O2 Sensors

Callmewhitexr7

Registered User
heres one for ya. my car has been running rich lately leavs black marks on the ground, gas in oil, poor gas mileage. I changed my oil about 100 miles ago and its already black not really black but black. Ok i'm thinking o2 sensors so i bought one cause thats all they had but i pulled the other one out and un plugged it started the car and no cel or anything, why is this and is my problem my o2 sensors?


NICK
 
Callmewhitexr7 said:
heres one for ya. my car has been running rich lately leavs black marks on the ground, gas in oil, poor gas mileage. I changed my oil about 100 miles ago and its already black not really black but black. Ok i'm thinking o2 sensors so i bought one cause thats all they had but i pulled the other one out and un plugged it started the car and no cel or anything, why is this and is my problem my o2 sensors?


NICK
try a search and see if you can find anything. i've read somewhere that a bad 02 sensor won't always cause a CEL.
 
what do you mean black marks? from exhaust? it doesn't sound like a O2 problem, swap the new one with the one from the other side of your car and see if you have the exact same symptoms. its rare for to o2's to go out at the SAME time.you could have anything from a dirty MAF to a vac leak to a bad IAC or a tps not working or out of range. I would start with your intake and make sure all is well on that. you have 4 wires on your maf. disconnect it. one is +12volts and the other is ground. the other 2 one should be around 5volts the other you should get bareley anything. the one you get barley anything is your signal wire. plug the MAF back in and start the car. at idle the MAF should be around .9 votls (give or take). if that is all good, make sure your tps and IAC are in working order...
 
Callmewhitexr7 said:
But wouldnt it throw a cel if i unplugged it while the car is running???
NICK
I would expect it to. The O2 codes are not unique to a running test. They show up as a continuous memory code in some cases, but I noticed that the 2 digit codes for lean and rich are are run test codes. I don't see a 2 digit code for a missing O2 sensor.. :confused: I'd do the running test just to see if it finds anything.

All you need is a paperclip and pencil and paper, provided your CEL is working. Post back if you need details on how to do this.
 
three words: FUEL PRESSURE REGULATOR

pull the vac hose off the regulator and see if there is fuel in it. If there is, the regulator is junk. If not, check the pressure anyway.

As far as the MIL, it takes a little while for the PCM to notice that the sensor is not working. EEC IV doesn't monitor HEGO circuits like EEC V. It will eventually kick the light on, but it might take a while. Be sure that the light works.
 
ok the light works , and already check the fuel pressure regulator, boost leaks, and the IAC is new so how would i check the tps?? and how do i run the codes with a paperclip?


NICK
 
Warm the car up for 2 minutes first. Open the EEC test cover under the hood. Take paper clip (big one) and unfold it and push one end into the SIG RTN pin and the other into the STI lead. Lay it down on a piece of cardboard or something to keep it from contacting the frame of the car. Get in and turn the key on and start the car. Sit back and let the test start. Within 5 seconds, push the brake pedal and let off and turn the wheel 1/2 turn and back. Wait for the single "goose" pulse and press the throttle all the way and let off. Then wait for codes.
If you have a Haynes manual, this is covered on page 6-5. It will read back stored codes first, then run codes. The timing is 1 sec between counts.. (e.g. flash-1secpause-flash would be a 2) 2 seconds between digits (e.g. flash- 1secpause-flash-2secpause-flash-1secpause-flash would be a 22). 4 seconds between sets of codes. A 1 is a pass code.
If you have no problems, 1, 1, 1, 1, 1 means everything is perfect. The middle 1 is a separator between the stored and run code sets.
The codes will be output twice and this takes a bit of practice to get them all.
Good luck.

Here's a diagram of the EEC test harness.
 

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Fuel System Check

Jeremy_K said:
try a search and see if you can find anything. i've read somewhere that a bad 02 sensor won't always cause a CEL.

if there is gas in the oil then i would look at the possibility of open/leaking injectors. use a fuel pressure gauge & check the bleed down time after shut-off to see how quick the pressure drops,then pull all plugs to determine the obvious.
 
bleed down time

what is the normal bleed down time after shut-off? And when you say shut-off, do you mean turning the car's engine off only? because my car says from the codes that it is running lean but under the hood it smells like gas like crazy and there is no power when you push the gas and it is in gear unless you do wot and it is still REALLY slow...
 
how do you check bleed down time and what pressure is it supposed to ba at and how fast should it drop. I may have an injector leak?
 
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