Question about 1990 Saab 900 Hatchback
In short, it starts right up followed by a rough idle for 1-3 seconds before stalling out. Once it stalls, I can't get it start again for hours or until the next day and attempting to start it in between only causes a bad fuel smell. That problem was bad enough, but then things got really complicated...
The other day it started, idled noisily, but then kept running. The engine began to idle normally after about 20 seconds BUT the rpm's suddenly started climbing as if I was slowly pressing on the gas pedal then stopped around 3500 and stuck. The front of the engine started to smoke a little and smelled badly like burning ?oil or ?coolant... couldn't put my finger on it. I was in neutral with the parking brake on not pressing any of the pedals. Weird.
So I pressed the clutch in, put her in first. Once in gear I noticed that I could control the rpm's by playing with the clutch pedal (releasing while in gear lowered rpm's accordingly) BUT when I started to press on the gas, it acted like a choke and I almost stalled out again. I discovered that I could change gears and accelerrate completely by playing with the clutch pedal (since the rpm's would go back up as I depressed the cluch pedal or left it in neutral). WEIRDER. So my manual is almost an automatic now...??? Drove it up and down the street testing all the gears (all just by playing w/clutch - no gas pedal), parked again, shut her off... now it won't start again. Gas fumes after trying a couple times. Grrr. -_-
Checked the oil - bone dry and dirty, so I filled that hoping to stop the smoke and burning smell. Probably a leak there since it was full last week. Checked the battery, cleaned all the contacts, and charged it seperatedly just in case. Every Saab technician I've asked just shrugs like "i dunno, you're screwed". :(
Anyone here even heard of a problem like this?
The complete loss of oil suggests that you might have a piston problem!
First, check the compression on all cylinders; all values should be within a range of 10% from highest to lowest. Typical value about 140 psi.
One cause could be a blown piston or rings, allowing pressure into the crankcase, and blowing oil out of the filler pipe - very fine and barely visible, not spouting. You might feel the pressure pulses from the damaged or leaking cylinder.
If one cylinder has zero pressure, it's more than likely the cause of the problem. Do a wet compression test (pour a little oil into the cylinder immediately before connecting the compression tester - it usually seals any leaking rings for a little while) and if it holds pressure, that points to the rings; if no pressure again, that points to the piston.
Let us know the compression test results.
Posted on Jun 02, 2009
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Posted on Jan 02, 2017
Tips for a great answer:
This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve but always run a OBD2 fault code as well as the cleaning procedure. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control
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