I'm a new member. I've got a 97 bonny SSEi with almost 200,000 miles (308k) on her and now have my first real problem with it. It is not producing full boost under WOT, it only gets to about 30-40kpa (about half way on the + side), once in a while it will make its way up to max boost but rarely does it. I have had the boost control solenoid changed and it has helped a bit, now I get boost, before I would get some boost only once in a while. Would a bad O2 sensor contribute to the problem? I have changed the front O2 sensor and will be changing the rear this week. The vacuum actuator seems to be working fine, I cleaned it up and sprayed some wd40 on it to make sure it doesn't stick. What else can I look at?? Thanks in advance and by the way, fantastic site. I've learned a lot so far.

The O2 sensors will have nothing to do with this problem. The MAP sensor can, though. If you're actually getting full boost, but indicating less, it'* likely the MAP. I've never seen a bad gauge yet (that'* good news for you).

EDIT: I'd really like to see you hook up with someone that has an autotap or OBD2 scantool that can read actual boost, not just the Duty Cycle of the BCS. This would tell you what the MAP is seeing. You might want to do a comparison with the other 96-03 SSEi'* here and see what average boost they're achieving. The Series 2 produces less indicated boost on the gauge than the 92-95 Series 1, but the actual flow is higher.

The first things I'd check though, are ALL the vacuum fittings on the engine, particularly the fittings on the vacuum accumulator. This is the little black box mounted to the firewall next to the windshield wiper motor/gearbox assembly. A vacuum leak can make the boost bypass act up and not full actuate. Assuming all your vacuum lines are good, and no leaks are found, I'd suggest the MAP sensor since you've already done the BCS.

Don't change the rear O2 sensor. It does nothing for performance, and is only a 'final check' for emissions, to determine whether the Catalytic Converter is doing it'* job. Replace it only if it dies completely, and you can't stand the SES light.

Some good points from Willwren above to check. When is the last time you replaced the Supercharger belt?

Cheers,

I put a fresh belt on from Gates. I looked up on the hood and lo and behold, there is some rubber residue up there. The belt could be slipping. It could be from the old belt that was on that fell apart when the tensioner pulley wore out and was letting the belt slide off it and all over the supercharger pulley chewing it up completely.
I'm going to clean it up tonight and see what happens. I am getting the car scanned tomorrow and the rear O2 sensor replaced, (I have the new part). There aren't any vacuum leaks ( I had one last week in the control box for the a/c and had it fixed along with the bcs).
Lets see what happens with the belt, do you think it could cause intermittent problems??
I found with the vacuum actuator that it sticks a bit when you pull it all the way down, could this be the problem?? Is there a way to clean it up and lube it properly??
Thanks for the speedy replies guys.

After cleaning up everything, lubing up a couple of pieces here and there, the blower is working fine now. I guess a vacuum leak can cause havoc with the blower since it is both vacuum and computer controlled. Once in a while, my a/c gets stuck in full cold and des not mix in any heated air for the climate control. The vacuum actuators in the control box are either sticking or are shot. This causes a vacuum leak that messes up my boost once in a while. When it works fine, I get full boost, when it is not working right, I don't get full boost.
Thanks for the replies guys.

ur quietly welcome and u might want to get that vacuum actuator fixed

Kenn, he already did. That was the cleaning and lubing part.