P0305 Code & That's the Good News! (Still not fixed though)

[BrianSD_42]

So like the title says I've been having some misfire issues for a while now.

Going back at least a 1.5 years I would get a random misfire code 300, 301, 302, 303.

This seems to happen either shortly after starting the car or after stopping and sitting at idle for a period of time.

Usually only 1-2 of those codes and the truck would never visible misfire (eg no flashing CEL and no miss/power loss. The only noticeable occurance is the CEL lights up solid and my ScanGuage shows the codes.

1st instance I cleared the code and it didn't come back for 6 months.

Then it would happen once every 2 months.

Then before Moab it happened twice in one week. I cleared that code and in the 1500 miles traveled it didn't occur once. But then a week after returning it happened and today it happened twice.

Up until now I have been worried that maybe one of my heads is acting up again. Especially since 301-303 are the same bank/head (I think) and therefore maybe its one side of the engine.

But recently it threw a P0304, and just today P0305 so I'm thinking that is good news and it isn't mechanical which is somehow reassuring.

Anyways I took pictures of the codes, cleared them and drove home without a problem.

Symptoms:
CEL comes on
No power loss
No flashing CEL
No heat issues
No coolant loss

Other:
* Heads were replaced at 199k miles with new JE heads. Ran fine so far.
* Compression test 9 months ago showed no compression issues.
* Plugs and wires replaced a month ago with all OEM


What do I do at this point? I don't want to just start swapping parts for a code that is so intermittent yet it is getting worse. Any suggestions would be welcome.

:bat:

 

[JBurt]

when I was having trouble with misfire codes and no symptoms I replaced plugs and wires which didn't fix it. I cleaned and switched my coil packs around and haven't had an issue since. Might not help but it is easy and free.

 

[19963.4lsr5]

its worth pulling off all the coils and cleaning them and the ignition wires going to the other bank......Thats wasted spark so the coil fires through two plugs to complete the spark circuit.

Did you check the ICM connector at all.........

Did you get my link last night?

 

[lugnuts]

its gonna be really hard to tell specially if its a intermittent random misfire.
i would check your fuel delivery. check injector resistance, compare all six injector. use fuel addictive or pump cleaner gas like shell/chevron.

but then misfire will make your truck run like crap. its possible ecu related problem.

 

[LittleCaesar]

I'd agree with checking the coils first, making sure the boots are good and connected.

How are your grounds, especially the one to the manifold?

Age of the 02 senor(s) or are you a CA with an A/F?

Did this occur before your HID upgrade?

Heat dependent, a la when it is just cold, hot, or does it matter?

 

[BrianSD_42]

Sorry I didn't reply earlier.

Update: the code has been happening at least once per tank, always the same - At idle and once cleared goes away for awhile.

I havent tried any of the suggested fixes yet but will look into it this weekend.

Today I threw 5 misfire codes, all in one instant:

300 (Multiple CYL, I think)
301 (CYL 1, I believe)
302
303
304 (CYL 4, I believe)

How are your grounds, especially the one to the manifold?

Age of the 02 senor(s) or are you a CA with an A/F?

Did this occur before your HID upgrade?

Heat dependent, a la when it is just cold, hot, or does it matter?

* As far as I know ground are good. I really don't know.
* 02 sensors are less than 2 years old.
* Way after HIDs and happens even if lights are off
* Heat does not seem to matter but I guess I would say the engine is warm when it happens (over 10 times now)

 

[Ed_C]

The last number of each code identifies what cylinder misfired. So 301 = cyl 1 302 = cyl 2 etc.
Since the heads have been replaced I'd check the cam position sensor on the passenger side head. Wiring may have have been cut or the sensor is loose.

 

[kball]

So this has been happening since you had your heads replaced? I agree with Ed, check that sensor and also the ground by the diag port on top of the engine driver side. If that's not hooked up all kinds of weird things happen.

You don't feel a misfire at all?

 

[BrianSD_42]

Well I had my head replaced about 3+ years and 25K miles ago.

The problem has only really been happening for the last year and its been intermittent.

It is mainly on the 301,302,303 bank with 303 most common but occasionally it does happen to pop across into the other bank at the same time as well.

Today -at the same instant- when idling at a light, already warm it threw CYL #1,2,3, and 4. In the past it has also thrown 5. I haven't seen a #6 yet though.

I don't feel the misfire because it is always temporary. I guess I would say that it did seem to idle SLIGHTLY rough when it through the code but it didn't die and the CEL did not flash on/off. It just threw the code but kept running fine above idle. I clear the code and keep driving and it doesn't come back for days sometimes. Power feels fine and I've never felt a loss of power when driving.

It has never happened twice in one driving period. So for example if it idles slightly rough and throws code, then I clear it, then keep driving for an hour it doesn't come back.

These symptoms are totally different then when I had a misfire due to cracked head. BACK THEN it was constant running rough (like loss of power) and continuously flashing.

 

[kball]

I was going to suggest maybe the igniter but that's one thing the manual doesn't mention...

There are lots of things it does mention though. I would first check the cam and crank sensors, unplug and plug back in to make sure you're getting a good connection.

 

[LittleCaesar]

How long have you had the CAI on? Dirty MAF?

It could be injector #3, since it shows up the most times. I would think if a sensor has gone south, or is heading that way, you would know it.

 

[topless87]

I would also check to see if you may have a vacuum leak. My upper plenum had a small leak and made my runner have a rough idle, and can make misfire register on a certain cylinder. May be a long shot just what i have expierenced. Good luck. Also check your coils as previous mentioned.

 

[BrianSD_42]

[MENTION=99144]19963.4lsr5[/MENTION]

Thanks. What link, can you resend?

 

[LittleCaesar]

Brian,

I stumbled across this today and thought it may help ya:
Tech Feature: Detecting Misfires in OBD II Engines