2012 hemi decreased fuel economy

[Chiefs88420]

My 2012 1500 hemi is not getting very low fuel economy around 400km to a tank. Nothing has changed except replace fuel pump . Tires are new and balanced . Alignment is fine. Newer spark plugs. I do notice alot of shaking when going over 100km on highway but I figured this was the dodge death wobble. Maybe the fuel saver mode when it drops to 4 cylinders is not working properly?

 

[Jeepwalker]

Have you scanned for any codes (like a missing engine)? An engine that was misfiring would cause poor fuel economy and possibly some shaking.

 

[crash68]

I do notice alot of shaking when going over 100km on highway but I figured this was the dodge death wobble.

The "death wobble" is prevalent on solid front axle vehicles, your 1500 has an independent front suspension.
When you say 400KM(250 miles) on a tank of fuel, how much gasoline are you talking about? Have you tracked how much fuel used vs mileage for multiple full ups?

 

[Chiefs88420]

About 80 litres. I have tracked this on multiple trips and gas from differnt stations. I used to get close to 600km to a tank and now it is in and around 400km. I know when in the eco mode (drops to 4 cylinders it feels like it shudders.) I scanned for codes but nothing came up.

 

[Wild one]

About 80 litres. I have tracked this on multiple trips and gas from differnt stations. I used to get close to 600km to a tank and now it is in and around 400km. I know when in the eco mode (drops to 4 cylinders it feels like it shudders.) I scanned for codes but nothing came up.

Check for a dragging caliper or parking brake. Take it for a decent drive,and then see if one brake seems hotter then the rest.

 

[Jeepwalker]

The "death wobble" is prevalent on solid front axle vehicles, your 1500 has an independent front suspension.

That's true.

You could have a couple things going on. Like was suggested, check that the wheels rotate freely, Run your hands over the tires as you have them jacked up off the ground. You might have something going on there which could be a broken chord and also increase rolling resistence.

Any codes? Could be one of your new spark plugs has failed. There are 2 per cyl ..did you replace both? Although rare, I've had that happen more than once after putting in new plugs ..where one crapped out or the porcelean broke or I mistakenly cracked it. That might cause shaking and reduced fuel mileage. So could a bad coil. But one would expect a Service Engine Soon light on either of those. A dirty MAF that reduced the reading to the low range of normal (but not quite totally out of spec) ...or a lot of fuel deposits ..gum build-up around and on the throttle plate would (could) do it. Get some MAF and Throttle Body cleaner and clean those areas appropriately. Those are common easy-to-ignore or forget about maintenance items.

Hope those suggestions help. Good luck

 

[indept]

Since it started when you replaced the pump, maybe the fuel level part of the pump is off. Make sure the amount of gas to fill is correct versus the guage. So the standard tank sizes are 26 gal (98.5 L) and 32 gal (121 L) so if you're tank is the 98.5l and your gauge reads 1/4 full you should take approximately 75 L.

 

[Chiefs88420]

Thank you all I shall try these things and get back to you

 

[Chiefs88420]

Hey everyone.

I cleaned the throttle body, was not to bad
Looked for codes no codes
Emergency brake not stuck on.
Spark plugs seem to be fine as they were changed 40000km ago..
Fuel pressure vaccum on the scanner was fine.

From what I have read on Google. This is a common issue after changing fuel pump.

I am currently waiting for my gas light to come on and going to drive it until it dies to see if there is more fuel then there should be.

Other day I drove 120km and used a half tank.


How can I tell if I have a bad fuel pressure sensor? Would I not have codes if something was wrong with my mixture ir fuel system?

Thanks

 

[Chiefs88420]

Bump

 

[Chiefs88420]

Fuel pump and guage seem to be okay.

I tested my o2 sensor with a code reader. And seem to be okay.what numbers should I be seeing?

