Needs some help with a very random random misfire

[Echo02]

Hello everyone,
I have an 02 Echo ATX with 180k miles on it and thought I would join this forum because it is alot more active than some of the general toyota forums.

The car will drive completely fine with no issues, smooth shifts, pulls till shiftpoint or cutoff. Will drive fine for days and then all of a sudden it will randomly start misfiring. It only starts when the car is thoroughly warmed up, and always appears immediately upon startup if you shut if off. Unless you let a few hours pass. For example last night it was acting up. So for fun I swapped plugs and a used but tested set of coils I have. No change. Left those parts in, started it this morning. It ran and drove fine



If the car sits for a few hours or overnight the issue goes away till it starts again. I pull the plugs each time I try and diagnose it. None are ever fouled or covered in moisture, oil, etc.

I have kind of ruled out a major engine component issue because I would think if it was then it would be a constant thing.

Hoping someone else has had these symptoms and resolved them and can help me. I will pull codes next time it does it. Usually its a random misfire and maybe a specific misfire code.

[CTScott]

Have you ever cleaned the injectors?

[Echo02]

Have you ever cleaned the injectors?

I have not, that was one of my guesses as to the problem and was researching on how to do that last night. The only question I had was would that cause it to misfire, then go away after it cooled down? Because every single time it has done this, sitting overnight or for a few hours causes it to go away.

Do you guys have a good method of cleaning them? because that wouldnt be a bad idea anyway. They are cheap enough new if you get them shipped but Id like to determine that was the problem by cleaning them first.

[CTScott]

I have not, that was one of my guesses as to the problem and was researching on how to do that last night. The only question I had was would that cause it to misfire, then go away after it cooled down? Because every single time it has done this, sitting overnight or for a few hours causes it to go away.

Do you guys have a good method of cleaning them? because that wouldnt be a bad idea anyway. They are cheap enough new if you get them shipped but Id like to determine that was the problem by cleaning them first.

Intermittent lack of fuel flow could definitely cause a misfire.

To clean them properly you really have to either use one of the systems that connects to the fuel rail, or remove them individually and squirt injector cleanser though, while applying 12V power to open the injector.

[Echo02]

Intermittent lack of fuel flow could definitely cause a misfire.

To clean them properly you really have to either use one of the systems that connects to the fuel rail, or remove them individually and squirt injector cleanser though, while applying 12V power to open the injector.

of course, its just the fact that cooling the engine off stops the problem that has me wondering. ill clean them this weekend. Cant hurt.

[Viperoni]

Does it throw any codes?
I get codes for coil packs or plugs almost before I really feel a misfire in my Echo.

[Echo02]

Does it throw any codes?
I get codes for coil packs or plugs almost before I really feel a misfire in my Echo.

Yes! Newer cars diagnostics are so sensitive, mine does that too. About a minute before the shaking and heavy misfire comes the check engine light comes on. From my research it looks like it could be a cam or crank position sensor on its way out.

Yes, I forget the exact numbers and next time it does it I will check but from memory it throws a random misfire and a specific misfire. Almost positive it is not the coils though because I have swapped them for new ones and when the issue arises you can stop the car, swap the coils and it continues, but if you let it sit for a few hours with the same coils it starts and runs fine.

[Echo02]

Well I went to get it emissions tested and all was well until about 2 minutes before the test when I started it to move forward in line. It began to shake. Got the code scanned. Its throwing a p304. Cylinder 4, which I believe is the one closes to the air filter. I guess I will focus my diagnostics on that when i have some free time.

About 5 minutes into the drive home it started driving fine again. Then I had to stop for something and on startup it did it again. Seems to be a trend that after it is driven, shut down and then started again that it happens again.

I reset it and will wait for it to throw a code again and hopefully its a consistant p304.

[YarisSedan]

Missfire is either mechanical / electrical / or fuel related. If the missfire happens when its more under load then its usually electrical such as a coil. One way to test it is remove the coil from cylinder 4 and switch it with cylinder 3. See if it sets a code p0303 then its a defective coil. If it still sets a code p0304 perform a compression test on cylinder 4 to eliminate burn valves or ring issue. At that point with process of elimination you know you have a stuck injector. You could try chevron fuel system cleaner or a bottle of seafoam in your tank and hope for best. Otherwise it will need to be replaced.