Gigs throttle body install, troubleshooting reduced boost pressure

[jfk33]

Hi all,

I just installed the Gigs TB on my 4v BW. As always, the hardest parts were getting plastic pieces to cooperate -- I thought bolts and that sort of stuff were easy to access in the engine bay. Pleasantly surprised!

I read through DesertRJ's thread on his installation experience, and am having the same issue with a CEL and reduced boost pressure (currently limited to 6lbs). I checked all the vacuum lines and connections suggested in that thread and so far, I've only been able to get rid of the "Reduced Acceleration Drive Carefully" message on startup. The CEL is still on and boost is still limited.

I don't have a scanner I can clear the CEL with at the moment, but my question is if things are OK (it's been driving just fine), will the CEL eventually clear after a few drive cycles? If I disconnect the neg terminal of the battery and leave it for a few hours will it clear?

And if it clears, will the ECU give me my boost back???

Thanks all for any ideas/comments/observations/buffoonery you offer!

***Important Edit***: as you'll see below, this is relevant. The first time I started my car (after following the instructions to turn on but not start the engine and slowly depress/release the accelerator x3), I had forgotten to plug in the Q40B Turbocharger Bypass Valve Solenoid - Bank 2.

 

[Eberk]

You can go to autozone or similar place and have them clear it for you. Not sure if it will clear by itself. May want to try and few ignition cycles maybe.

 

[Eberk]

Have also heard removing negative battery cable for like 5-10mins maybe

 

[jfk33]

Update:

I went to NAPA and borrowed a scanner (probs right as Eberk was replying). The code is P00C0 "turbocharger bypass valve B controller circuit".

According to the GM service manual for the Ct4 (I paid for the 3 day subscription at ACDelco) the code gets thrown when "Control — Q40B Turbocharger Bypass Valve Solenoid - Bank 2" is in the state of "Open/High Resistance" or "Signal Performance".

All that only sort of means something to me. Either way, I cleared the CEL but I'm still in low-boost mode.

I'll be over here Googling, but if anyone is still out there and can help, I'd appreciate it. Thanks!

 

[Eberk]

Did you check the electrical connections as well. I left the one on drivers side off twice actually lol.

 

[jfk33]

Another update:

I tracked down the part "Q40B Turbocharger Bypass Valve Solenoid - Bank 2" in the GM service manual and it is in fact the electrical connection I forgot to hook up on first start up after installing the TB. I figured this out after the first drive around the block so since then it's been connected.

I'm guessing this is why the code got thrown and I'm in limp mode now. I just went back out to the garage and disconnected the bypass valve solenoid and reconnected it, making sure it was tight. I've disconnected the car battery and am going to let it sit for a while and see what happens on startup.

Wish me luck, and please keep firing away with any suggestions you think might help!

 

[jfk33]

Did you check the electrical connections as well. I left the one on drivers side off twice actually lol.

I was literally typing my most recent reply about forgetting the driver's side solenoid when you sent this! lol

 

[Eberk]

I was literally typing my most recent reply about forgetting the driver's side solenoid when you sent this! lol

lol I actually forgot that damn thing twice. I had trouble getting it to clear with hp tuners and think it finally cleared on its own. Hopefully the battery will do the trick.

 

[jfk33]

Another update:

So 3 days on and the CEL hasn't thrown again and I'm not getting the "reduced acceleration use caution" msg on the dash at startup. Things feel right, but my boost gauge indicates I'm a VAST majority of the time only hitting 5-6psi of boost, even after 5-10min of driving to allow oil temps to come up. Today on the freeway I did WOT pull and hit 9psi, but a lot of the time, even with WOT pulls I'm hitting a steady state of 5 or 6psi.

Am I still in a limited boost state? If it peaked at 9 on the freeway should that tell me everything is all good and I just haven't needed more than 6lbs if boost? I've searched around and most people hit 11-12lbs normally. For what it's worth I'm in Maine and it's 45-55f out, so maybe I don't need that much boost to hit target torque? My understanding is that's how our ecu does out boost pressure -- it's targeting engine torque.

I sent essentially the same answer to @WONT TAP on their website, so if I get an answer there I'll post it here!

 

[WONT TAP]

There are two vacuum lines that commonly get missed when people replace their throttle body and/or spark plugs. We have pictures of both at the bottom of the spark plugs page of our website. The one that's toughest to see is the one most people miss.

Brisk Silver Racing Spark Plugs (6 pack) - Tapout Tuning

Note: Did you recently replace your spark plugs and now only have 7 to 12 psi of boost? Every day we hear from people who change their spark plugs and then only have 7 to 12 psi of boost. Most of the time there’s a simple solution to this problem. Pop the hood, let the […]

www.tapouttuning.com

 

[jfk33]

Final update:

Scott from @WONT TAP was spot on! The vacuum line I missed was the one hidden by the black plastic piece the wastegate solenoids are mounted on -- once you put the vacuum assembly back in place that vacuum line is super hidden and I'm not surprised they have a special section in their spark plug article JUST about those two lines.

That said, @WONT TAP was incredibly fast in responding to my emails and were right on about the problem. Props to them as a company and Scott as the owner replying directly to customers. Awesome all around!

 

[WONT TAP]

Nice work finding the problem John!