Engine Light Came On

[SHOracer14]

I noticed about a month ago that the car was idling a tad high and was making a sort of ticking noise. I didn't think much of it until the check engine light started coming on periodically. If I throw some revs or run it hard for a minute or two the light goes back off. I checked the codes and got a 92. With these symptoms I diagnose bad oxygen sensors. Is this a correct assumption?? I know that it can't be dirty intake problems because I had the intake off and cleaned everything when my tranny was done a few months back. Another weird thing is I threw in some injector cleaner and reset the idle. This fixed the problem for a few days (and even made the tick go away) but it then returns.

 

[Rockledge]

Just a thought, but you might want to think about the T-stat sticking open or maybe a bad ECT sensor, which would lead to cooler engine temperatures, which in turn would cause computer to run in rich mode more often than it should.

 

[rangerj]

SHORACER,

Lets take your diagnosis a little further. The code 92, in the running condition indicates that the left (front since the engine is transverse mounted [right Steve?])O-2 sensor is signaling a rich condition.

If you had a thermostat stuck open, or a faulty coolant temperature sensor, why would only one
O-2 sensor indicate a rich condition? Why not both?

Next, the ticking noise. Have you listened to your fuel injectors? Listen to them with a mechanics stethescope, or a screwdriver (point to the injector and the handle to your ear)and listen for any unusually loud "clicking".

You could have a clogged injector that is not closing as much as it should and causing the rich condition. Pay close attention to the left bank (front of the car) of injectors.

The O-2 sensor has a good connection and is sending a signal, otherwise you would not have the code or CE light. If the code indicated that the sensor stopped switching I would agree that the sensor is most likely failing.

You could also pull the left bank plugs and look for the rich condition, that is a black carbon build up in the tips of the plugs. If one plug is rich, then that is the injector to suspect.

If your O-2 sensors are more than 50K to 75K old It would not hurt to change them. What condition are your plugs and plug wires in? A blackened plug could also indicate a failure for the plug to fire, or have a weak spark (possibly wire or coil).

My final point is that when a sensor codes it very often does so because it is providing correct information, unless the code indicates a lack of a signal coming from the sensor. When that happens it is either a bad sensor, or a bad connection.

Look for anything that would contradict the information that the sensor is feeding the computer, for example if the coolant temperature sensor is telling the computer that the engine is cold, but you know that it is fully warmed up.

So if your O-2 sensor is telling the computer that the engine if rich, but there are no signs of a rich running condition, then the sensor is failing. The O-2 sensors usually stop "switching" or the switching slows down when they are failing. That is why I am hesitant to condem your O-2 sensor without some further investigation.

Just some thoughts, rangerj