P0304 error after heat soak

[Serbonze]

So I was out this morning and when I restarted the Jeep after stopping, I got the standard rough idle and stumble common with heat soak. I didn't think much of it, as here in Florida it tends to happen often. However, this time the check engine light came on which has never happened before. I had a few more stops on my way home, and the Jeep didn't have any more heat soak issues, but the check engine light never went off. I checked the code and came up with P0304 -cylinder 4 misfire. I unhooked the battery for 30 minutes then restarted the Jeep and the code was cleared.

Even though the check engine light has never come on before, I assumed that the code would have been for cyclinder three. Now I'm wondering if I should add the insulator to the number four injector too, or maybe this was just a fluke thing.

Any thoughts?

 

[Chris]

Well, my thought is that it wouldn't hurt to add the insulator, since this was actually a TSB from Jeep, when our TJs were still new.

If it was my vehicle personally, I'd treat is as a fluke. If it did it again anytime soon, then I would start treating it as an actual issue.

But FYI, whenever I get a check engine light with no negative symptoms, I always use my code reader and reset it. If it comes back, then I know it's for real. But sometimes they never come back, at which point I chalk it up to a fluke.

 

[Serbonze]

Well, my thought is that it wouldn't hurt to add the insulator, since this was actually a TSB from Jeep, when our TJs were still new.

If it was my vehicle personally, I'd treat is as a fluke. If it did it again anytime soon, then I would start treating it as an actual issue.

But FYI, whenever I get a check engine light with no negative symptoms, I always use my code reader and reset it. If it comes back, then I know it's for real. But sometimes they never come back, at which point I chalk it up to a fluke.

The TSB was for injector three, and I added the insulator for that one last year. For seven bucks, I have no problem adding another insulator to the number four injector. Have you read any reports of heat soak impacting injector four?

I drove it around again today and didn't get a CEL so I'm going to assume it was related to the heat soak.

 

[Chris]

The TSB was for injector three, and I added the insulator for that one last year. For seven bucks, I have no problem adding another insulator to the number four injector. Have you read any reports of heat soak impacting injector four?

I drove it around again today and didn't get a CEL so I'm going to assume it was related to the heat soak.

Ahhh, my mistake. I haven't heard anything about injector four, but it wouldn't surprise me that it could happen, especially in a warm climate like Florida.

Since the light hasn't come back on, I think you hit the nail on the head. In my book it wouldn't hurt to add some insulator to the number four injector.

 

[Serbonze]

I wanted to provide an update for anyone in the future that is researching this. So far I have had no more heat soak issues after insulating injector four (so I now have insulators on injectors three and four), even with some brutal high ninety degree days.