Hi.
Was driving my 95 Honda Civic LX (115000 miles) to work this morning when the Check Engine light came on.
Car was not overheating, no obvious problem, oil level fine. Ran all day with no further problem indications, but the Check Engine light stayed on.
What is the possible problems????
Note that have noticed some loss of power in last 6 months, especially when going up a steep hill, and my gas mileage is less than a year ago. Think I got around 45 mpg then, get ~35-40 now.
Have changed plugs and air filter about 10000 miles ago.
Any help would be appreciated.
Could it possibly be the fuel injectors? Can I fix this with some kind of gas additive? Note that I normally use Mobil regular gas.
Just 1 other thing......... I do have a funny clunk type sound that I believe is coming from the front end, notice when go slow and changing gears usually.
Thx.
Bob

txgreasemonkey

Your Civic has probably thrown some codes and that should tell you what is wrong. The clunk sound is probably unrelated and could be bad constant velocity joints. Normally, the front passenger side goes first. If you get this attended to right away, you might be able to repack the CV joint, replace the boot, and be on your way. Get under your car and examine the boots for any splitting. When a split develops, all of the CV joint grease is slung all over the place.

Bob6831

Hi.
Checked my error codes today via pin in the connector. I got a 41 (primary oxygen sensor heater
????) What is this part? Does it make sense with my other descriptions? Note that I have been losing some coolant, may be a radiator leak, but has not been overheating that I can see.
Note that when I turned key on, I get 1 quick blink, did not count that as part of my 41.
Thx.
Bob

txgreasemonkey

This is the oxygen sensor, which is technically called the Heated Oxygen Sensor (HO2S). You will see it upfront on your exhaust manifold.

Disconnect the 8P connector from the HO2S. Measure resistance between terminals A and B on the HO2S. Is there 2-13 ohms? No--replace the HO2S. Yes--Check for continuity to body ground on each terminal on the HO2S. Is there continuity? Yes--replace the HO2S. No--Check for continuity between terminal A and terminals C-H individually. Is there continuity? Yes--replace the HO2S.

8P connector layout:
ABCD
EFGH

Run these tests before we go any further and let me know the results.

Bob6831

Did a check under the hood, and see 1 8 pin connector near the distributor, but cannot get it to disconnect. Is this it, and is there a trick to getting it apart?
BTW, what does this do specifically, and do any of my other symptoms coincide with this part being bad?
Thx.
Bob

txgreasemonkey

That's it. Just follow the lead back from the sensor, which looks like a spark plug going into the exhaust manifold.

Take a small screwdriver and press the release on the connector's mount. Remove the connector from the mount and it will come apart. It takes some getting used to, but it's simple and ingeneous.

The oxygen sensor detects the oxygen content in the exhaust gas, and inputs the ECM. In operation, the ECM receives signals from the sensor and varies the duration during which fuel is injected. The heated oxygen sensor has an internal heater. The heater stabilizes the sensor's output. Therefore, you can see that your poor engine performance could be directly related to a failing oxygen sensor, which is not uncommon.

Should tests prove that the sensor is bad, install a new one and torque to 33 lb.-ft., after applying a pea-size amount of anti-seize compound to the sensor's lower threads. Allow rotation to spread the compound. Apply silicone dielectric grease to the new 8P connector.

Bob6831

Hi.
Got a chance to re-look under hood.
I do see a device looking like a spark plug going into the very beginning of the exhaust pipe.
If this is what you are referring to, it is 4 wires coming from it, with a 4 pin connector going into a wire harness that does have a 8 wire connector further back.
Should I be looking at the closest connection which is the 4 wire one?
If so, what then are the pins you want me to check?
Thx.
Bob

txgreasemonkey

In this type of forum, this is the best I can do:



Why don't you just go ahead and replace the sensor, since you are probably headed that direction anyhow? They cost $59.99 at Autozone, but can save you a lot of money in fuel and greatly improve performance.

Bob6831

Geez........ I do appreciate your help, but don't understand your answer.
The closest connector to the sensor is a 4 wire connector.... hmmmm, maybe a 4 wire in - out connector is a '8 pin connector'? Educate me please.
As far as replacing a part($60) that may not be bad.............???? I do not want to possibly waste money like that if I can at all help it.
Thx.
Bob

txgreasemonkey

Hmmmmm, you obviously have a different engine and a different HO2S sensor. Therefore, spend the money and replace the sensor or wait for someone who's familiar with your engine to chime in with how to test your HO2S sensor. It could be a long wait.