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1997 RAV4 misfire

A few months ago my 1997 RAV4 developed a misfire. It misfired no matter how long I drove the car (misfire occurred somewhere between 20 and 30 mph). I put fuel injector cleaner in the tank, changed the ignition coil, spark plug wires, rotor, distributor and spark plugs. Changing the distributor cap and rotor (they were only 11 months old at the time) seemed to solve the problem. I did notice that plug #2 had some carbon on it, the other 3 looked fine. Yesterday the problem returned. Code P302 was downloaded (misfire in cylinder 2), a it was several months ago. The difference now is that after 20 or so minutes of driving, the misfire disappears. Its still there when the engine gets to temperature, only time seems to make a difference. I’ve added fuel injector cleaner to the gas again, my question is, is this likely an electrical problem with fuelk inhjector # 2 or is it partially plugged?

Before you do anything else check the compression. Record the actual #s for all cylinders in psi & report.

To learn about an injector you could swap the #2 with another one to see if the misfire follows. But before mucking around too much you check the compression.

I checked the compression this morning with the engine cold. They’re supposed to read 185 or more with a min of 135 acceptable. I guess this is back to #2 fuel injector. Could a few tank-fulls with injector cleaner solve the problem, or is a new one likeley needed?
1: 180
2: 185
3: 190
4: 180

Check the engine temp sensor. Then check the fuel injector. The injectors are normally not hard to fix, it depends on your diy skills. I usually replace them all at once on my own. Pricey but as a diy the labor does not count. My last 6 cylinder cost about 60 per injector with a 10 core per injector.

So should I have them cleaned by a service center, or should I replace #2 fuel injector. I priced them, $129 each.

Ok, I’m starting to rethink this. This morning we had a very mild cool front come through and the misfire was noticeably worse. Would this possibly be caused by a faulty water temperature sensor for the EFI (part #89422-35010)? The temp gauge in the vehicle appears to be worki ng normally.

Are you losing coolant? Does it smoke when you first start it? Smell burnt coolant?

The worsening of the misfire with the arrival of a cool front may be mere coincidence. I would still check the injectors first.

I did add coolant several weeks ago (reservoir was close to empty). I don’t see where it was leaking anwhere. No smoke on startup and no smell of burnt coolant. I’m on my third tank-full with fuel injector cleaner.

Did you check coolant level inside the radiator as well? Not insulting your intelligence, but some people don’t know that filling the reservoir doesn’t guarantee that your radiator is full.

…although on re-reading your posts, it sounds like you do know that :wink: