1994-2002 [Subscribe to Daily Digest] |
 | [Main NG900 & OG93 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
There is lots posted on this BB about engine idle... Posted by REM in Seattle [Email]  (#4)  [Profile/Gallery]
(more from REM in Seattle) on Sun, 18 Sep 2005 09:41:52
In Reply to: High Idle-Intermittent, Spencer, Sat, 17 Sep 2005 17:51:36 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Search on "engine idle" to find previous postings.
Generally, there are two modes of engine idle problems; engine idle too low and engine idle too fast. The ECU (engine control unit) computer is responsible for maintaining the engine idle. At idle the throttle body butterfly valve is closed, and the ECU controls idle speed by opening and closing the IAC (idle air control) valve to allow more or less air to bypass the butterfly valve and into the engine.
Low idle usually means excess air getting into the engine. Engine idle too high means too much fuel being delivered to the engine.
Check all vacuum lines and components for leaks, split hoses, bad connections, etc. There are vacuum lines to the fuel pressure regulator; the boost by-pass valve; the MAP (manifold absolute pressure) sensor; the PCV (positive crankcase ventilation); the IAC; and the charcoal canister purge valve. A visual look at the hoses, etc. may find most problems, however a device like a my-ty-vac is handy to be able to pull a vacuum on each line and verify there are no leaks.
Clean the throttle body exterior, making sure the throttle linkage and the cable are lubricated and operate freely.
Clean the throttle body interior making sure that the butterfly valve operates smoothly and easily.
Clean and lightly lubricate the IAC valve.
On 1999 Viggen and 2000-2002 9-3 there is a MAF (mass air fuel) sensor that directly senses the amount of air coming from the intake system. A faulty MAF sensor, or leaks in the intake plumbing, can cause the ECU to be mis-lead about the amount of air entering the engine.
The throttle position sensor may be faulty. The throttle position sensor tells the ECU the position of the butterfly valve and therefore the amount of air entering the engine. This is used to calculate the amount of fuel that should be delivered.
Make sure that ground wire connectors to the engine and chassis are tight. A bad ground can confuse the ECU.
There are signals from the air conditioner and the automatic transmission that are also processed by the ECU and used to make adjustments to the idle speed.
REM in Seattle
2005 Saab 9-3 Aero Convertible; 5-speed; 6000 miles
1998 Saab 900SET; 5-door; Automatic; 79,000 miles
1984 Saab 900T; 3-door; 5-speed; 242,000 miles (RIP)
_______________________________________ REM in Seattle Current: 2013 Volvo XC60 R-Design, Rebel Blue, 3.0L 6-cyl turbo, Automatic 2024 MINI Cooper S Convertible, 2.0L 4-cyl turbo, 6-speed manual Former: 2005 Saab 9-3 Aero Convertible, Steel Gray metallic, 2.0L 4-cyl turbo, 5-speed 1998 Saab 900SET 5-door, Silver, 2.0L 4-cyl turbo, Automatic 1991 Alfa Romeo Spider convertible, Alfa Red, 2.0L 4-cyl, 5-speed 1984 Saab 900T 3-door, Red, 2.0L 4-cyl turbo, 5-speed
, Sun, 18 Sep 2005 09:41:52 <-- Viewing This Message
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
