The dreaded random misfire code. Anyone ever had enough experience with this code to know what is the most common problem? It has come on a couple times then goes away but cruising down the highway I can feel a slight jerk every now and then and notice a slight change in the rpm when this happens. I’ve changed the plugs and I believe the coil packs are okay cause i disconnect one at a time and notice the engine starts missing. I’ve cleaned the throttle body and checked the egr valve and seem okay. I listened to each fuel injector and they sound good and checked the ohms resistance on each and they all show about 13.1 to 13.2. Would this test on the injectors mean it is spraying fuel like it should though?

What vehicle?
I believe my buddy had the same code chased it like you, landed up being a small vacuum leak.

02 Isuzu Rodeo with the 3.2 v6

Actually I cleared the code the few times it’s came on and hasn’t come back on in awhile except the other day it threw that code but I had just sprayed a bunch of throttle body cleaner in it and figured that caused it cause hasn’t come back on but still jerks. Last couple mornings on way to work the check engine light flashes all the way, then no light when coming home. I know you’re not supposed to drive with a flashing check engine light but at this point I’m hoping it does something to give me a better clue.

We bought this from my wife’s best friend, she bought this car brand new and only put 54,000 miles on it and I bet 90 percent of those miles are in town. She did have regular service on it and the car looks almost brand new. Kinda rare for a Midwest car.

Should mention the check engine light stops flashing when I let off gas and coast. Just started it now at home and it flashes but comes and goes while holding it at 2000 rpm’s which is about where it runs on highway. I thought maybe it was just like me and hates going to work but I was wrong lol.

Just wonder if dampness would have anything to do with it? Does it in the morning then sits at work for bout 10 or 12 hours and light stays off on way home.

Fuel filter ? Recently changed one on a 03 car that only has 50,000 miles and was only dring occassionally in town and the filter was full of black crap.

that is what I was wondering I know we were in the 40s the last few mornings

do you park inside at night?

could you to see it it changed anything?

did a little looking 2000rpm seems to be the common place itis noticed

a variety of issues , many found a vaccum leak , a few found no vaccum leak but replaced all the plugs and found a bad plug and it fixed it

https://www.planetisuzoo.com/threads/random-multiple-misfire-p0300.83726/

possible if you had a cracked porclin on a plug it gets damp over night but dry as a can be by the time you drive home from work

I’ve changed the fuel filter and still does it. Messing with it now and looking at all the vacuum lines I pulled the vacuum line off the fuel pressure regulator and gas poured out of it. Don’t think it should do that.

No it shouldn't, if fuel comes out of the vacuum line, then the regulator is leaking and needs replaced.

Correct, you probably found your problem.

Took regulator off and there should be a small O ring on that bottom nipple but no where to be found. Some where along the way the someone had this off because the 2 bolts that held it on are Allen heads and the one that’s a bear to get at had a regular bolt put back in.

The air filter compartment reeks of gas also

That looks exactly like a GM regulator. Replaces countless ones that were in vehicles running "reformulated" gas.

I'd replace the regulator and the air filter.

GM actually used torx head screws.

So the o ring was actually there it was still inside. That is part of regulator still stuck in the housing.

Took the wifey in it to get ice cream bout a 50 mile round trip and runs like a champ now.

Could be a head gasket leak into one cylinder. If they didn't change the coolant on a regular basis and it turned acidic it'll eat the gasket up. Gives you that 0300 code.