I have a 2005 Sebring Sedan Auto with the 2.4L engine, it currently has 53k on the clock and over the past three years it has had a slight engine miss. The last year it has gotten worse. Seems to do worse when its cold or rainy (might be my imagination on the rainy days).

It will shake and the lights will dim etc. It will do it driving or sitting still, no specific MPH or no specific trigger. It just does it sometimes for a couple of seconds, sometimes for a few seconds... sometimes for a good bit. Its gotten more and more regular that it will do it.

It throws no engine lights and I have had a shop run diagnostics on it with zero results or ideas... the only thing they told me to do was let the dealership look at it to see if it has the latest firmware installed....

I have tried searching and perhaps I am searching the wrong terms, any help would be greatly appreciated in terms of trying to figure out and fix the issue.

Being that it has 50k miles its going in for regular maint. soon which will include fuel filter, coolant, trans fluid, oil and filter etc. The fuel filter couldbe a a part of it but as I said it only does it now and again not all the time etc.

 

Usually, when electical items fail they will throw a code, which may or may not cause the check engine light to come on, depending on what it is. Problems with the fuel system are sometimes not accompanied by a code because there is no sensor to detect things like a sticky fuel injector or plugged filter.
A random miss should throw a code no matter what it's caused by, but unless it's somewhat persistent, it may get erased with time.
A guess as to what your problems might be would include a clogged injector or a failing ignition wire or spark plug.
I don't know what kind of equipment your "shop" hitched up to the car but a better diagnostic, especially when the miss is present, might turn up a better answer.

 

This sounds a bit hokey, but disconnect your battery (the negative post up in the engine bay), disconnect your air intake tube, use a toothbrush and a throttle body cleaner to make the inside of the throttle body and butterfly (front and back) shine like new. You'll see two small passages, one on the outside of the butterfly, one on the inside(these are the passages for the Idle Air Control), make sure to get some cleaner inside them. Reconnect the battery and...

Next, buy a GOOD fuel system cleaner, one that costs $10+ a bottle, there's a reason some only cost $2 a bottle; their effectiveness is what you pay for. Most recommend that you run the tank down to at least a quarter, then add the cleaner before filling the tank.

I'll admit straight off that I'm not a professional mechanic, but I work on, and am asked about, a lot of cars and in my experience, the two most common cause of an undetectable problem like this are a dirty throttle body and sludged up fuel system. The reason for disconnecting the battery is to allow the engine controls to relearn the now properly flowing induction.

Also, fuel and air filter, but you already said you'll have that covered

 

Thanks for the input! Actually yesterday evening right before I got home the check engine light came on. My code reader wont read them on the car for some reason (SCT X-Cal 3) but... I am going to run by somewhere and get them read to see what they say... wish me luck... and good advice on all the above. I also want to change the plugs and inspect them while I am messing around in there.... any input on how hard/easy this is on the 2.4L? and any tips/tricks on which plugs to get (was gonna just go OEM but wanted to make sure on specifics in case the guy sat the auto place dont know)

 

"Just give me the OEM" can sometimes lead to bad results at the parts store :\

I swear by Bosch, but there are many who swear at them as well, NGK is another quality brand. No matter what brand you go for, Platinum would be what your car came with and Iridium would be an upgrade. If I'm remembering right, the plugs should be front and center on the engine and you'll need an 8mm to take off the coils and a 5/8 spark plug wrench to do the job

 

Don't gap platinum plugs. They come gapped and using a tool to check the gap can scratch off the platinum coating.

When loosening the plug, just crack it loose, then turn it back in. Then loosen it a little more and turn it back in again. Continue doing that until it's out. What can happen is you might get a little bit of carbon on the end of the threads. You want to break that off, not drag it through the threads on the way out. Aluminum heads are soft and easily buggered up.
Use some anti-seize on the threads when installing the new plugs. Start them in their holes by turning them with a piece of tubing or rubber hose slipped over the end so as to not cross thread them.

 

Just because it would seem to be a good idea for a forum visited by amateur mechs of various abilities and experience, is there anyplace in the forums where general "Department of the Painfully Obvious to Some" things like this are "Sticky" for easy reference?

 

FYI, TSB 08-008-04 was issued for the 2.4 engine recommending that ONLY Champion Copper Plus plugs be used. I popped in a set 3 weeks ago and my 2004 SEBRING LX runs better than ever! Buy Champion Copper Plus Automotive Spark Plug 443 at Advance Auto Parts

 

I think people who want to post up "How-to's" with pictures are best able to do so here by creating a photo album with captions explaining the various steps.

You're right, there should be a better way and place to do so.

There are lots of things that come up time and again that get lost in a thread.