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Intermittent base boost and oil out of dipstick SOLVED!! (long)  3 Saabers Like This Post!
Posted by coepercussion [Email]  (#2117) [Profile/Gallery]
(more from coepercussion) on Mon, 21 May 2018 11:57:14
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I posted recently about the problem of oil coming out the dipstick tube under hard boost (that is, when my car would boost properly) on my 85 SPG. I checked all of the common things to check, PCV system, the timing, did a compression check to see if the head gasket may be bad, and all of these were fine. I decided to check my O2 sensor readings and discovered I did not have 12V at the pre-heater socket to the O2 sensor. I pulled back the shrink wrap on the main wire harness where the ground and power wires run for the pre-heater and discovered that someone had cut both the ground for the pre-heater and the ground for the surge suppression diode for the AC clutch and just taped the cut wires into the harness under the shrink wrap. I re-connected those, and replaced the missing parts the ground wires that terminate on the grounding point on the alternator and got battery voltage on the pre-heater for the O2 sensor, and also the correct voltage swing on the O2 sensor signal wire.
At this same time while trying to diagnose my intermittent base boost I removed my knock sensor and went for a drive with it wrapped in a towel...still no change, it was stuck in base boost. (meanwhile over the last 2 years I've checked ever component of the APC--the solenoid, the pressure transducer under the dash, replaced the knock sensor itself, checked all connections and grounds, and even swapped the APC box with a known good one, and made sure my ignition components were all new--plugs, bougicord wires, new cap and rotor...still only had intermittent full boost)
So, I removed the knock sensor connector and bridged the two connections at the connector on the knock wire and checked for continuity at the wires going into the APC box....got none! Traced the knock sensor wire back to the firewall to find it had been spliced at some point and the connection at the splice was bad. Removed the crappy connectors someone had used and soldered the two wires and the shield wire and shrink wrapped everything. Checked for continuity again at the APC box and it was good! I reinstalled the knock sensor and did a quick 'hit with my socket extension' test and got good clicking from the APC solenoid. I then went for a drive and had FULL boost! Better boost than this car has ever gotten...close to the 11 psi level and slightly into the red on the stock gauge, which is right were it should be. It was a 'get out of jail' feeling, finally having solved it. AND the icing on the cake of everything is there is no more oil coming out of the dipstick either. I can only guess that the O2 sensor issues caused the wrong fuel-air mixture (probably running lean) and this must have caused higher than normal exhaust temps causing valve issues and allowing the crankcase to pressurize. Is that possible? I'm not asking any questions I'm just glad the issue has been solved. Been driving it for over a week with no issues and idling and running better than it ever has! Finally solving base boost has got to be one of the best feelings a C900 owner can get.
, Mon, 21 May 2018 11:57:14 <-- Viewing This Message
3, Mon, 21 May 2018 17:07:02
, Mon, 21 May 2018 18:45:32
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