1998 Saturn SL2 has engine light on and the code is ''system too rich'' took to my mechanic he said it was a coolant temperature sensor, plugs and air filter. ok. he replace all those parts and engine light turned on again in about 10 miles. took car back to him and he said it is both O2 sensor. he replaced both O2 sensor. the same thing happen I drove 10 miles and the engine light turned on again. that time he said it was the main computer was bad. the code for the egine light was always ''system too rich''. I took to the saturn dealer and dealer said it was plug wires and the Front O2 sensor was not reading right because it was after market O2sensor. Plug wires and Front O2 sensor were replaced and after driving 50 miles the engine light turned on again with the same code ''system too rich. what do I do?
Possible Causes
The following are malfunctions that could cause a rich condition:
^ Fuel pressure too high. Perform fuel pressure test.
^ Leaking fuel injector(s). - Perform pressure leak down test.
^ Vacuum leak around the MAP sensor grommet.
^ Oxygen sensor contamination.
^ Restricted exhaust or air intake.
^ Fuel Vapor Canister saturated with fuel.
IMPORTANT: If the front oxygen reading voltage is above 600 mV and the rear HO2S is above 600 mV all the time, the O2 sensors are probably not
at fault.
The main computer is probably not bad.
Unfortunately this is a difficult problem to remedy easily, there are many different things that can cause this code.
You seem to be approaching this problem correctly. If the mechanic wants to start changing out parts, ask them why they think the parts are bad. If they can't give you a good answer then you should take it somewhere else.
Unless this is hurting your fuel economy or keeping you from passing an emissions test, I would be careful how much money you stick into a 1998 vehicle.
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Find another mechanic. One that finds out problem and not one that thinks he's going to fix it, if changes enough parts.I would take it back the the dealer, 50 miles and the car is not repaired. its rich, its not a 02 sensor. find out WHY its rich. the first thing you want to inspect is the fuel pressure regulator.
Trouble Code: P0420
Catalyst System Low Efficiency (Bank 1)
Possible Causes:
Air leaks at the exhaust manifold or in the exhaust pipes
Base engine problems (i.e., high engine oil or coolant usage.)
Catalytic converter is damaged, contaminated or it has failed.
Continuous engine misfire conditions, or weak or low coil output.
Front HO2S or rear HO2S is contaminated with fuel or moisture.
Rear HO2S is loose in the mounting hole (check it for a leak).
Front HO2S older (aged) than the rear HO2S (HO2S-12 is lazy) .Here is what is listed in the Saturn repair guide.
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