Engine Idles rough

[deknight]

I've got a 2.4L with around 46k on it, but this question might apply to everyone else as well. I have started to notice that the engine idles kind of rough when the engine is warm. When its cold, it revs around 1000rpms and its fine. I also noticed that my gas mileage was about 3 mpg lower then usual. So I changed out my spark plugs with Champion Platinums, which were the only thing the store had. I was surprised to see that the dealer used regular champions as well. (Who knows how much they marked those up when I had the service done 13000k miles ago).
Anyway, my gas mileage is back up to where it should be, but the engine idles rougher then it used to. Actually to use the term rough is an over statement, the engine flutters or feels like it misses a beat every 10 seconds.
So my question is, does this sound like the spark plugs? I have read that champion plugs are trash but could new plugs make it worse? All the vacuum lines are fine, and I just cleaned my k&n air filter. Could it be something else?

 

[Marlon_JB2]

Champion regular plugs are definitely trash, I don't know about their platinum plugs.

Maybe they're not gapped properly?

 

[deknight]

I checked the gaps and they were all correct. I am going to try different plugs, maybe autolites and see what happens.

 

[Dave]

Does the 2.5liter have the coil packs on top of the plugs?? You'd think it would throw a code though. Make sure one is not loose.

Dave

 

[thecause17]

The 2.4 doesn't have the coil packs, it has plug wires. Have you done any other tune up procedures other than the plugs? How about plug wires? If not, I suggest you do that, replace the fuel filter and run some injector cleaner through it and see what you get out of it. If it's stuff you haven't done, you should do it anyway, and they're the cheapest way to start when trying to solve the problem.

 

[MoladoGuy]

Champion Plugs (blarg)

I put them in recently and ran it for about 2 months. I gapped them correctly and ensured that no debris fell into the plug areas. Weird off the line starts and the idle was different. I put in Bosch Platinum plugs and everything is back to normal.

 

[deknight]

I have a feeling now that its not the spark plugs, although I am going to change those anyway now that i bought autolites. I think I may have a vacuum leak somewhere. Every time I rev the engine I can hear a loud hiss of air for about a second then it stops. (I can't hear it unless I am under the hood and I open the throttle by hand). And it seems to be coming from the throttle body area. So I took everything apart again, there isn't much on the 2.4, just the air cleaner box then the throttle body and a few electrical plugs (one goes to the mass air flow sensor and two go to the throttle). Checked everything, put it all back together and it still does it. So i don't know at this point, I might try checking the pcv valve when I get a chance this weekend.

 

[MoladoGuy]

I have a feeling now that its not the spark plugs, although I am going to change those anyway now that i bought autolites. I think I may have a vacuum leak somewhere. Every time I rev the engine I can hear a loud hiss of air for about a second then it stops. (I can't hear it unless I am under the hood and I open the throttle by hand). And it seems to be coming from the throttle body area. So I took everything apart again, there isn't much on the 2.4, just the air cleaner box then the throttle body and a few electrical plugs (one goes to the mass air flow sensor and two go to the throttle). Checked everything, put it all back together and it still does it. So i don't know at this point, I might try checking the pcv valve when I get a chance this weekend.

I would like to confirm if this is really an issue. Only because I can manually rev the engine inside the engine bay using the TB by hand and hear a quick hisss...To me that hiss sounds like air being sucked in rather than a leak somewhere. I also cleaned the TB after this incident and the hiss is still there.

Can someone confirm that their 3.7L or 2.4 makes the Hiss sound when manually revving the engine???

 

[deknight]

What you are describing is exactly what I was trying (in so many words) to say. It does sound like a hiss and only lasts for like a second then goes away. I don't remember it ever doing it before, so I don't think that its normal.....

 

[tjkj2002]

What you are describing is exactly what I was trying (in so many words) to say. It does sound like a hiss and only lasts for like a second then goes away. I don't remember it ever doing it before, so I don't think that its normal.....

Mine does it,even when I had the stock airbox,even more so with the AFE induction.Just the air getting sucked into the engine.

 

[Marlon_JB2]

What you are describing is exactly what I was trying (in so many words) to say. It does sound like a hiss and only lasts for like a second then goes away. I don't remember it ever doing it before, so I don't think that its normal.....

That sound is nothing but air being sucked into the engine. Entirely normal.

 

[deknight]

Okay thanks everyone. I just checked my pcv valve and its fine, I will change out the plugs and see if that fixes it.

 

[tjkj2002]

Okay thanks everyone. I just checked my pcv valve and its fine, I will change out the plugs and see if that fixes it.

Don't forget the plug wires! It's pointless to replace the plugs and not do the wires to(since you have the 2.4).

 

[Mick]

My vote would be for the plugs too. New Autolite platinums did wonders for the rough idle on my 3.7.

Don't forget the plug wires! It's pointless to replace the plugs and not do the wires to(since you have the 2.4).

A side question. What is the life of the coil packs on the 3.7s? It's basically giving each plug it's own transformer. Delivering the high voltage directly to the plug, eliminating the wire. So my guess would be that the pack will last as long as the transformer. But how long is that?

 

[tjkj2002]

My vote would be for the plugs too. New Autolite platinums did wonders for the rough idle on my 3.7.


A side question. What is the life of the coil packs on the 3.7s? It's basically giving each plug it's own transformer. Delivering the high voltage directly to the plug, eliminating the wire. So my guess would be that the pack will last as long as the transformer. But how long is that?

They will last,since the 3.7's do not have plug wires there is one less thing that needs to be replaced.When a coil pack on a 3.7 goes bad it will turn on the check engine light alsh by the way since the coil pack does not need to push high voltage through a plug wire it will last longer,less wear on it.

 

[deknight]

Well... I think I can finally put this one behind me! I changed out the sparkplugs and put the Autolites in and the thing runs like new. How in the world can one brand of spark plug make such a difference? Same heat range, same gap. It's beyond me. Let this be a lesson for everyone, STAY AWAY FROM CHAMPION! (At least with the Liberty). And be careful because the dealer put regular champions in mine the last time I had them changed and ever since it has been skiping a beat when it would idle for the last year. I never even thought it would be the spark plugs. Maybe every dealer is different or maybe they just use what's cheapest.

 

[Marlon_JB2]

Well, a long long long time ago, Chryslers used to work very well with Champions.

They don't anymore and I guess the dealerships keep using them...

 

[Dave]

Well... I think I can finally put this one behind me! I changed out the sparkplugs and put the Autolites in and the thing runs like new. How in the world can one brand of spark plug make such a difference? Same heat range, same gap. It's beyond me. Let this be a lesson for everyone, STAY AWAY FROM CHAMPION! (At least with the Liberty). And be careful because the dealer put regular champions in mine the last time I had them changed and ever since it has been skiping a beat when it would idle for the last year. I never even thought it would be the spark plugs. Maybe every dealer is different or maybe they just use what's cheapest.

Glad you got it fixed and it was just the plugs. Did you use the regular Autolites or the platinum. Just curious.

Dave

 

[thecause17]

It'd still be a good idea to change the wires if you haven't in the past...

 

[MoladoGuy]

Good job!