Just this morning while driving into work, I had some running room at which I had to mash the pedal down. I noticed something different this time as I glanced over to the boost gauge.

Whats happening is, the boost gauge drops off a bit when I maintain steady acceleration. I just wanted to know what could be going on and why is it dropping off?

The pic below is the only pic of a boost gauge I could find on here since I didnt have a pic of mine (yes its a Canadian gauge, but I wouldnt know that until Bill pointed that out to me. Thanks Bill!!)

The red lines are what I get up to in boost and what it drops to. Anyone have this problem?

that happened to the 92 bonne ssei (siggy) but um i can remeber what the cause was :? sorry man

Convert to a Canadian boost gauge, it won't happen.



I'm not sure how mine acts. I don't stare at my gauge that much. But I'd check your vac lines anyway. If this is not what you normally observe then something could be wrong. Are you accelerating at WOT when it drops like that?

Not fully no. About 3/4 down just for a short run then I release the pedal. The weird part is the boost gauge is steady under regular driving but drops when I mash the pedal?

Ill have to get under the hood this weekend and just replace the vacuum lines so I know they are at least new.

Sounds like the BCS is dumping boost. Most likely for a reason. Can you scan? Changed anything recently?

My brother works for a GM dealer. I can have him scan it. What am I looking for?

No SES light, and as far as any changes, nothing has been done to the car since I bought it.

The kid before me I guess had a chip on it, air intake and smaller pulley, but was all stripped by the time I bought it.

Didn't you mention the kid before you got a code. Please post that link into this thread. It will probably help with the diagnosis.

Look for boost % or BCS duty cycle or something like that. That scan is going to have to be during driving. Try to replicate the boost issue. If it drops below 100%, the PCM is asking for boost dump.

Ahhh found the thread for you.

http://www.bonnevilleclub.com/forum/...ight=overboost

I'd like to say up front. I believe due to the thread that there was/may still be an issue BCS/BCA related to the code the previous owner had with "overboost". The club has learned a tremendous amount since this post and it will probably assist in looking at this issue as this is the SAME car.

Thanks for helping with the link Bill!! I'll have to talk to my brother and see when he can give me some shop time. I have no other issues when driving the car and everything seems to be normal. I just thought that the Boost should not be dropping when calling for it.

Im going to get under the hood this weekend and check/replace the vacuum lines and see if that helps. Also, can a visual inspection be done on the Boost Control Selenoid for damage? Where is it located?