I'm starting to go through RAM withdrawal, my 2010 4x4 Big Horn has been at the dealer now for 8 days and they tell me they have no idea why its misfiring on #2. Todays answer is a Chrysler engineer is working on it no further information, which was their story 2 days ago.

They keep changing their story which is getting on my last nerve. After the first round of diagnosis they moved the injector to another cylinder and the mis followed the injector. Sounds reasonable that its the injector right. They said they tested all the injectors and determined that one was bad and another was dodgy so they were going to order parts and have the truck back to me in a few days.

Story changes...so a few days later they say I can come pick up the truck. I ask if they changed the injectors, no they said. Supposedly they tested the injectors a 2nd time and they were fine. Then they said Chryslder determined that the problem was carbon build up on the back of the valves disrupting the air/fuel flow. They say they decarboned it and it improved so they decarboned it a 2nd time and that cured the misfire. Bad gas they said.

I called BS on that, what did the carbon build up on valves just magically jump over to the other cylinder when they swapped the injector and the miss followed the injector? Idiots, jeeze.

So I pick up the truck and its still misfiring, you can feel it in the seat, at the tailpipe, but no check engine light and the service people were gone for the day so I drive home. I didn't make it out of the driveway the next morning and the check engine light was back on.

So its back at the dealer now. I think they just sat on it the past 2 days and did nothing from the sound of it. Meanwhile I'm driving a junker dealer loaner Mercury Milan tin can. Ahaha I'm actually embarrassed to be seen in that thing! lol

I'm being nice for now but very soon if they don't get off their *** I'm gonig to go nuclear on them.

 

Mercury Milan a trade-in? Thats a nice car believe it or not for them to rovide as a loaner! Most dodge dealers stick you in a caliber or a smaller car, not even a midsize!

I'd say they didn't touch your truck and just did a fuel injector service. It's alot of work to move an injector from one cylinder to the next! They could have possibly moved a coil pack from one to the next though???
You could have a further issue such as a head gasket ptoblem although I don't think this is the case. Hemi's ar pretty good in that dept.

They need to do a compression check and a leakdown test. This will tell them if the valves are operating properly and if there's an issues with broken ringlands on the piston(common problem when using 87oct) 87oct that has 10% ethanol can be very detrimental if it's been sitting in a gas stations tak for longer than 3weeks. It'll suck up any water molecules and ruin the octane rating of the gas. So, bad gas could be the cause...

 

They did a compression test and said it was fine. They also tested the coils and said they were fine and they changed plugs in that cylinder. I run only 89 octane. Speaking of which, get ready...wait for it...the service manager said running 89 might have caused the problem because it would cool the fuel too much.

 

Service manager is full of BS........ Higher octane burns hotter!!!!! The higher theoctane, the higher the ignition point...... Ask for someone who actually knows something.........

 

Wow! Is there ANYBODY who works at your dealership who knows ANYTHING about internal combustion engines???

 

This is not correct. The higher the octane the slower it burns to prevent preignition. The reason you get more power from a higher octane fuel is that in higher compression engines (which is where the additional power is created) is that it does burn slower and is timed correctly so that preignition does not occur. You get the best performance from the lowest octane you can run without detonation. The moral of this story is that if you have an engine designed to run on 87 octane and choose to run VP C-16 you are throwing away $15/gallon fuel and no additional HP.

 

This is basically correct, however, not related to temperature, as higher octane does in fact burn hotter. It also has a higher ignition point. The purpose of octane boosters is to slow the spread of the flame front, thereby stopping the flame from bouncing off the opposing wall, and coming back as pre-ignition, or ping, or knock.

I did a complete study of this, back in my "answer man" days with a large gas utility company. Had much help from Chevron, and a few other gasoline companies. There is no benefit to running higher octane gasoline than is required by your engine (design parameters). If it ain't knocking, lower will suffice. Same energy, same product, the only difference being the octane enhancer. In fact, some premium blends actually have less energy, if the octane booster is ethanol.

 

I've had the same problem with my truck, i got about 181000 miles on it and the fix for me has been, replacement of the spark plugs, sometimes only on #2 and roll with it, and changing of the gas station, Chevron and Shell only. Unless i go out of town and i cant find a shell or something like that. It helped. Also runing 89 and sometimes 87. Also, u can run some fuel additive type cleaner from oreily, its made by chevron to clean up the valves. I didnt want to go to the dealer because they are idiots. Big big idiots. If it doesnt show nothing on their scan tool, then its fine. Parts changers, not mechanics. A friend of mine which is a mechanic on mercedes, told me that mercedes has the same problem with one of their v6 engine on #3. And its carbon build up from lower grade gas. He told me chevron and shell are the best because they add different additives that help the engine.

 

Okay but this truck as 27k of easy light duty miles on it not 181k and half of NJ runs this gas. If its carbon build up it sounds like a design flaw to me. I have had ZERO problems with my Ford and Toyota on this same gas.

 

I would take a look at the plugs.

If they look like new its possible to have a bad injector, if they are black and oily you may have mechanical issues and if they smell like fuel you may have spark issues.

FWIW OBD misfire monitors are not 100% accurate, if the #2 missfire is an ignition coil related code (P230x) then its probably a coil. If its a P030x then it could be another cylinder causing the issue and showing up as #2. If you can feel a misfire then a simple cylinder balance test by cutting injectors should show the problem cylinder.

I dont think it would be an MDS issue, thats cylinders 1-4-6-7 I believe.

I'm not that familiar with these but I have a ton of experience with OBD/EFI engines in general. My best advise would be find another dealer..