 

[Russ007]

Ethanol blends will decrease mileage. E15 is more common

 

[Hagar1]

My 2012 1500 hemi is not getting very low fuel economy around 400km to a tank. Nothing has changed except replace fuel pump . Tires are new and balanced . Alignment is fine. Newer spark plugs. I do notice alot of shaking when going over 100km on highway but I figured this was the dodge death wobble. Maybe the fuel saver mode when it drops to 4 cylinders is not working properly?

I am having the exact same problem. My spark plugs have less than 2000km on them. This problem started last spring. Along with the drop in fuel economy, I have a cold driveability problem as well.
No codes ....
I have noticed random "misfires" but only a one per drive cycle and always on a different cylinder. That one is a puzzle. Sometimes several drive cycles and no misfires. Never turn the light on.

 

[Hagar1]

Ethanol blends will decrease mileage. E15 is more common

I checked the alcohol content on the fuel that I use and it tested at 3% which is actually quite low.

 

[Wild one]

I am having the exact same problem. My spark plugs have less than 2000km on them. This problem started last spring. Along with the drop in fuel economy, I have a cold driveability problem as well.
No codes ....
I have noticed random "misfires" but only a one per drive cycle and always on a different cylinder. That one is a puzzle. Sometimes several drive cycles and no misfires. Never turn the light on.

Where did you get the new plugs from? There's lots of Chinese knock-off plugs floating around these days

 

[Hagar1]

Where did you get the new plugs from? There's lots of Chinese knock-off plugs floating around these days

Auto Value store. NGK and they are the ones specified for that application. Never thought to ask if they were Chinese knockoffs though. This problem started long before the spark plug change. I put new lifters in it about the same time as the spark plugs. The cam was good, like new. The fuel economy problem literally happened overnight back in the spring.
The "misfire" is of no significance, in my opinion, because it happens so infrequently. Not enough to be stored long term, nothing in "freeze frame" or any other place.
It is truly a puzzle.

 

[Jeepwalker]

You're using Regular fuel, right? Not E85? Try a tank of premium. If your truck is using THAT much fuel you'd have to see it in the plugs. For sure the tailpipe.

I would go back and look at your spark plugs for plug-end condition. The color and condition of the plugs tells a meaningful story. If you have a poorly-firing cylinder you should see it on the plugs. Lay them out on a table in order how they go in the truck.

After you take one plug out per cylinder, do a compression test. Watch a couple videos, they explain how. Autozone & OReilly's rents them out at no charge. A leak-down test would be good too. Then remove the rest of the plugs. Again compare notes.

While you're at it, ohm-out each coil, and inspect the plug-end-side for any cracks or electrical burning/traces, etc.

What is the exact fuel pressure? Test that and get a reading. There's a fuel pressure regulator back below the brake booster which often flakes out. Watch a video on that.

Couple other things to note are:
1) What's the MAF voltage? A poor mass air flow senor, even while it CAN technically still be 'good' ...I've seen them come in at the extreme low end of the voltage and a vehicle run like crap (rich), but not throw a MAF code. To test, unplug it, start/run/drive, and the vehicle should run in closed loop but run smoother. They can be cleaned with MAF cleaner (ususally slight improvement), but being a 2012, I'd replace with a new MOPAR (not import) one. Unless it's a Bosch.

2) Temp sensor? They can drift and the vehicle might "Think" it's a different temp than it is. Ohm it out engine-cold, and engine warm. Compare the readings to a Ram ohm/temp table.

3) Air restrictions? Make sure there isn't a mouse nest in your truck's air cleaner box, or something restricting air flow. I've seen it..

4) Vacuum? If you rent a compression tester, rent a vacuum gauge. You could have a vacuum leak. Watch some vacuum gauge videos. Vacuum tells you another story of an engine. ..

 

[Jeepwalker]

On your tires, go find a shop which can do a "Good" Road Force balance job. You probably got a terrible balance job, or out-of-round tire.

