What's wrong with my Hemi?

Post by **DamageWagon** » Sat Dec 17, 2016 1:22 am

Hey guys, I would post this on ram forum but I would rather ask here first.

I have a 2011 Wagon that I bought a few months ago with a known misfire problem. I made a lengthy list of possible problems and troubleshooting tests but they have gotten me nowhere.

Symptoms: when the truck is about 150F or warmer the misfire can happen. It is occasional and of varying degrees of shaky. Maybe twice a week it will misfire. Never when cold or early in warmup. Otherwise it can be during normal running, after a cold start, hot start, wet weather, dry weather - nothing changes it. The most common way to emulate it is aggressive parking lot type driving, frequent on and off the throttle and brake. It gets reeeeally bad if I just lightly hold the throttle, it roughly holds 800rpm but is really rough. The rpm hunts about 200rpm either direction when I hold steady throttle. BUT if I bring the throttle over 2500-3000rpm and hold the throttle steady, it will slowly take steps up in rpm and then will smooth out and fix itself, and when I let it go back to idle it is smooth. Also, the truck can be misfiring at one street light, as soon as I start driving and get the RPM's above 1000 it drives smooth, and after I go 1/8 mile to he next light it will be running smoother than butter. Normally the truck runs a little bit rough, like a 5.9 cummins when it is at idle.

I have had a cylinder #2 misfire and general cylinder misfire code flashing during a few of the misfires, but it's not just a single cylinder. I pulled the fuel injector wires during one of the misfires and each one made it worse but every one had an effect, so there was no dead cylinder.

I'm really thinking there's nothing mechanically wrong, it has to be electrical/sensory. It has brand new MSD cool packs, brand new OEM plugs, all spark plug and injector wires look good, I replaced the Crank and Cam position sensors. No changes whatsoever.

I REALLY feel like this is an oxygen sensor problem because it seems like the misfire can be occurring starting at the split between the cold loop O2 programming ad the warm loop O2 programming (my understanding is that the O2 sensors are ignored until a certain temperature). The cats have been covered in a layer of mud for years now, I think maybe an O2 sensor has cooked but there are no DTC's for O2 sensor issues.

Also I have DTC's for minor and major evap system leaks. I replaced the gas cap with no change. Will be getting it smoke tested soon. Don't know if this could be related?

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YouTube · Post by **OffroadTreks** » Sat Dec 17, 2016 1:39 am

When did you last change the spark plugs on that 5.7l Hemi?

Post by **DamageWagon** » Sat Dec 17, 2016 2:01 am

A month ago/2000 miles

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Retired BLM Rig · Post by **Retired BLM Rig** » Sat Dec 17, 2016 3:38 am

I would focus on getting your evap codes cleared first, especially if there is a "major" leak as you state. When the evap purge solenoid opens, the computer is expecting a certain increase in fuel vapor entering the engine from fuel tank fumes/evap canister. If you have a large enough leak and it's drawing straight air and no fumes, it may be a lean misfire that you're experiencing. Usually the purge cycle occurs on a warm engine, not cold. A scan tool with live data would allow you to monitor short term and long term fuel trim when the misfire is occurring to help determine the cause. A cheap test would be to locate the evap purge vacuum line at the engine (usually has a green capped Schrader valve test port somewhere inline) and cap it off and drive it for a couple days and see if the miss is still there.

Other options:
Do a compression test on all cylinders to confirm normal or borderline weak cylinders.
Install a vacuum gauge to check for a possible sticking valve.
Inspect for a broken valve spring.
Possible intake manifold gasket leak, allowing unmetered air to enter the engine (lean misfire).
Check for bad ground connections on the engine and all around in the engine compartment.
Check with the dealer to see if there's a computer reprogram that needs to be done that might solve odd issues.

Trust the computer to tell you what's wrong with the truck and start there. Don't spend any money on oxygen sensors unless you have hard evidence/codes pointing you in that direction.

Retired BLM Rig · Post by **Retired BLM Rig** » Sat Dec 17, 2016 3:58 am

Also, if you have a misfire code to a specific cylinder (P0302 = #2 cylinder misfire), try swapping the coil and plugs from that cylinder to another one, to see if the code follows the components. Compare the appearance of how the plugs are burning when you switch them.

Just my .02¢.
Good luck.

