The ongoing saga of P0304 on my 2000 3.4L

Stranger things have happened..

You've double checked your spark gaps?
Again, to rule out anything coil or wire related, I'd drop the gap by 20% from factory spec

 

Yup.....
yes sir...

 

had another poster here, show me a video as we suspect his head gaskets are compromised...
While running the truck after cooling system pressure builds, do you get occasional bubbles in your coolant recovery bottle...
Thats early stages of a compromised head gasket, its not always clear-cut answer inregards if you have a bad head gasket unless you chemical test, pressure test overnight & then boroscope the cylinder & look for coolant intrusion....
do you have the original sparkplug you removed, post a picture of it...
any evident of very faint coolant tint on the electrode?
discolored, dark gummed up sparkplug threads?

could just be early stages & to you, the tale tell signs aren't there yet.

 

I don't have the old plugs but they came out pretty clean. When the check engine light first came on, it was misfiring in 03 and 04. After changing coil packs, the 03 misfire went away. I will take a look at the recovery bottle today.

I am going to test the fuel pump and fuel regulator today. If that doesn't trigger any concerns, I think I have to check the injectors.

 

That was my first thought when I was in your shoes, but injectors are pricey. The job wasn’t as hard as expected and it was very satisfying when the misfire code followed to the new cylinder because I then knew 100% it was bad injections.

 

Well, a very interesting development this morning.

The check engine light is no longer on. Sputtering problems still persist but I don't have a check engine light. The only thing I did between yesterday and today is a compression test which included removing the fuse for the fuel pump. I don't think either of those two things would have cleared the engine code, but all of it's a bit of a mystery at this point.

My plan is to have the fuel pump and regulator check today

 

Is the code actually cleared or is the light just not on?

 

You are correct. My experience with a weak pump or regulator will cause a P0300 not specific to one cylinder.

 

It’s probably soft stored, hence why the light is off. Likely if you plug in a scanner, you can see the code as active.

 

I'm gonna take it in and have them check.

 

What's the current mileage on yer taco, jay
I did not see it mentioned looking through this onceover

 

238k

 

so it sputters all the time while its running & its loaded-up?
or sputter during cold start & then clears up?

if all the time, & you replaced plug & coil, you have adequate compression....
schwag / rolll the dice an injector at it....

 

You should get a OBD II scanner. Something like this one.

$32 Veepeak OBDCheck BLE Bluetooth OBD II Scanner Car Check Engine Light Code Reader, Auto Dual Mode Bluetooth Diagnostic Scan Tool for iOS & Android

https://www.amazon.com/gp/aw/d/B073XKQQQW

 

I had this code. It came out to be my fuel injector connector. the connector clicky thing was broken so when i would drive it would slowly disconnect. Ordered new ones off Amazon and spliced them in.

while youre there you might aswell do your injectors. dont use cheap injectors off ebay. they suck and the orings on them suck as well.

 

I had a similar problem before and it ended up being the wires, even though I had replaced them not too long before. Not saying that's it, but it was for me.

 

So you continue to drive it with a misfire??????????
Thats suicide, you will also need cat converters soon enough if not already....
Raw fuel from the misfire get into the exhaust & overheats the catalyst material....
They melt enough, it will restrict your exhaust....
Cats aren't cheap..

 

I had same issue before also, it was because the spark plug wire wasn't pushed down all the way.
#4 is kinda in a tight spot and when I pushed down on it I can hear/feel it pop in place which would make you think it was seated completely but when I pushed down really hard I hear a 2nd pop. After that no more misfire.

 

Don’t overlook MotorWest Performance when you buy those new injectors

 

What is it pointing to if it sputters during cold-start and then clears as it warms, yet still a bit rough ? I am having this issue w/ a consistent 0302 code.
Also, recently seems to be guzzling fuel & w/ a strong odor of same from engine compartment - gonna change the FPR and see if that helps.