Quote:Originally Posted by FunkapotimusI just recently purchased a 2007 Dodge Charger (yay) and whomever was the pervious owner on it didn't drive it much but he did do a mod under the hood. it's a simple 3.5L v6 but the previous owner added an AEM Brute Force air intake. However a friend of mind noticed that when my Car is idling the idle sometimes drops low for a moment then picks back up again, and it'll do it once every 2 minutes or so, sometimes even at a stop light I'll notice it. I was wondering if the odd idle was cause of the intake not matching up properly with the engine or if it's something else. I was thinking if it is the Air intake maybe I need to change the fuel injectors to help match it up ?
Also the previous owner added on a after market exhaust from a single tip to a split pipe

Quote:Originally Posted by GertFrobeThe modified exhaust is fine, the engine doesn’t care about it in terms of idling. If anything it might be breathing a little easier with that non-stock exhaust if not as restrictive as stock setup.

The aftermarket air intake is also theoretically an acceptable mod for that engine, and it does not require, nor would it benefit from, different fuel injectors being installed. The stock injectors can spray more gas than the engine could ever burn, even when it’s ingesting the absolute maximum amount of air that it possibly can at WOT.

Different injectors might be necessary if you had forced induction on the engine (turbo, super charger, nitrous) to feed it more air than normal atmospheric pressure can normally force into the combustion chambers, but the stock ones are fine as long as the engine remains naturally aspirated.

That does not mean the aftermarket air intake is not the culprit here though. In fact, I suspect that it is causing the erratic idle, even if inadvertently. It’s the first thing I would check if it were mine anyway. You should start your troubleshooting with it and it’s components either way, attempting to rule it out as the cause so you can move on and find what is causing the idle issues.

First, take the whole thing off the engine and completely disassemble it for inspection. It should only have a couple major pieces (intake tube, air box, and filter) and a few smaller ones (filter, clamps, elbow sleeves, breather hose), so a complete disassembly isn’t that difficult to do, but it is absolutely required to be able to rule it out as your cause (or find the proof that it is guilty of something).

Once apart, carefully inspect every joint, junction, and connection point on the device where it supposed have an air tight seal with some other part or piece. You are looking for signs that it is no longer sealing at one of these spots and thereby allowing the engine to suck in unfiltered air. Small dust trails of very fine dust will be a dead giveaway that an air leak has formed somewhere, and they are more common than anyone wants to admit on the aftermarket air intake systems like this.

Pay very close attention to the air filter element itself, especially where the element and wire structure are connected together. I have seen those types of filters develop leaks there from inadequate or too much epoxy being used during manufacturing assembly. Again, look for faint dusting on the surfaces adjacent to the join-surfaces to identify potential leak spots.

Also inspect the areas on the intake hose where the hose clamps normally reside. After a lot of miles and time, that rubber hose will begin to deteriorate and break down to the point of becoming brittle and prone to leaking under the stress of the (usually overtightened) hose clamps.

If you go over the intake system and cannot find evidence of an air leak, time to focus on the intake plenum that the air tube was attached to. It has several hoses and pipes that connect to the back of it, under the windshield cowl, and they are all supposed to be air tight too. But they will develop leaks as their hoses age and start to harden up. The EGR pipe connection point is especially bad about leaking if it has ever been disconnected and reconnected (like for a spark plug replacement).

The gasket between that intake plenum itself and the engine block can develop a leak as well, so that would be my next point of inspection if none of the rest panned out.

By now you might notice that are getting elbow deep into the engine, and as such you should consider changing things out that will be easily accessed during all this, which is likely required anyway if normal maintenance schedule is being followed.

New spark plugs, new PCV valve, serpentine belt, idler pulley, belt tensioner, a cleaned out intake plenum, etc...

Depending on many miles the engine has and how well the previous owner took care of it (or didn’t, hard to know without finding out for yourself), those things and more are due for replacing/cleaning and should not be ignored lest erratic idling becomes the least of your problems.

Don’t forget the timing belt, its tensioner, and the water pump either. Those are supposed to be changed every 100K miles, as is the engine coolant. Granted none of those are likely to be causing your idle problems, but if any of those are left too long in service, you could lose the engine for good with little or no warning.

But I digest...

How many miles are on the engine? If > 100K, you have a lot of maintenance services to consider performing while chasing this idle issue. My advice would be to buy a 2005-2010 Dodge LX Chilton’s Manual from Amazon or a local auto parts store and start making a list of what needs to be done and what can wait.

That manual will have some generic steps you can try to calm an erratic idle, but don’t put too much hope in the troubleshooting section of those manuals. Their one-size fits all approach to covering as many applications as possible doesn’t lend itself to being very useful when out to the test on the average joe’s broken vehicle.

One last tip: go to [MyCarFax]DOT[com] and create a (free) account there, providing this Charger’s VIN as part of the account sign up. That will allow you to see any of the vehicle’s service history that has been reported to the CarFax company.

You may find no entries at all, in which case you’re no worst off than you were before. But you could get lucky and find the previous owner took the car to places that reported their work and you’ll have a good idea of how well the car was maintained as well as if any severe problems or damage was in its past (and may need to be dealt with again).

Pretty good for free!

Gert

Originally Posted by GertFrobe
So while I’m thinking about it, I meant to ask before if you are running the air conditioner or defroster when this behavior is heard. If you have either of those on while listening to it idling up and down, turn them off and see if that stops the erratic behavior.

The engine will idle up a little when the air conditioner compressor kicks on, and it will idle back down when the compressor kicks off. So if the compressor is cycling on and off more than it usually would, you could perceive that as a problem with it idling when it’s actually behaving the way it is supposed to (but the reason for the fast cycling of the compressor would still need to found eventually).

Quote:Originally Posted by Funkapotimus Yeh I made sure everything was turned off completely in the car while the odd idling happens, no heat, no a/c, not even the fan running, just the engine.