Post by **DamageWagon** » Sat Dec 17, 2016 10:27 am

Thank you, those are all really good suggestions. The old plugs looked to be a little lean. I don't know if that's normal on these engines?

I have swapped coil packs with no change. I cleaned the MAP sensor and PCV valve and throttle body. I sprayed brake cleaner around the intake manifold to see if idle changed, but it had no effect.

I will try your idea on the vacuum line. I think if that does not work I will get it smoke tested to see if we can find a leak.

I think I'll take it to a dealer to check for updates too, I don't think it's had one in a long while.

If these tests don't work I will go down your list to the other items.

I appreciate your answers, you might end up saving me some coin and a lot of frustration

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TwinStick · Post by **TwinStick** » Sat Dec 17, 2016 10:36 am

When i replaced distributor cap & rotor & the factory coil with an Accel coil on my 88' Ford Ranger, I had all kinds of miss fire issues. Replaced with another new Accel coil. Same thing. Put a new Ford part on there & it ran fine. A mechanic said maybe the Accel coil was just putting out too much spark ? Kept burning up distributor & rotor. The whole weakest link kinda thing. I always used ford coils after that on that truck & had no more issues. Weird.

I think someone else had this issue a while back & it had something to do with the evap canister that is underneath by tank somewhere.

Post by **DamageWagon** » Sat Dec 17, 2016 10:41 am

TwinStick wrote:When i replaced distributor cap & rotor & the factory coil with an Accel coil on my 88' Ford Ranger, I had all kinds of miss fire issues. Replaced with another new Accel coil. Same thing. Put a new Ford part on there & it ran fine. A mechanic said maybe the Accel coil was just putting out too much spark ? Kept burning up distributor & rotor. The whole weakest link kinda thing. I always used ford coils after that on that truck & had no more issues. Weird.

I think someone else had this issue a while back & it had something to do with the evap canister that is underneath by tank somewhere.

That's interesting. I was worried that the last owner replaced the coils with MSD instead of factory. He did this right before I bought the truck, but he said it didn't change anything. I still have the factory coils.

I have heard the little evap pump bolted to the canister can go out and cause issues with trouble codes. I might just replace it, that's a cheap part and there's no way to test them I think. Are you saying though that an evap canister problem has caused engine issues?

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Ducky's Dad · Post by **Ducky's Dad** » Sat Dec 17, 2016 4:26 pm

This is a stretch, but I'll throw it out there anyway. Recently had a similar problem with a high speed miss on my 5.7 GMC Vortec. Truck was throwing the occasional code, intermittently, on both banks. Lots of intermittent misfire and stumbling at highway speeds, transmission hunting for gears and not kicking down without flooring the throttle. Took it to a professional and he found low voltage at all four 02 sensors on his reader. His solution was to pull all the weatherpack connectors to the computer and add a liberal amount of dielectric grease to the plugs, then reconnect. Bingo! Problem solved. I never would would have figured that out on my own.

coder · Post by **coder** » Sat Dec 17, 2016 9:29 pm

Hello DamageWagon,

Sorry to hear about your engine troubles, it might be worthwhile to take it to the dealer for a diagnosys then fix the problem yourself. It will probably cost you an hour labor's but it's often cheaper than throwing parts at it. Good luck!

Post by **DamageWagon** » Sat Dec 17, 2016 9:54 pm

coder wrote:Hello DamageWagon,

Sorry to hear about your engine troubles, it might be worthwhile to take it to the dealer for a diagnosys then fix the problem yourself. It will probably cost you an hour labor's but it's often cheaper than throwing parts at it. Good luck!

You very well might be right. I really am not considering going to the dealer because I've been through so much troubleshooting already that I doubt they will have anything new that isn't also on the list of things to still check, unless it is something that is too expensive for me to pay them to check anyways. They might know exactly what is wrong and have a fix that could save me a lot of time and money and energy

it's the thought that they could be complete idiots that take my truck away for 3 days and charge me hundreds to look under the hood and find nothing that keeps me from ever considering a dealership... I'm biased, and I know it. Maybe if it gets to that point, I will take it in.

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Ducky's Dad · Post by **Ducky's Dad** » Sat Dec 17, 2016 10:25 pm

The dealer scanner can see codes that you won't pick up with a $10K Snap-On scanner.

Post by **DamageWagon** » Sat Dec 17, 2016 10:43 pm

Ducky's Dad wrote:The dealer scanner can see codes that you won't pick up with a $10K Snap-On scanner.

