Cylinder Misfire

I’ve recently purchased an 09’ 1500 Laramie with the 5.7L Hemi, it has 183K miles and I purchased it to be a winter truck as well as for trips to Home Depot kind of thing. I’m only planning on putting about 3K miles on it a year and figured it will last me many years with the proper maintenance.

The vehicle has its entire service history documented and visually it’s in great shape. I drove it from Wisconsin to Massachusetts (1,150 miles) with no issues at all, however the next day after getting home a check engine light came on.

I used a “Blue Driver” WiFi diagnostic and it gave a misfire code for cylinder 8 (P0308), but of course when I took it to the dealership they’re telling I need an entire cylinder head replaced for $2,500 with parts and labor.

Thanks but no thanks, the next day the check engine light is no longer on and the truck is no longer idling roughly like it was when the light was on. I’ve driven it 250 miles since the check engine light disappeared by itself and it had no issues.

Does it make any sense that a whole cylinder head needs to be replaced if I got a code for a single cylinder?! Everything I read seems to points to simpler parts replacement.

Also I was using 87 octane with 10% ethanol when I drove it home from Wisconsin and am now using 89 octane with no ethanol. Different gasoline grades available from the upper Midwest to New England. Could the the cheaper 87 w ethanol have caused the misfire? Has it stopped because of me now using the 89 w no ethanol?

Please, any experienced owners or mechanics, your opinions would be greatly appreciated!

First off don't take a out of warranty vehicle to a stealership unless there's no other option. I suggest that you find a reputable local mom n pop shop, I know they are few and far between but you'll have way better chances of not being beat over the head. As for your engine, did they do a leak down test or compression test? Did they explain what happened? Or did they just say you need a new head? I'd get a second opinion and not from a stealership. I'd put my money on the fuel being the issue. JMHO. Good luck man.

P0308 Symptoms

Check Engine Light flashing
Rough running, hesitation, and/or jerking when accelerating
In most cases, there are no adverse conditions noticed by the driver
In some cases, there may be performance problems, such as dying at stop signs or rough idling, hesitation, misfires or lack of power (especially during acceleration), and a decrease in fuel economy
Common Problems That Trigger the P0308

Worn out spark plugs, ignition wires, coil(s), distributor cap and rotor (when applicable)
Incorrect ignition timing
Vacuum leak(s)
Low or weak fuel pressure
Improperly functioning EGR system
Defective Mass Air Flow Sensor
Defective Crankshaft and/or Camshaft Sensor
Defective Throttle Position Sensor
Mechanical engine problems (i.e.—low compression, leaking head gasket(s), or valve problems
Common Misdiagnoses

Fuel Injectors
Oxygen Sensor(s)
Powertrain/Drivetrain problems

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Sykramman,

No, the dealership told me only in passing what tests they did. It was also very quick, within an hour they had already allegedly diagnosed what was wrong. I figured it all sounded too convenient and left thinking just as you did to get a second opinion.

I ran the OBD2 diagnostic again today and it still says it has the P0308 code but there’s still no check engine light and the engine runs without any issues other than poor gas mileage (nowhere near the EPA even with a lot of highway miles and feather throttle).

RoadRamblerNJ,

Honestly if it were not for the poor gas mileage (~14MPG on highway) and the check engine light earlier, I wouldn’t even notice any issues, the engine is running smooth.

There’s a well reviewed Midas in my town, I’m going to take it there Wednesday and get s second opinion. The truck last had spark plugs replaced at 99K miles so it’s time for another. Figure I’ll start there before spending $2,500 on some repair from a dealership.

Thank you very much for both your inputs!

Mendes0311 said:

Sykramman,

No, the dealership told me only in passing what tests they did. It was also very quick, within an hour they had already allegedly diagnosed what was wrong. I figured it all sounded too convenient and left thinking just as you did to get a second opinion.

I ran the OBD2 diagnostic again today and it still says it has the P0308 code but there’s still no check engine light and the engine runs without any issues other than poor gas mileage (nowhere near the EPA even with a lot of highway miles and feather throttle).

RoadRamblerNJ,

Honestly if it were not for the poor gas mileage (~14MPG on highway) and the check engine light earlier, I wouldn’t even notice any issues, the engine is running smooth.

There’s a well reviewed Midas in my town, I’m going to take it there Wednesday and get s second opinion. The truck last had spark plugs replaced at 99K miles so it’s time for another. Figure I’ll start there before spending $2,500 on some repair from a dealership.

Thank you very much for both your inputs!

