Random misfire codes for all cylinders?

JEFF HERMAN

MEMBER
2005 HONDA PILOT
3.5L
V6
4WD
AUTOMATIC
181,000 MILES

All cylinder's random misfire codes, VTM4 disabled when codes are sent. Vehicle runs fine even with every cylinder misfiring randomly. It seems to occur when temperatures outside are colder. There's also something in the engine compartment fuse block labeled IRM19A. There is no mention of this on the fuse box diagram. It appears to be very corroded. Do you know what this is and what it does? Since there are misfire codes on all cylinders and other things occurring are we looking at a bad ECM or possibly broken ground?

8 Replies

JACOBANDNICKOLAS

MECHANIC
108,262 POSTS

Hi,

The IRM19A has me confused. It isn't listed in any of my manuals. Could you take a pic and upload it for me to see?

As far as the random misfire, that can be caused by several different things. First, is a P0300 the only code that is present?

Also, the first thing I would recommend is to check for engine vacuum leaks.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

The reason I recommend checking for a vacuum leak is that all cylinders are misfiring. If it was limited to one, then I wouldn't suspect it. We need to think of things that can affect all of them.

Let me know if that is something you have checked as well as fuel pressure.

Take care,

Joe

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Sunday, October 1st, 2023 AT 10:03 PM

JEFF HERMAN

MEMBER
394 POSTS

Thank you. It is throwing 7 codes. PO300, PO301, and PO306. This is a friend's vehicle so this will drag on for a while as they are very busy, and this isn't their daily driver. I will get a picture of that component. I'll pass the info about vacuum on.

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Monday, October 2nd, 2023 AT 6:08 AM

JACOBANDNICKOLAS

MECHANIC
108,262 POSTS

Hi,

Thanks for the update. When you indicate there are seven codes, do you have the others? Also, don't worry about how long it takes. I'll be here.

Take care,

Joe

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Monday, October 2nd, 2023 AT 7:12 PM

JEFF HERMAN

MEMBER
394 POSTS

The codes are individually PO300, PO301, PO302, PO303, PO304, PO305, and PO306.

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Monday, October 2nd, 2023 AT 9:32 PM

JACOBANDNICKOLAS

MECHANIC
108,262 POSTS

Hi,

I didn't realize they were all misfire codes. I would try what I recommend above. I have a feeling if they are all missing, it is either a fuel-related issue or a vacuum issue.

Let me know.

Joe