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Discussion Starter #21
At 158k miles you might be due for a new throttle body. They do have wear points and yours could have some of these. Bushings on the butterfly plate, motor and maybe a few others. Crank sensor as well as cam position sensors can cause issues without codes, been there done that.
Ended up ordering a new throttle body that is scheduled to show up tomorrow. Probably install it on Friday and see how things go. Probably look into injectors after that. Patiently waiting for the CC to come in still.
 

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Hey guys,
about the safety recalls. I got lucky and my local dealer had an extra cat in stock after calling all over town. I am experiencing the same problem as well but I'm getting around 14-17mpg. Stil after the new cat.
2012 avenger se 4cycl 91k
Things I've check:
Test evap canister, changed fuel strainer(89k), used seafoam twice in a months span,(. Cleaned throttle (which wasnt as dirty)
I do live in hot desert and notice car runs better when in 80-90s f°.

I just changed the spark plug back to oem Ngk today and will update on changes. Also will check fuel the injectors, those we
Any other suggestions will greatly appreciate thanks.
I included some live data pic. Thanks.
 

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NO CEL and when scanned NO DTC's? what is the coolant temp when running? are the T-stats installed? You're going into closed loop operation, so things must be good and fuel trims are not way out.
What kind of driving do you do? low speed "city" stop and go or mountains? Very short 5 mile or less drive times? All of these will give low MPG and nothing is wrong.
 

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No cell. Engine temp 194°f
Mostly city driving about 20-30miles/day.
Oem spark plugs great . Acceleration felt more responsive.
My mpg shouldn't be that bad.
Also my rpm rev up/down every 15sec. Or so. Only when ac on. From normal idling (7~800rpm) to 1100~rpm.
Included were live data around 34mpg.
 

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Discussion Starter #25 (Edited)
No cell. Engine temp 194°f
Mostly city driving about 20-30miles/day.
Oem spark plugs great . Acceleration felt more responsive.
My mpg shouldn't be that bad.
Also my rpm rev up/down every 15sec. Or so. Only when ac on. From normal idling (7~800rpm) to 1100~rpm.
Included were live data around 34mpg.
Curious if you had found the issue? I'm STILL having the same problem with my car and you're explaining exactly what my car is doing when you mention that it will "rev up/down every 15 seconds with A/C or heater on." With the weather heating up I've been using my A/C the last two days and my average MPG has gone from 20.9 to 20.2 in those two days. There's no way that this is normal, even with driving around for a couple miles each day.

I know it's been quite some time since I've posted on here, but since my last post I put a new set of NGK platinum plugs in, new injectors and new coil packs. Any suggestions would be greatly appreciated. Also, I had the recalled CC taken care of as well.
 

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Just checking in to say that I've had the exact same issue with the 2.4 for years- suddenly terrible mpg, rough idle with the same bounce from 7-800 to around 1100 rpm at idle. We were never able to get to the bottom of it, and I've done many of the fixes mentioned here too! I'm curious to see if either of you come to a realization that may help me out as well!
 

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This is SPECULATION :
From what keeps getting posted of wavering RPM, There will always be some slight RPM variance and particularly with A/C running. But should not be more than 100 rpm.
A couple of thoughts as to why from THEORY of engine management...
A slight engine vacuum leak that the computer is managing to compensate, at reduced fuel economy and RPM variance. Gould come from PCV valve or tubing. A MAP sensor thats "gunked up" at sensing port or dying. OR a slight intake manifold to cylinder head gasket leak(fairly common on the 2.4). NO WAY to pinpoint any of these over the Forum to specific members concerns. It is a matter of following and doing proper diagnostic steps and component inspection of each possibility presented, and yet these may not be the actual cause to each members symptoms described.

GOOD LUCK TO ALL involved with this type symptom reading along here!
 

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Discussion Starter #28
This is SPECULATION :
From what keeps getting posted of wavering RPM, There will always be some slight RPM variance and particularly with A/C running. But should not be more than 100 rpm.
A couple of thoughts as to why from THEORY of engine management...
A slight engine vacuum leak that the computer is managing to compensate, at reduced fuel economy and RPM variance. Gould come from PCV valve or tubing. A MAP sensor thats "gunked up" at sensing port or dying. OR a slight intake manifold to cylinder head gasket leak(fairly common on the 2.4). NO WAY to pinpoint any of these over the Forum to specific members concerns. It is a matter of following and doing proper diagnostic steps and component inspection of each possibility presented, and yet these may not be the actual cause to each members symptoms described.

GOOD LUCK TO ALL involved with this type symptom reading along here!
Way back when I had the fuel system cleaned, a mechanic suggested a smoke test when I was telling him my problems and symptoms. Is this something that would detect the first two things you theorize?
 

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Only if done while condition is present. When engine is cold and not showing the symptom, it would not detect it. Most "smoke tests" done are for EVAP system leaks that do not go into "on the motor" parts.
Was going to wait for further THEORY(speculation) posting on next steps involving Ignition/timing aspects to posted symptoms...ONE area at a time.
 

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Discussion Starter #30
Alright... I've thought a lot about 5rebel9's speculation of an intake manifold gasket leak. As I was thinking about that, it was making a lot of sense. So, I started doing some research and pricing. While researching I came across a somewhat common problem in the intake manifold runner control valve getting stuck. My plan is to start with inspecting the IMRC valve shaft to ensure proper function, then replace the IMRC, and then if THAT doesn't solve the issue I'm going to change out the intake manifold completely (with a new suggested gasket, of course). I'll report back periodically. I think 5rebel9 may have nudged me in the right direction though, so thank you! 🤞
 

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Discussion Starter #31
Two months since my last post (and how times have changed since). To catch up on what I did;

~Removed the intake manifold to inspect the IMRC only to discover that my car didn't have one.
~Installed a new Intake Manifold Gasket.
~Re-installed the Intake Manifold.