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If the plugs were done at 99K then they are way over due. The manual recommends every 30,000 miles, yours have 84,000 miles on them. I would replace them and see if that solves your misfire. Could be a coil too.

grizzstang said:

If the plugs were done at 99K then they are way over due. The manual recommends every 30,000 miles, yours have 84,000 miles on them. I would replace them and see if that solves your misfire. Could be a coil too.

Click to expand...

My manual says 100,000 miles for plugs, but then his is way older model. I still think 100,000 is too many.

They switched to the 100,000 mile plugs (platinum) sometime mid to late 2013 model year.

Menéndez, I would pull the plug and check it. Also, other than OEM plugs usually cause issues. If the plug looks good I would move the coil to another cylinder and see if the misfire follows the coil, if it does you have a defective coil.

I,m sure you are aware that there are 16 plugs.

Thank you all for the inputs. The plan is to start with a replacement of all spark plugs tomorrow after doing a compression and leak test. I’ll have them move the coil as well to see if it causes the misfire on another cylinder.

I’ll post an update right after it’s all done tomorrow.

I appreciate all the help, it’s great to see other Ram owners helping!

I have an 09 laramie 4x4 crew with 200k on her. mine did OK on the platinums but is much happier with the copper plugs. especially as you get higher mileage on the platinums. Incidentally that code may be stored but not actually present when you read it a 2nd time. clear them out with your OBD2 adapter after you have done your work.

I would change all 16 plugs to a copper plug. in addition, toss a new coil onto that #8 cylinder. you will have it off anyways so might as well. i have replaced 1 coil pack on my truck thus far. solid normal highway driving I get around 18mpg. ~15mpg combined and with my highway driving over the mountain daily I get around 16.

I also got P0302 on my 1500 2013 hemi 70k miles . That code has been showing on and off for the past couple years. Now it got worse and code stays on. Luckily my powertrain warranty covers it and they gave me a rental.

Dealer says that it could be right side cylinder head, clearance issue, lifters not sealing correctly, camlobe failure or cylinter head.

My truck is currently waiting in line for their engine tech to get to it to start trying the actual repairs... 2 other trucks ahead of me, and it'll take 2 weeks for them to get to mine. Last month, my truck spend 3 weeks at dealership for manifold bolts. Now it's been 2 weeks, and probably will be 2-3 more weeks

Once these trucks starts having issues with lifters etc, they seem to be falling apart and it all goes down hill from there. I already had these similar repairs done couple years ago. If powertrain warranty wasn't there I'd be so screwed... I'm considering selling the truck soon once it runs out. Good luck and to you.

By the way, midas is a chain, they won't know anything about hemi internal engine and won't have experience... so I'd look for reputable mechanic elsewhere. Yelp or Google your local area for keywords such as hemi.

Update:

So I got the truck back from Midas but only drove it straight home to only about 2 miles.

All spark plugs were replaced and the check engine light remains off, as well as the P0308 code is now gone from my OBD2 scanner.

Engine seems to be running smooth. I will drive it around this weekend to see if the code returns but so far so good and a lot cheaper than a cylinder head.

I’ll keep the post updated if I run into trouble over the next few days.

Thank you all once again for the help!

Hello gents.

Just got back from a long weekend up in the Pocono mountains in PA in our 2012 RAM 1500 Hemi with 83k miles on it. Had 61k when I bought it used in July 2016 - loving the truck so far! Truck drove fine on the three hour drive home yesterday late afternoon. Unloaded our luggage and started it back up to park it and noticed a loud tick from the engine bay, first time I’ve heard it. Sounds like the infamous Hemi Tick I’ve heard so much about on this forum.

I got up and drove my son the three miles back and forth to school this morning and still heard it. Got home and backed into the driveway and noticed the idle getting rough. Had other things to do all day during daylight hours. Had time to get back out and start it up this afternoon. Oil levels are fine, first thing I checked.

First thing I noticed is that it would start with remote start but then quit all on its own with a remote start disabled notification. That’s when I first noticed the CEL. I pulled the codes and it’s throwing a P0308 cylinder 8 misfire code. Still have the loud tick as well.

What should I start with? I’m thinking pull the plugs on that cylinder and replace them as a first step.

I need to check manifold bolts as well what with the tick. Could snapped manifold bolts somehow contribute to a P0308 code? Hopefully it’s not a lifter issue as that seems more complex to resolve. Any advice is most appreciated!


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Something to think about on a high mileage vehicle is carbon build up on the valves. This can cause misfires, and poor mileage. I know ford says if a lot of the symptoms listed above persists on a warntied vehicle to just swap the heads as they have no way to clean the valve”s. This could be why ram says they need to swap the heads as well. Just something to think about.