Hello everyone...this is my first post to the forum. My 2003 SSEi has a low boost problem. I get full supercharger boost when it'* cold..first started. When it gets to operating temp only get 1-3 lbs of boost. Have replaced all vacuum hoses, checked regulater, and various connectors. No luck. I have read that the PCM lowers boost for various reasons...high engine temp, if it senses abuse of the vehicle, tranny in reverse. None of these reasons seem to fit. Any ideas from anyone. Thanks in advance....

With the engine not running, observe the position of the arm on the boost control actuator. Move it by hand to get an idea of the range of motion. Start the car, and observe the position of the arm at idle ... it should be opposite from where it was when the engine was off. Now move the throttle by hand while observing the BCA. As the RPM'* climb it should move all the way to the position you observed with the engine off.


Now, remove and plug the vacuum hose going to the boost control solenoid and take the car for a spin. You should have full boost at all RPM'* (high vacuum = low boost, low/no vacuum = high boost). Don't do this for more than a short ride or you will damage the engine. Just do it long enough to observe the boost gage. Couple of WOT'*.


To my knowledge the PCM does not lower boost for various issues. Low boost generally means the BCS or BCA need to be replaced. The observations above will tell you which is the problem.


If the BCA arm does not move through the full range of motion, remove the arm from the butterfly valve in the intake, and see if the butterfly valve moves freely. If not, clean and lubricate it until it does.


If you get full boost when you remove the vacuum hose from the BCS, replace the BCS. If the BCS is operating properly, the butterfly valve moves freely and the BCA arm does not move through its entire range of motion, replace the BCA.


Confused? Ask questions.

Thanks for the info. I have checked the BCA already...will check the solenoid next. Don't understand why it only acts up after the car has been running for 10 minutes or so. I get 7-9 lbs boost when its first started...

Try a couple WOT'* with the BCS vacuum hose disconnected and plugged after the car has been running for 10 minutes or so. If you run the car for 10 minutes or so (until your boost drops), what happens if you turn the engine off and immediately re-start? Do you still have low boost, or does it have to run another 10 minutes until that happens? In other words, is the loss of boost related to running for 10 minutes, or to the engine being warmed up?

PCM can and does pull boost using the solenoid. If it starts to see too much KR or misfires, it will open up the bypass. Newer models that have Traction control etc will use that also.

Once it is warmed up it runs the same. Max boost is about 3 lbs. Turning the key off doesn't change anything...

Try a couple WOT'* with the BCS vacuum hose disconnected and plugged after the car has been running for 10 minutes or so. If you run the car for 10 minutes or so (until your boost drops), what happens if you turn the engine off and immediately re-start? Do you still have low boost, or does it have to run another 10 minutes until that happens? In other words, is the loss of boost related to running for 10 minutes, or to the engine being warmed up?[/QUOTE]

Once the OP confirms the BCS and BCA are functioning properly, the next step is to scan for knock retard.

Don't call me a retard.

Thanks everyone...the BCS was bad. Everything is great now! The SSEi is back

Glad you figured it out. There are other factors that affect boost, but in my experience, when boost drops off 90% of the time it is the BCA or the BCS. By the way, there may be a mod you can do that might get you a little more boost. Loosen the screws on the BCA, move it to the left as far as it will go, and re-tighten the screws.


Thanks for reporting back.