'93 245 w/ 215k miles.

Picked up the Check Engine Light (CEL)w/ 2-3-1 (Fuel system compensating for rich or lean air/fuel mixture at cruise) and 2-2-1 (Fuel system compensating for extremely rich or extremely lean air/fuel mixture at cruise). Replaced the O2 sensor (Bosch) and oil cap gasket. Reset CEL. CEL still comes back on w/ same codes. This morning, I found a little vacuum line that runs from the air intake (at the engine)to down under the air filter box was completely severed. Does this little vacuum line have anything to do with the ventilation dampers in the car? Just to be clear, there are like TWO vacuum lines at the air intake where it clamps to the engine, ..well the one that I found severed is very small diameter and is routed underneath the air filter box at the front of the car. (not sure where it goes).

Anyway...I plugged the tiny line (where it was severed) and reset the CEL. CEL still came back on again with the same two codes. What all could be making these two codes come up? The O2 sensor that I bought had three wires (two white and one black). Does it matter which white wire I connect up? I couldn't find anything marked on the two white wires under the car. Did I mess up the O2 sensor installation? Need some ideas here.

Cabbie

Hi,

Have you cleaned the throttle body lately?

Travis

I fixed the vacuum line leak (to the charcoal canister), found a couple of loose hoses connected to the air tube (tightened)...and then reset the codes. Waa laa. No more codes. (maybe the O2 sensor wasn't the problem?) I think I'm good for now. BUT...

The car slightly hesitates when the INITIAL acceleration from a stop sign. What could make it hesitate?

I'm just happy that after two days of driving, no more codes. I think the air leaks were causing the problem. Can't imagine that I left hoses untightened on the air tube!! The little vacuum line to the charcoal canister must have been part of the problem.

Thanks for all the help. Now to the hesitation-from-the-stop-sign issue.
Cabbie

Check your fuses. I had a similar problem with CEL and code. Replaced O2 sensor and the light came back on. It turned out to be a fuse. The same fuse supplies the fuel pump (in tank I believe). Replaced fuse and no problem since. I got the information from someone on this site.

Randy

93'240 Wagon, 130,000

check the fuses - there is a fuse for the o2 sensor.

Also, you can check the function of the o2 sensor easily if you have a multimeter (voltmeter). Start the car and let it warm up to operating temp -Dont disconnect the o2 sensor lead (at the firewall) - but peel back the rubber insulator so you can probe the connector with the positive lead of the multimeter - ground the negative lead of the meter to the battery neg. post. You should see the readings fluctuating between .250 and .750 volt every couple of seconds. If so, your )2 sensor is working fine. If it gives a steady reading around .4 - .5 volts and/or only fluctuates slightly then its bad.

Where's the connector at the firewall located? Is it near the battery? I just bought the new O2 sensor....so I only suspect that it may not be connected properly. The test you recommended will show if I connected it up correctly?

That line goes to the charcoalo evaporative canister (both lines go there).
If one was broken, bet the others are chracked and broken, also.
Check the corrigated intake hose, flame trap hoses, idle air control bypass hoses for leaks, as well as the intake manifold gasket. It's probably a good time to replace every hose if they are original.
That code doesn't necesarilly mena the O2 sensor was bad, most often is vacuum leaks, Replace the sensor only after you know the leaks are fixed.

I've already replaced the O2 sensor. There are several hoses (as you've mentioned).... I suppose I can take them all apart and look for a cracked hose. What's that charcoal canister thing supposed to do?

Hi,

What was the brand and model # of the O2 sensor?

I think the hose you are speaking of goes down underneath the left corner of the car and connects to the charcoal canister, which is part of the Evaporative Emission Control system. Both of the hoses up their on the throttle body connect to it.

I'm not sure though if the cut off hose would be enough to set any codes.

Travis

If these hoses are not connected on both ends there will be an air leak into teh intake and throw the code. The lines pull vacuum on the entire fuel system including the tank. Replace them.

The O2 sensor I installed was a Bosch part # 15725 (little numbers 0258005725D09). It screwed right in near the cat converter. It had 3 wires: two white and one black. The two white wires were not marked (on the old O2 sensor nor on the new one), so I wasn't sure which white wire went with which.. does it matter?

So you screwed the new O2 in the exhaust pipe and plugged it into the harness on the firewall?

Did you buy a 'Universal' O2 sensor and splice it into the old wiring harness?

The universal one's are (can be) garbage, and fail for any ONE of these reasons:
1) Incorrect sensor for your car
2) Poorly spliced into the old wiring harness
3) Soldered into the old wiring harness
4) Incorrectly wired into the old wiring harness
5) Correctly butt-spliced with crimp connectors into the old wiring harness with insulating sleeves, but old harness connnector and/or wire is 20 yrs old and corroded and toast. Anything blocking the air from the connector to the sensor through the harness will keep it from working properly.
6) Pinched or skinned wire insulation, even slightly squished insulation will keep it from working properly.
7) Slow response from new sensor even though everything above was done correctly, but your too much of a cheapskate to buy an OEM fit O2 sensor.
8) The old sensor was fine but you didn't fix the vacuum leaks yet
9) All of the above

If so then go and buy one made for your car and PLUG it in. Sometimes saving money is done by spending it in the first place, like getting all new vacuum hoses and not just the one's you can see are bad.