Please don't laugh - O2 sensor dreams

[tgerhard]

Hello all,

Backstory: I have a 1995 Corolla that I dearly love but has been a non-moving fixture in my driveway for the past year. Before that, my mechanic had it for about six months because one morning it simply stopped running. A new fuel pump relay, new distributor and coil got it running again, but extremely poorly -- frequent but intermittent hesitation and missing and often stalling out completely. (However, it would start right back up.)

After reading threads on this forum, I tried simply replacing the PCV valve (something the mechanic had not done). Voila -- started her up, drove her around -- wonderful. But only for about 15 minutes. The previous symptoms appear only after it warms up. Since then, I've not driven it anywhere, just start it up every now and then.

The dream: With some vacation time coming up I finally have some time to work on the car. Last night, I had a dream that I got an O2 sensor in the mail, installed it, and it fixed the car. I must have read about this somewhere, but don't recall. It was an extremely vivid dream.

Question: I normally don't give credence to dreams (I'm a data analyst, and equations have to add up in a spreadsheet for me to give them any value.) However, with what has been done to the car so far (it is getting gas and spark), is an O2 sensor a reasonable fix? If so, how difficult is it to replace an O2 sensor in this model?

Many thanks for any and all suggestions.

Tom

[ganda1f]

Given that the symptoms come back once it warms up, it sounds like something is wrong when the engine enters closed loop operation. Typically some sensor feeds false readings to the ECU. Faulty oxygen should set an error code.
Your car being a 1995 likely has an OBD1 ECU, meaning that you can check trouble codes w/o a scan tool.
Jumper terminals TE1 and E1 in the diagnostic connector in the engine bay. Turn on the ignition, do not start the engine. Look at the Check Engine Light (CEL) in your instrument cluster. Continuous fast flashing means no code is stored.
Otherwise count the flashes.
Several flashes (first digit), short pause, several flashes (second digit), long pause. This is one error code. If there are more, they will follow in the same manner, and finally the codes will be looped over again. If there is just one code, it will flash over and over again. Oxygen sensor related codes are 25, 26 and 27.

Personally, I would suspect the coolant temperature sensor. If it feeds wrong info to the ECU it will mess up fuel delivery quite badly. The temp sensor should have 2kOhm resistance at 20 degrees Celsius (68F) and some 180-200 Ohm in 100C (212F). I posted a full table some time ago.

Further, you can check the oxygen sensor in the following way:
Warm up the car, jumper TE1 and E1, connect an analog voltmeter (you need to see the needle fluctuate) to VF1 and E1 terminals. Have someone keep the engine revs at 2500rpm and check how many times the needle fluctuates in 10 seconds. It should be minimum 8 times.

[speedy25]

Distributors are supect too. Even new ones. One member of the forum finally fixed his car by removing the new one and installing a used one.

99% of the time heat related problems are electrical, but finding the right piece that is affected can be difficult. Keep at it.

-SP

PS- I have had solutions to mechanical problems appear in my dreams that I would never thought of with a wrench in my hand. Its not as crazy as you may think.

[jelly53]

im thinking it might your catalytic converter. take it out and look inside, it might broken lose and its messing up the air flow.