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Date: Mon, 16 Apr 2001 14:10:16 +0100
From: Paul Halliday <>
Subject: APC Solenoid Valve Problem?

I have had a recent(ish) problem with by 1988 900T (150K miles) which manifests itself as poor performance and low boost pressures. The APC gauge only reaches about half way up the yellow part of the gauge, but the RPMs do reach about 4000, and there is no noticable "boost". I have read up on this and followed conventional advice from a number of articles that I have read. I have disconnected all the hoses to the solenoid valve (R, C & W): * With the key off and the power to the solenoid disconnected, when I blow through C, the air comes through W with none through R. This is the normal state of affairs, so I am led to understand. * With the key on and power connected to the solenoid valve, air blown through C continues to come out through W with nothing through R. This is wrong? Is the solenoid valve at fault because of this diagnosis? I took the car onto a straight flat road and disconnected the hose from C at the throttle housing. The performance was generally weaker (obviously because of the atmospheric hole in the system), slowly building the car up to about 30 MPH and to third gear I gave it a little more gas and off it went. The turbo gauge charged straight up to the maximum (way past the end of the red zone), the car "boosted" noticably and nearly stalled - fuel cut out?. At this point I immediately stopped and reconnected the hose to the throttle housing ... back to how it was. 1. Should I have removed the C hose at the solenoid and blocked up the end of the hose connected to the throttle housing to perform this test correctly? Is this "safe"? 2. Since there _appears_ to be a fault with the solenoid valve itself, could this be electrical rather than the valve at fault? The solenoid valve makes 3-4 loud clicks in very rapid succession when the ignition key is turned to the start up position. I presume therefore that the 12V supply is getting to the valve. Is grounding an issue here? I am taking the car into a Saab specialist garage next week to have an oil leak looked at, which is "no problem" according to the mechanic and the reason for the chattering in the rocker box. I am *very* short of ready cash at the moment and I would like to have the performance addressed at the same time as this urgent oil leak. I would be a lot happier if I could point him to a specific problem (from other Saab drivers' experience) then and there, rather than return the car later when I have more surplus cash to throw at labour costs and numerous tests. It is possible that the oil leak is contributing to the poor turbo performance and the solenoid may well work fine once this is remedied, or can the solenoid be condemned now? Onto the oil leak. The car came with no history, so I have no idea what was used before. I did an oil change to replace the oil filter and the oil itself, filling up with fully synthetic 10W40 Castrol GTX. The leak appeared to start after this, but it could be coincidence. It is not falling out of the sump nut - I did put this back on correctly and the oil filter is not leaking. I have read of similar things happening when moving from mineral to synthetic oils, when mineral deposit clogging up small holes and leaks are removed. What is the current thinking regarding oil? Is Castrol GTX a good one? My previous car (Fiat Punto GT ... yum!) *loved* Mobil 1 0W40 - is this a safe oil to use with a 13 year old Saab Turbo? Many thanks in anticipation. Paul

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