" catless downpipe? the ecu seems like it learns itself and keeps my boost down. no codes.. need serious help

ECaulk

iTrader: (6)

Well to find out if there is a code stop reseting the ecu. Some codes require multiple key cycles before they're set.

I'd guess it's because your bypassing the boost control solenoid, the ecu is going into protect things mode. If you're tuned for a boost control solenoid replace it if it's actually bad.

Aroooo

thanks! seems to be bad as I couldn't make any boost until I bypassed it. @no_ss and a few others said it was fine to run without. and tbh it's been doing this for weeks but I've only figured out yesterday that resetting ecu would let me hit full boost again. I just took off my evap purge solenoid, I could blow air through it with ease. would this do it after pressure building up over a period of 20 minutes or so??

Slowbalt2000

iTrader: (1)

if you could blow through the purge solenoid, its bad. Major boost leak

ECaulk

iTrader: (6)

Yup.

As far as running without a bypass solenoid, you can do that to diagnose the issue. Then you need to get a replacement.

Aroooo

from what I understood I could run without it. heard they're expensive and I could run without it. could I go aftermarket like grimmspeed manual or electronic boost control solenoid?? I just bought this car as a cheap find. I put a new front end, brakes all around minus two front calipers, shifter cables, engine, oem clutch, zzp downpipe, eBay exhaust, rear sway bar bushings and end links, 225 40 18 tires brand new I put on yesterday with the brakes and front end and bushings and a battery... car also had a zzp fmic and k&n intake but that isn't new. was really hoping to not throw money randomly at this car in hopes of it solving problems but I believe I need the evap sensor and bypass solenoid.. and is there a vent in the gas tank that maybe collapses or solenoid messes up? I used to have trouble starting after fueling up.

ECaulk

iTrader: (6)

It's US$46, I know exchange rate and taxes kill you Canadians, but even at $100 it's not that bad.

Here's a link Ecotec LNF Bypass Valve Solenoid 12633411

And here is the part # if you have a dealer nearby 12633411

But I'd fix the evap first then move to the control solenoid.

Aroooo

exchange rate plus duties which sucks. but at just over 110/120 bucks thats not bad. closest dealer is an hour away. I'll be ordering that evap solenoid right now. after that's done I'll do the bpv solenoid. thank a bunch. will bump the thread and update when I have things updated!! thanks bud

Aroooo

ok so I got my evap solenoid for 31 dollars (step father owns car quest here). haven't driven it much but the car seemed to reach and hold its boost much better. except for first Gear.. can only get 80kpa at the highest peak. second gear 160kpa.. only place to get the bpv solenoid is the dealer and it's 113 dollars. I'll be ordering that Monday

ECaulk

iTrader: (6)

Is that on the trifecta tune? Did you build a boost leak tester?

no_ss

iTrader: (2)

I run my car daily without BPV solenoid and it runs perfectly fine. Boost control is not through BPV.

Aroooo

it's in either tune. in first Gear I might hit 40 kpa or 80kpa. about 11psi max but it's usually around 7. I borrowed a buddies boost leak tester and found no leaks.
how's boost control done? tune? my car worked extremely well until I lost the engine. I replaced it and now I am limited in boost in first Gear.