Misfire problem, showing numbers 2 and 3 on computer test

DIANE MILLER2

MEMBER
2003 TOYOTA PRIUS
2WD
AUTOMATIC
182,000 MILES

I have had this misfire issue for about a month or so. 2 oxygen sensors, 4 coils, the mass fuel part, spark plugs have been changed out with Toyota parts. The fuel injectors have been cleaned, but still I get an intermittent check engine light, off for 3 days, then on for 2. Like that. I can feel the rough idle all the time, even when check engine light is off. My mechanic wants to have the head gasket done. My car has not been overheating, no white smoke out of exhaust, no leaking of coolant as far as I can tell, and he has not mentioned it. This last time the computer said 2 and 3. A friend of mine said he should change out the 2 and 3 coils again, in case they were bad ones. He said that if this does not work, then it is the head gasket that needs replacing. I have also seen these sealants, such as Bar's Leaks and Blue Devil that say they can seal any leaks for some time. I believe a compression check is in order, as well as a radiator pressure test, and a chemical test of coolant water, I think called Block Dye tester. Your thoughts on this? I have not had any gas mileage loss. Still getting average 39 miles per gallon, so probably not fuel injectors. Just don't know. Your thoughts, again. Thanks, Diane

1 Reply

JACOBANDNICKOLAS

MECHANIC
108,192 POSTS

Hi Diane, and thanks for using 2CarPros.

Well, the first thing that makes me believe it isn't a head gasket is the fact that compression checks good. Most times, especially if it is bad enough to cause a misfire, you will see compression variations exceeding 25% of each other. If you have the repair slip with the results of what was found, let me know the readings from each cylinder.

Next, I am going to provide you with a link that explains how to check for a head gasket issue. It is easy to follow. The only thing you may have trouble with is the block test. You can do most of this easily at your home.

https://www.2carpros.com/articles/head-gasket-blown-test

If you decide to try these tests, do not open the cooling system until the engine is cold.

As far as your description, it you have any questions if the coils are bad, I would have him switch 2 and 3 coils with coils 1 and 4. If the misfire changes to those cylinders, then the coils are bad.

Based on your description, I really don't feel the head gasket is the issue. However, if you can get me the readings he found, I will know more. There are so many different things that can cause this type of issue. To replace a head gasket that has passed all the tests makes no sense to me. My instincts are making me question things such as a crankshaft position sensor, camshaft position sensor, engine vacuum leak, excessive play in the timing chain (based on mileage) and so on.

Let me know as much as you can specific to his findings on different tests.

Take care,
Joe