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Yup, good memory! Its a '95 Aero with the TCS on/off switch. No traction control problems at all, and thankfully it has went into limp mode. It boosts up fine runs smoothly but its just rough at idle. With a cold engine it'll start up, get down to about 900 rpm and dip down to 600 and rev up..i'm sure its the classic vacuum leak with throttle compensation to keep the engine running. It wont sit at an idle. After it has run for a few minutes, the idle fluctuates between 1100 and ~700. Its a smooth fluctuation if there is such a thing, but every once in a while it'll dip down to 650ish rpm and have to pull itself up. Also the Check Engine Light is on, 6 flashes for oxygen sensor (which I replaced 2 weeks ago), and of course, the mileage has been in the teens. Symptoms have always been there since I purchased the car 2 years ago, and they are exaggerated in colder weather. It has gotten as bad as shutting off when I push in the clutch and put it in neutral. The thing that gets me is that the idle is rough even when the engine is warmed up.
I've unplugged every hose from the intake manifold and covered the nipple with a piece of rubber bike inner-tube. Doing this test, covering every nipple (not simultaneously) has the same result, which is the same or an even rougher idle. Ive checked hoses on the charcoal canister, every vacuum hose connection, checked intake manifold and throttle body bolts (they were all tight). I've measured the vacuum at 'idle' and it reads -16psi. If I hold my foot on the gas and keep the engine at 1500 rpm it reads -20psi and I know that is where it's supposed to be.
Some things to keep in mind for this specific vehicle: throttle body is TCS and electrically regulated, the car is OBD1 and thus has only one oxygen sensor, there is no idle air control valve or Air Mass Meter. Intake Air Temp sensor (on charge pipe) and Coolant Temp sensor (betw intake manifold runners #2-3) test fine. MAP sensor, Fuel Pressure Regulator, O2 sensor, TCS red/white check valve, Blow-off valve, hoses to the boost gauge are all fine. I've actually replaced most of these parts and have never noticed sudden changes in symptoms. Also, repeated cleanings of the throttle body have not helped the idle. All fuses in the fusebox on the passenger side have been tested/switched and they are all functional.
Today I purchased new crankcase ventilation parts just to eliminate these as potential problems. I noticed the hose was flimsy from being exposed to the heat. But after reading more Saabnet posts today, I decided I will change the PCV hose, check valve, PCV valve and bushing. I bought a new throttle body O-ring (mine was squished flat) and a new gas cap because mine was broken. So if the idle problems go away after I receive and install these parts, sorry for the premature post. The only other ideas I can think of are the the Crankshaft Position Sensor and the Throttle Body. My throttle body has been tinkered with, upon inspection I noticed somebody broke off a few screws and replaced them with gasket sealer! I looked over my receipts and I found that a Saab shop in Minnesota replaced the throttle body with a used one. I've read so many posts and have seriously tried to test everything that could relate to the idle issue. I'm stumped.
posted by 173.22.13...
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