QuestionI have a 95 STS with 115,000 miles in mint condition. Every single thing works and every maintenence done at prescribed intervals (A,B,C & D). About 3 months ago I had to change the FPR due to hard starting and now about 2 months later it started to stall at idle and sometimes while driving. It will start right back up but then sputter and die maybe once or twice before it will run fine again for another 2 days. I then cleaned the throttle body plate and intake which was caked with black slimey residue and also de-carbonized the EGR valve & passages. I did an idle re-learn then drove it, it died at idle once again but now starts right back up and drives fine instantly. I have had Cadillac's my whole life and this STS is meticulously maintained. Electrical and Fuel delivery including the fuel pump all check out fine. The only codes I ever get is P095 Stall detected & I027 PRND321 switch failure. I am stumped, the only thing that sounds logical now is a Crank Position Sensor but I'm not getting any codes other than the ones I have mentioned. In addition, the idle is 600 rpm in drive & 775 rpm in park which seems low to me and it just sometimes feels like it wants to give up at idle. Please help me!!!
AnswerHi Adam, There doen't seem to be any magic answer for your problem but alot of checks that need to be done according to the book for code P095.
Where I would start is clear all the codes out and drive the car. If the P095 and the I027 come back after the engine stalls then I would do the checks for the I027.
There really isn't a spec that I can find for the idle speed however if the throttle position sensor reads 0volts + or - .5volts with the ISC motor retracted then the idle speed should be good. If not adjust the screw until it is. Then the ISC motor needs to be fully extended and there should be at least 10 degrees differance between the two readings. Idjust the ISC until it is. Then perform the relearn procedure.
Sometimes the ECM can have an internal problem with the board and vibrations can cause the engine to quit. Take the ECM down and with the engine running tap on the box with your knuckles on both sides and if it stumbles then replace it. Sometimes the negative battery cable where it attaches to the engine stud can work itself loose and that can cause all kinds of problems.
You already said that the fuel pressure appears ok. What I like to do is tape a pressure gauge to the windshield and see what the pressures are doing as I am driveing and when the engine acts up just to verify it is ok and not the problem. Also that the injectors don't leak down with the key off. Might even have a defective fuel pressure regulator. New ones can go bad.
Like you are thinking the crankshaft sensors could act up and cause the engine to quit. Around '00 Caddy had a problem with those sensors and replaced them both for that reason. Because your engine has alot of miles on it they could be starting to go bad. If you remove the electrical connector and see oil there or remove the sensor and where the magnet is on the end you see cracks then replace the sensors and the problem could be fixed.
Try those suggestions and see what happens. If you need diagrams the other Caddy expert can possably send you some depending on what you need. Let me know if you need anymore help. Bill
