Upon start up either hot or cold, my 93 SC-1 engine accelerates to 2500-3000 RPM and slowly decreases to about 1400-1500 RPM. The process takes about 30 seconds before the RPMs are low enough to shift the transmission into Drive. Gas mileage is down 30% and the engine accelerates back to 3000 RPM when shifted into Neutral or Park. Checked the OBDI and it only blinked out O2 sensor reading high. Any help or similar experiences from you guys/gals would be helpful. With gas prices heading towards $3/gal. I'd like to reclaim the 11-12 MPG I'm losing because of this engine problem.

 

L,


My 97 SL1 had bad connection to engine coolant sensor. Is thermistor that changes electrical resistance with coolant temperature. Thermistor itself was ok. Connections on end had gotten wet and made poor connection.


When thermistor is cold...device resistance is high around 4-5K ohms...As engine coolant warms...resistance should reduce to 200 to 300 ohms. If you have VOM you can check this and also voltage on end of wire going to thermistor...Key on...engine NOT running.


This is one place to try.


Good luck L,


gpers

 

o2 senser maybe....check your intake hose for cracks, holes, ect..check your gap on the spark plugs...

 

Replace Engine Coolant Temp Sensor and connector-- especially if it has never been replaced --



$20 and 20 min (get brass-tipped replacement from Saturn Parts dept).



Also, clean throttle body.



If problem persists, may be Throttle Position Sensor or Idle Air Control Sensor.

 

I would check the pcv hose for a split for sure.Good call heatherpoo.Start the engine and spray some short bursts of brake clean around the intake manifold gasket area and the pcv hose area. If there is a leakthebrake clean will cause the engine to idle down for a few second when you are hitting the right spot.

 

I had that problem on a 93 SL. I changed my PVC and my fuel filter. Idles fine now.