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Old toyota: are cap, rotor, spark plug wires, o2 sensors maintenance items?

I’ve never replaced those and I have about 250K miles on a 18 year old car. I do replace spark plugs every so often. I’ve heard that if the o2 sensor goes it can screw up the catalytic converter very quickly.

If the cat WERE screwed up, would the car still run or would it also need to be replaced? If so, I would think that an o2 sensor would be kind of a maintenance item, ie spend regularly to avoid a huge expense if the converter goes. or maybe catalytic converters aren’t that expensive on this car?

there is no specified replacement interval for oxygen sensors. A few decades ago, there was. On those cars, a warning light would come on at specified intervals, prompting you to replace the oxygen sensor.
On the other hand, I would not hesitate to replace the cap, rotor and wires. You’ve certainly got your money’s worth out of those items!

First off, all those items are maintenance items. Secondly, a messed up cat can damage the car, but only if it gets plugged up. I’ve seen them with the catalyst matrix totally burned out and the engine suffered no ill affects. But, it will never pass emissions that way. Your 1995 Toyota probably only has 1 O2 sensor, so it doesn’t monitor the cat for proper operation like all OBD-II cars made after 1996 do. Therefore, a bad cat will most likely not set a trouble code and cause the ‘Check Engine’ light to go on.

@BustedKnuckles I used to own a 1995 Corolla with the 1.8 7A-FE engine. It actually had a rear O2 sensor. Its purpose was to monitor the cat.
It had federal emissions and WAS NOT OBD 2 compliant. It definitely didn’t have the 16 pin DLC

Thanks. I have an CEL on all the time due to what I was told was a bad EGR valve. It’s been on about 7 or 8 years. If you feather the gas and the engine is warm it’ll knock a bit. But just a bit. Highway miles I don’t notice anything. It seemed expensive to replace and I’m not sure about cleaning it.

There are no emission checks in my state. I still get good gas mileage, so maybe the o2 sensor is still good. I’ll see about replacing it the next time I get the spark plugs changed, etc.

@kenberthiaume sounds to me like a knock sensor code.

I have a 1992 Celica with the 1.6L engine. The EGR was non-functional, but, after testing the EGR valve and valve modulator, discovered the problem was no vacuum from the throttle body. I removed it and found the crud so thick, I could see the vacuum ports in the bore. I used up a can of throttle body cleaner and still had to run a wire through the vacuum ports to clean them out. Now, the EGR works just fine, and it has passed emissions two years straight with only spark plug changes.

I realize that your car has had an EGR problem for a number of years but I would be far more concerned about the EGR rather than an O2 sensor. The EGR is more than an emissions device; it also lowers the combustion chamber temperatures and preventing knocking.

Engine knocking can be engine destroying. Up to this point you’ve been lucky; maybe due to the throttle feathering.