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Sounds like your wastegate controller is tired and needs to be reset. Get your hands on a calibrated boost gauge and tap it into a tee on a vacuum line with a section of hose to reach into the car so you can read the boost when driving. Unplug the solenoid and read base boost under full load in 3rd gear. Should be 5.0-6.0 psi, and i'll bet you're only at 3.5 psi. Every one that I have checked with your symptoms was around 3 psi. Shorten the wastegate controlling rod to set at proper level. BTW it's a good idea to loosen up the wastegate rod when the car is cold so you don't burn yourself when adjusting once the car is warmed up. When you have plugged the solenoid back in, you should now get full boost up to the red border with stock APC settings.
Since you do did not mention either off-boost or on-boost knock with 87 octane gas, I also suspect that your timing might be closer to 14BTDC(or less) rather than the 16BTDC spec. Check it out. If the timing is set right, you should be experiencing off-boost knock under load at low RPM's while using 87 octane gas(the knock sensor only cuts boost through the APC and does not retard spark of-boost). I would always run premium gas(92-93 octane) and for less knock sensor boost cut, you can run 94 octane, if available, or throw in a bottle of octane boost. I have tried octane booster and find that I can run all the way to the end of red without knock, but do not use it much anymore. It leaves a brown deposit on the plugs and may not be great for the catalytic converter(rumor??) and it gets expensive at $5 per tank!!
When you tweak the APC potentiometers, you will notice a sharp boost drop when the knock sensor kicks in. To avoid this and still maintain higher than spec boost, you can try 2 things without resorting to MSD or a SPG9 distributor advance/retard unit. First try setting your timing back to about 14BTDC, which should reduce the tendency to knock under full boost without sacrificing too much off-boost performance. If you are not satisfied with the off-boost performance and still get knock under boost, then you can try bending back the small round retard stop on the distributor vacuum advance/retard unit slightly. This will give you more retard under boost and permit you to set your basic distributor advance back to 16BTDC or even up to 20 BTDC depending on how much you bend the retard limit stop. This stop is very sensitive and you should not have to bend it more than a mm to achieve the desired effect. Somewhere on this or the performance board there are specs relating retard to "stop distance bent" and basic timing settings. But you can do it by trial and error.
posted by 216.75....
, Sun, 2 Dec 2001 17:29:29
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