Ok guys, got a good one for ya! I have been experiencing ongoing problems related with my car's performance (aren't we all) with boost control. My boost will spike consistently at around 15-17psi all day long but WILL NOT spool up to that psi until higher rpm's almost redline the majority of the time. I have been GIAC chipped and blowing the Forge splitter for about a year now and cannot spool that psi under load (mid throttle) most of the time. Now get this: About once every two weeks or so I will geta start-up that must reset something which makes my car perform the way it should. I get instant boost (15-17psi.) right away under load which is an unbelievable difference in my low-mid range pull; I can hear my turbo spool up and the blow-off which is much louder than it normally is. After about two start-ups it returns to normal, bogging down unless I really get on it. The difference in power is incredible so there is definitely something interferring electronically, I believe. Also note that when allis good, my cruise control actually works when the majority of the time it doesn't. I have made this relation with the performance and the cruise control which consistently coincide with each other every time I notice thechange.
I am constantly scanningfor codes and never have any appear during this interaction, NO DTC's. So farI have performed a *boost leak test = negative, *replaced N75 valve = negative, *double checked all turbo plumbing = good, *checked all fuses = negative, *replaced brake light switch (faulty brake light/ implausible signal dtc) thought it could be cruise control related = negative results, *replaced plugs = gapped correctly. I am out of ideas here andall I know is that I love my car when she's performing to her potential which hasn'tbeen too often.

*Also note that Ihave a split/ crackedcrankcase breather hose that is on back order from ECS Tuning that I don't think would have any influence on this problem...?? Any advice or information regarding this issue would be greatly appreciated, thanks again.

 

Auditech79 told me that a faulty brake light switch can cause all kinds of funky problems that you wouldn't expect (including engine issues) and since your cruise control seems to be tied in (can also be a symptom of a bad switch), maybe it's worth replacing, just in case...it's cheap, so it's worth a shot!

 

Thanks Sineo, your awesome in response to support within this forum; I have read so many of your inputs and have learned so much from you. Unfortunately I already replaced my brake light switch with a new one and STILL get that same DTC when scanning my autotrans...Faulty brake light switch - implausible signal. If I tap my brakes prior to scan I won't get that DTC.

 

Oh, wow, I guess I sort of petered out by the end of your post - I didn't read that you'd tried the brake light switch already. Well, it was kind of a long-shot anyway, so I guess it's an even longer one now, but it's very, very easy to ruin those switches during installation. Since you're still getting that DTC, I would think that that could be the case...but I guess I'd wait until the guys who know about turbos chime in before giving that a shot again.

 

No that's cool; considering I already installed a new one and I'm still receiving a DTC for that makes me wonder if IDID break it during installation. Although you mentioned it inanother post, that DTC is common and will always show up unless you tapyour brakes prior to vagscan.My brakelights and everything work fine but thereis also another brake light switch located directly below that one that has a vacuum line running into it that I still could not reasearch it's function on. I am now wondering if this is the faulty component causing all my problems, any ideas? I have posted before about my brake light switch in relation to my torque converter/ tranny issues I have been having as well. Why would this affect boost relatedproblems? Also, to my understanding my year doesn't support limp mode correct? Could I be going in and out of limp mode without throwing any dtc's? I don't get it, every time I scan my damn car it's clear, no codes present.

 

Bumped...