Date: 20 Sep 1998 02:17:43 GMT From: rubidiumnopsamdnet.att.netXX (Jim Collins) Subject: Re: Turbo Boost problems
In article <35FDA1C5.579nopsamnet>, jvanabranopsamnet says... > Paul Aspinall wrote: > > > > I have an 89 9000 Carlsson. I have had problems with Turbo boost for a few > > months now. The car seems to imtermittently reduce itself to basic boost for > > no reason (ie. the boost guage moves half-way into the yellow). > > Occassionally I do get full boost (all the way into the yellow), but it is > > quite rare. > > > > I have changed plugs, air filter, cleaned injectors, tried new boost > > solenoid - but no luck. > > > > Has anyone had this problem, or can anyone help??? > > > > Thanks > > > Did you try a new APC box? That would be the next place to > look. Either than or a vacuum leak. > > The APC box is the *sole* controller for boost. It interacts > directly with the APC solenoid, so if you're getting basic > boost, it's 'cause the APC box said so - given that the > solenoid itself is good. > > Now, things that will normally cause basic boost are a > failed apc box, a failed knock sensor (may give the > *illusion* of basic boost) or the cruise control system > being engaged or malfunctioning (check the pop-off valve > near, the clutch & brake pressure switches, and the > cruise control 'ecu' itself). > > My money is on a bad APC box, though. > > -Justin > I had this problem on my '87 900T and the fix was free....I don't know if your car is the same, but I'll tell my tale anyway. There is a vacuum sensor on the left front fender that has a vacuum hose going to the cruise control vacuum pump (located farther forward and lower in the same area. The purpose of this sensor is to limit boost to basic boost when the cruise control is engaged. If this is defective/misadjusted, it will keep you from getting full boost. There is a cap on top that allows access to an adjustment screw. Also, on my car, the APC box doesn't do a thing until you ask for more than basic boost (to prove it, try disconnecting the APC solenoid wiring). The basic boost is set with a mechanical waste-gate adjustment and is totally unaffected by any fancy electronics. Like I said, what I say here is true for an '87 900T. JC -- Jim Collins Issaquah, WA (206)295-6691 REMOVE XX from address to reply
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