With that mentioned, there has been ZERO change and the issue remains. I'm still leaning towards a fuel/air mixture issue but I'm at a complete loss and feeling very defeated. One thing worth mentioning is I did a MPG test a couple days after installing the new Intake Manifold Gasket. I reset the MPG gauge while already going 80mph and monitored it for approximately 150mi at that sustained speed. Before I exited the freeway the gauge read "24.6mpg." To reiterate, the 80mph was sustained and without stops. Clearly there is something wrong and STILL no CEL.

I'm getting to the point of either spending money on a diagnosis, or trading the damn thing in for something new. If anyone has any more suggestions I would be MUCH obliged! Thanks in advance.
 

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Two months since my last post (and how times have changed since). To catch up on what I did;

~Removed the intake manifold to inspect the IMRC only to discover that my car didn't have one.
~Installed a new Intake Manifold Gasket.
~Re-installed the Intake Manifold.

With that mentioned, there has been ZERO change and the issue remains. I'm still leaning towards a fuel/air mixture issue but I'm at a complete loss and feeling very defeated. One thing worth mentioning is I did a MPG test a couple days after installing the new Intake Manifold Gasket. I reset the MPG gauge while already going 80mph and monitored it for approximately 150mi at that sustained speed. Before I exited the freeway the gauge read "24.6mpg." To reiterate, the 80mph was sustained and without stops. Clearly there is something wrong and STILL no CEL.

I'm getting to the point of either spending money on a diagnosis, or trading the damn thing in for something new. If anyone has any more suggestions I would be MUCH obliged! Thanks in advance.
Well your MPG has gone up from 17 to 25 so there is a significant improvement. Your car has fairly high mileage so things do wear. Have you replaced the injectors, timing belt, MAP sensor, or fuel pump?
 

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80mph is not the sweet spot for these cars.
You might be able to get 30-32mpg if you kept it under 70mph
 

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Discussion Starter #34
Well your MPG has gone up from 17 to 25 so there is a significant improvement. Your car has fairly high mileage so things do wear. Have you replaced the injectors, timing belt, MAP sensor, or fuel pump?
For clarification, 17 mpg was what I was getting when I would leave the gauge alone for months. 25 mpg was what I got when I reset the gauge while already up to 80mph and sustained that speed for150 mi. Since then, I have not reset it and it’s back down to 19 and still falling. I have replaced the injectors, map sensor and the serpentine belt (not timing) but haven't messed with the fuel pump yet. I ordered a scan tool last night and it should be here later this week, so I’ll see if anything pops up on it, but still no CEL.
 

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Just so you know... The mileage figure in the EVIC is an approximation by computer algorithm AND is Cumulative of ALL driving/idling done between resetting the gauge. It is therefore NOT a precise and accurate means of determining actual fuel mileage. Your most accurate way is to start with a full tank of gas and drive the car till next fill up and then divide miles driven by gallons used.
 

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Discussion Starter #36
Just so you know... The mileage figure in the EVIC is an approximation by computer algorithm AND is Cumulative of ALL driving/idling done between resetting the gauge. It is therefore NOT a precise and accurate means of determining actual fuel mileage. Your most accurate way is to start with a full tank of gas and drive the car till next fill up and then divide miles driven by gallons used.
Thanks. You make great points that I was already aware of. But tell me this:

Should I be getting a MAXIMUM HIGHWAY mpg of 25 and MIXED (highway and city) mpg of 17?
 

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Depending on your driving conditions, IF you look back to EARLY posts here of fuel mileage reports then YES that is about the average particularly for yours with now older and high mileage on it. A 4cyl. has to work a bit harder to move the mass of the sedan avenger compared to the V6 models and how one uses the "go pedal" comes into play, as was posted in reply #33
I'm sorry if you feel differently about fuel economy wishes.
 

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Discussion Starter #38
Depending on your driving conditions, IF you look back to EARLY posts here of fuel mileage reports then YES that is about the average particularly for yours with now older and high mileage on it. A 4cyl. has to work a bit harder to move the mass of the sedan avenger compared to the V6 models and how one uses the "go pedal" comes into play, as was posted in reply #33
I'm sorry if you feel differently about fuel economy wishes.
I’m aware of earlier posts, but thanks for the reference. I’m also fully aware that the more the “go pedal” (as you call it) is engaged, MPG will fall.

See attached photo from fueleconomy.gov that seems to contradict your opinion.

19051
 

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YUP ESTIMATES on NEW CAR RATINGS...YOUR mileage will VARY. For a HIGH MILEAGE vehicle, YOUR'S is NOT that badly off for new ratings....SORRY to hurt your feelings.
 

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YUP ESTIMATES on NEW CAR RATINGS...YOUR mileage will VARY. For a HIGH MILEAGE vehicle, YOUR'S is NOT that badly off for new ratings....SORRY to hurt your feelings.
My feelings are fine. Yours on the other hand may not be, judging by your use of caps. Still contradicts your opinion that the 4 cylinder has to work harder than the V6.

You’ve come across with a bad attitude in this thread before and I’ve read other threads that you did the same thing and users called you out on it. I think it’s best if you excuse yourself from this thread. You’ve given your suggestions, which I was greatly appreciative of and even gave you credit for help, and you respond with smart ass remarks like “go pedal.” Have a GREAT day!
 
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