Mechanics

UNDER\OVER FUELING?

1999 Saturn SC2 • 4 cylinder FWD Manual • 210,000 miles

Got a 1999 Saturn SC2, just changed Clutch kit, I think I''ve got some sensors crosswired because it idles normal (no hesitation) but driving it acts like it's only getting about 10 to 15 mpg?
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Mstanphill
January 3, 2011.




So it ran alright before the clutch job?Most of the sensor's on that engine you cannot plug the wrong connector into the wrong sensor. Especailly the sensor's you would have had to unplug to replace the clutch. Do you have any code's?


Saturntech9
Jan 3, 2011.
Unsure on codes just noticed check engine light burnt out and was thinking no codes were being set. When I put the engine/trans. Assembly back in the fuel sensor, CPS, and one other sensor had lost the labels I put on them. The two manuals I have on this car, niether one gives a diagram of the PCM or engine compartment, nor any good pictures of these sensors to tell if I have them hooked back in right.


Tiny
Mstanphill
Jan 3, 2011.
Well the sensor that goes to the coolant temp sensor that is screwed in the head below where the upper radiator hose goes on the wire color's are black and other one is yellow that should help you to figure that one out.I can't think of another sensor connector you could swap with that one. Even though the check engine light is burned out you can still get code's go to a auto part's store like auto zone and let me know the exact code number's they give you.


Saturntech9
Jan 3, 2011.
The only code that Autozone could get out of it is P0134 - neither rich or lean condition is detected from upstream O2 sensor input. Could that be causing the low mpg and the hestation at higher RPMS(2500 - 3000).


Tiny
Mstanphill
Jan 3, 2011.
So your getting a hestation at higher rpm's?Is it worse with the a/c on?I have never seen a bad o2 sensor reading cause that but that will have to be addressed. Here is the code description for your P0134.I also posted the trouble tree and a wire diagram for that code. Here is the code description.
The oxygen sensor consists of a zirconia electrolyte between two platinum plates. When the sensor reaches approximately 318°C (600°F) it becomes an electrical source that responds to the oxygen content in the exhaust. The PCM produces a bias voltage of approximately 470 millivolts on the oxygen sensor circuit. When the sensor is cold its internal resistance is extremely high, therefore, the PCM recognizes the bias as an open circuit. As the sensor warms up, the internal resistance decreases. When the sensor reaches approximately 318°C (600°F), it starts producing a voltage based on the oxygen content in the exhaust stream. This voltage is used by the PCM to determine a rich or lean signal and adjust the fuel mixture accordingly.

DTC PARAMETERS
DTC P0134 will set if the O2S voltage is inactive (not reading outside 391-491 mV) for 90 seconds when: * The engine is at normal operating temperature (the ECT reads over 60°C [140°F]).
* The engine has been running at least one minute.
* The TP sensor reads over 6.5% (the engine is off idle).
* No other engine sensor or misfire DTCs have been set.
* Commanded A/F ratio is approximately 14.7 to 1.

IMPORTANT: The 025 signal is continuously checked once the above conditions are met.

DIAGNOSTIC AIDS
The PCM will not go into closed loop if a DTC P0134 has failed during the current ignition cycle.

Normal Scan tool readings in closed loop will show the oxygen sensor voltage varying between 1OmV and 999mV

P0134 can set or cause false oxygen sensor readings if the oxygen sensor ground becomes loose or corroded. Refer to PCM and Engine Grounds in this manual.
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Saturntech9
Jan 4, 2011.
Went ahead and changed upstream O2 sensor, cleaned manifold around threads and reset battery. Drove car around for about 60 miles, but still no change in drivablity. Going to recheck engine grounds in morning after motors cools overnight.


Tiny
Mstanphill
Jan 4, 2011.
Does the code come back?Also you never told me if the hesitation is worse with the a/c on?


Saturntech9
Jan 4, 2011.
The ground's for both o2 sensor's are under the intake manifold there tan and held in place by a 7mm bolt.


Saturntech9
Jan 4, 2011.

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