I never thought about that. We used one of the nice Snap-On scanners a few times but it makes sense that the people who made the codes would have more accessible than the company that had to find them and put them into their products. Thanks!

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flattire · Post by **flattire** » Sun Dec 18, 2016 1:44 am

When I started reading your symptoms for some reason O2 sensor came in my head. There is a failure mode that may not set off a code but could result in poor driveability. Known as a "lazy" sensor. A good sensor switches from about .2 volts to about .8. This switching causes fuel delivery to go from rich to lean in a cycle. A tired sensor may not reach these limits or just move slowly rather than rapidly. A dirty connection may also be an issue.

Scan tool can read o2 values as they change and may be of some help. Maybe even check connectors on sensors and clean .

Post by **DamageWagon** » Sun Dec 18, 2016 3:11 am

I don't think it's connectors based on the symptoms. Could be, but I'm led to think otherwise. One reason I think O2 sensors is that the exhaust system has been covered in mud for years, and I know that the added thermal insulation will hurt the sensors over time. O2 sensors live in a hot environment but once the sensors and cats get hot enough they start to fail very fast.

Drive ability is consistent though. I don't have a baseline, I've never driven another 5.7 but I assume it drives normally. It drives just fine once it's over 1000rpm.

One weird thing that just happened last night for the first time was that while I was driving home from work o noticed the exhaust started to sound really weird. It sounded really deep and resonant out of the blue, like it has never sounded, as if I was driving through a drive-thru. I pulled over and checked it out and it was running a little rough but not the worst I have felt it. The sound slowly improved back to normal. I started driving again, and it was running rough at the first light where I stopped. By the time I made it to the second light it was running the smoothest I have ever felt, no kidding. I didn't know my engine could run that smooth, I'm so used to it always feeling a little rough.

Does everyone else's engine feel smooth at idle?

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Retired BLM Rig · Post by **Retired BLM Rig** » Sun Dec 18, 2016 4:24 am

My engine runs so smooth, sometime I have to look at the tach to see if it's still idleing.

The company I work for subscribes to a diagnostic database called Identifix. Thousands of professional technicians throughout North America use it and add data to it on a daily basis. For really weird problems I can log in and type in keywords, symptoms or codes and it gives me back a list of known problems, factory technical service bulletins, recalls and confirmed fixes that other technicians performed that solved the problem. It's an awesome resource to help the independent guy keep up with all the latest changes. Anyone can use Identifix, you don't have to subscribe for a whole month. You can call their technical hotline, describe your symptoms and diagnostic results so far, not feelings or what you think it is, but actual diagnostic data (compression, fuel pressure, voltages etc.). For $39 they'll point you in the right direction to proceed with your diagnosis & repair. If you have to call back a second time on the same repair, the price goes down with each call.

I entered the data for your truck and the keyword "misfire". The most common fixes by far, after spark plugs and ignition coils, were broken valve springs and camshafts going flat on one lobe, not opening the valve far enough to get fuel in or to get exhaust out. I've personally seen valve springs that were broken in just the right place, so that the valve would still close, but not tight enough to completely seal it every cycle. It even tested good on a compression test. If it comes down to pulling a valve cover, make sure to use a mirror to look around the entire circumference of each coil on each spring (it's easy to miss). Make sure to focus on the cylinders with the misfire codes, but check them all. If everything looks good there, compare the valve action of each cylinder as the engine cranks over, to look for a worn cam lobe.

Good luck!

Post by **DamageWagon** » Sun Dec 18, 2016 5:16 am

Thanks man, that's good to know! I don't think it's the cam because it is hit or miss, but it could be valve springs maybe? I really don't think it is but I could be wrong.

I'm open to pulling valve covers though

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FirerescuePW · Post by **FirerescuePW** » Sun Dec 18, 2016 12:42 pm

My exhaust has a deep, resonant sound right after start-up, when it is in the cold loop. Is it possible it is drifting back and forth between hot and cold parameters? If so, would this show up with a real time scan?

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Post by **DamageWagon** » Sun Dec 18, 2016 12:45 pm

FirerescuePW wrote:My exhaust has a deep, resonant sound right after start-up, when it is in the cold loop. Is it possible it is drifting back and forth between hot and cold parameters? If so, would this show up with a real time scan?

