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Anyone know all of the possible causes of base boost?

753 views 7 replies 4 participants last post by  YoungSaaber 
#1 ·
Hi all-been eliminating the different causes as to why I'm stuck in base boost, and wondered if anyone can add to this list of possible causes. Here's what I've checked/know:

APC-assured from a very reliable source that it was 100% good in his car 4 days before I tried it, so this seems UNLIKELY to be the cause, but possible.

Wastegate rod popped off-checked, it's fine

Brake light bulb failure/dodgy connection-checked, all light up when braking, and no warnings on display. Without a display warning is it possible something could be wrong?

Cruise control-a possibility. Mine has never worked on the car, and apparently cruise issues can cause the car to go into base boost, but what do you do if it does? How do I disconnect the cruise/fix this? Will I need to trace the fault in my cruise and fix that and then risk that not even being the cause? Because I don't want to mess around sorting it if that's not the fault, I never used it on my old one anyway.

What else? Currently I'm assuming the wastegate is ok, the brake lights are fine and the APC is ok. So it's possible it's the cruise, but I'm sure there are other things that can cause it. I know there are Saab master technicians etc on here who must have a complete list of all the things that will set the ECU off.
 
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#2 ·
when this list gets completed, it should be stickied... going through the same thing, but my cruise works great, just replaced DI and new plugs, new(used) APC, wastegate rod - if it is disconnected, wont you get the same boost even with the W hose disconnected? - brake lights - just replaced all the bulbs because of one going out, then a few days, another, and then another, till i got tired of replacing them one at a time and did them all at the same time...
AFAIK, a failing DI cassette will also throw you into base boost, as will bad plugs, for not getting the proper reading from the resistors in the plugs... other things to check would be all vacuum hoses for leaks, and anywhere the boost travels, such as to the intercooler, the plastic caps on the intercooler crack sometimes, allowing air to escape, dropping you down to base boost or lower, and it may fluctuate as well, could be confused with boost creep..
HTH
 
#5 ·
When I first purchased my 9000 the wastegate rod was off, and it wasn't til I fitted a boost gauge that I found this out (LPT Model originally). I bet that's why I got a good deal on it!

Have you checked the lines? Make sure the APC controller is hooked up correctly, in the LPT cars there is a tube connecting the wastegate to the output and relies on the internal mechanisms to hold the 5psi. You say that you recently fitted the APC, it's possible your lines are flopped and you've basically done this to your car with the APC module instead of having it fitted properly.

Try disconnecting the W hose, your car should boost til fuel cut, but carefully test drive it, as there is no control once you temporarily disable the APC system and let it run wild. That will rule out any turbo specific issues.
 
#6 ·
Hi Shinobidice, thanks for the reply. I'm pretty sure I connected the APC fine, and the hoses look and feel ok, but I guess it's POSSIBLE. I've also checked the wastegate rod, which is definitely attached fine (I can't wiggle it at all), and I tried removing the wastegate hose and driving it a couple of weeks ago and was making 1.5 BAR (car is stage 3), so there's no mechanical issue STOPPING me getting the sort of boost I should be. I'm just a bit stumped and don't WANT to go to a garage, but I think I've looked at everything I can think of.
 
#8 ·
Well, no basically. Today me and a mate finished installing an HKS EVC 6, and while I haven't had much chance to play with it basically I'm boosting to 1.3-1.4BAR easily, just need to fully finish sorting the settings and a little vacuum problem I noticed the other day.

I know it wasn't anything mechanical, so I'm pretty sure it was cruise control, but a) I don't like it anyway and b) for the money it could cost me to fix it, for something that only MIGHT work, I decided it wasn't worth it. I like the EVC anyway-allows me to control my boost up/down/have different presets for if the parents ever get behind the wheel...
 
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