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That's an interesting thought, I didn't think of that. I wonder what determines which loop it is in? Is it the temperature sensor?

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Retired BLM Rig · Post by **Retired BLM Rig** » Sun Dec 18, 2016 7:04 pm

Oh no... Here comes another one of those long, boring technical posts by that BLM guy.

DamageWagon wrote:
FirerescuePW wrote:My exhaust has a deep, resonant sound right after start-up, when it is in the cold loop. Is it possible it is drifting back and forth between hot and cold parameters? If so, would this show up with a real time scan?
That's an interesting thought, I didn't think of that. I wonder what determines which loop it is in? Is it the temperature sensor?

The technical terms are "Open Loop" (cold) and "Closed Loop" (warm/hot).
Open loop is when you first start the engine and the computer isn't receiving data from sensors yet, so it's just running on preprogrammed information from the computer software.

Closed loop occurs primarily after the oxygen sensors have warmed up and begin providing feedback data to the computer. Try to think of the oxygen sensors as the nose for the computer and they're constantly sniffing the exhaust to determine if it's too rich or too lean, then the computer uses that information to control fuel trim/injector pulse width. The computer is trying to maintain the perfect 14.7:1 air/fuel burn ratio to produce the lowest emissions.

An oxygen sensor has to reach 500-600º before it starts working. Back in the 80s O2 sensors had one wire and relied on the heat of the exhaust to warm it up before it could provide feedback, which could take minutes. Now O2s have 3-4 wires with a built in heater to warm it up as quickly as possible so they begin to provide feedback in under a minute. Closed loop is when the computer is making live control decisions based on live input data.

Our engines have four O2 sensors, one for each bank of cylinders before each cat, sniffing raw exhaust and providing primary fuel mixture feedback and two more sensors after each cat to monitor the efficiency of the cats doing their job.
The O2s are critical to the proper function of the engine, so they are constantly being monitored for errors. There are 30-40 generic codes for identifying errors and turning on the check engine light just for the O2s (slow/lazy, dead heater, high volts, low volts, shorted, etc.).

Yes... a good scanner will tell you in real time if a computer is in open or closed loop and allow you to view live O2 data for each sensor. It is possible for a computer to slip in and out of closed loop, but there's a code for that too. Enough about loop status and O2 sensors. Moving on.

Modern vehicle computers are so sensitive they can detect a misfire or even a weak cylinder before it's humanly possible. If the computer senses an intermittent misfire has reached the point that raw unburned fuel is entering the catalytic converter, it may shutoff the injector for that cylinder to save the cat from overheating damage. If this happens, usually the check engine light will go from being on steady to flashing to really try and get the driver's attention. An engine misfire could cause the computer to go into open loop, because the computer knows that there's unburned oxygen skewing the O2 data, so it has to abandon live data and resort to open loop programming. Again... focus on the current codes that are stored in your computer and try not to get sidetracked by the what ifs. Good luck!

Ok... resume normal posts.

w2dodge · Post by **w2dodge** » Mon Dec 19, 2016 11:36 am

had a same issue with my 4.7 jeep..misfire cylinder code..truck i bought brand new..had 30xxx miles on it at the time of this issue...turned out to be fuel rail was corroded inside...clogged..luckly it was under warranty

cruz · Post by **cruz** » Mon Dec 19, 2016 11:48 am

Retired BLM Rig wrote: Again... focus on the current codes that are stored in your computer and try not to get sidetracked by the what ifs. Good luck!

^^^... Great advice.

Will · Post by **Will** » Mon Dec 19, 2016 12:35 pm

First thing I would do is take the MSD coils off and put the factory coils back on. Disconnect the battery before doing so, change the coils and let it all reset and try it again with the factory coils. It should not run rough, like said above, I've tried to crank mine while it was running, if that tells you anything.

Post by **DamageWagon** » Mon Dec 19, 2016 12:36 pm

Thanks for the advice guys, it has been solid.

I'm thinking there are codes in there that are not showing up like has been said. I will have rough running and even blatant misfires and it will not trigger the CEL. A few times though it did trigger the CEL and was flashing. I'll try to get my emissions codes taken care of and then proceed from there. Minor and major evap system leak is what the codes are
0440
0456
0457

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TwinStick · Post by **TwinStick** » Mon Dec 19, 2016 7:36 pm

Minor evap leaks are usually the gas cap.

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