95% of tire techs out there will find a new and innovative way to shortcut or screw up an important step in the tire changing/balancing process. That's been my observation. You gotta stand right there and watch them like a hawk for the ENTIRE job, and not be afraid to bark out corrective actions if/when needed. Preferably you have a nice conversation with them as they're doing it. NEVER just drop off your truck and come back later!! Last year I had a tire tech who was going to install a tire on a rim AFTER he'd cleaned the white walls off ...there was at least a quarter cup of water in the tire. I had turned to answer an email and he was about to put the tire on with the water inside the tire!! I put an emergency stop to it and made sure we removed the water and completely dried out the inside of the tire. That's the kind of thing I'm talking about. I could tell other stories. Point is, a guy can't turn his back on a tire tech for even a minute! Unless you know your tire tech personally and trust for sure he is a stickler for details. Even then I wouldn't leave the process unchaperoned.

Go to a shop which has a Road Force balancer (the best), by Hunter, which many/most shops have (but many don't use for normal tire balance jobs). Pay the extra to have it done. It will uncover any weaknesses, out-of-round tires, bent rim, wrong weights, hard-spot in the rubber ....or whatever. Once tires wear-in to bad weights or out-of-roundness, they're kind of set after a while. So do it sooner than later. If they StiLL don't find anything. have them put a dial indicator on the rims (on the vehicle) and check for wheel run-out. I bought a brand new OReilly's hub/bearing 2 yrs ago and it was pre-warped out of the box. And this wasn't the economy model either. I put the dial indicator on it before installing and it was .005" deflection at the outer edge of the hubface. SO... even perfectly balanced tires would be wobbling if I had installed it. (and give a shimmy). I took it back, they probably re-sold it, or it made it's way on ebay to some unsuspecting owner (maybe you??!). LOL Spend the $$ on Mopar stuff.

Of course have them check for worn suspension parts/components incl bad shocks.

Let us know what you find.

 

[Hagar1]

On your tires, go find a shop which can do a "Good" Road Force balance job. You probably got a terrible balance job, or out-of-round tire.

95% of tire techs out there will find a new and innovative way to shortcut or screw up an important step in the tire changing/balancing process. That's been my observation. You gotta stand right there and watch them like a hawk for the ENTIRE job, and not be afraid to bark out corrective actions if/when needed. Preferably you have a nice conversation with them as they're doing it. NEVER just drop off your truck and come back later!! Last year I had a tire tech who was going to install a tire on a rim AFTER he'd cleaned the white walls off ...there was at least a quarter cup of water in the tire. I had turned to answer an email and he was about to put the tire on with the water inside the tire!! I put an emergency stop to it and made sure we removed the water and completely dried out the inside of the tire. That's the kind of thing I'm talking about. I could tell other stories. Point is, a guy can't turn his back on a tire tech for even a minute! Unless you know your tire tech personally and trust for sure he is a stickler for details. Even then I wouldn't leave the process unchaperoned.

Go to a shop which has a Road Force balancer (the best), by Hunter, which many/most shops have (but many don't use for normal tire balance jobs). Pay the extra to have it done. It will uncover any weaknesses, out-of-round tires, bent rim, wrong weights, hard-spot in the rubber ....or whatever. Once tires wear-in to bad weights or out-of-roundness, they're kind of set after a while. So do it sooner than later. If they StiLL don't find anything. have them put a dial indicator on the rims (on the vehicle) and check for wheel run-out. I bought a brand new OReilly's hub/bearing 2 yrs ago and it was pre-warped out of the box. And this wasn't the economy model either. I put the dial indicator on it before installing and it was .005" deflection at the outer edge of the hubface. SO... even perfectly balanced tires would be wobbling if I had installed it. (and give a shimmy). I took it back, they probably re-sold it, or it made it's way on ebay to some unsuspecting owner (maybe you??!). LOL Spend the $$ on Mopar stuff.

Of course have them check for worn suspension parts/components incl bad shocks.

Let us know what you find.

Thank you forcthe detailed explanations. I have all the tools that I might need. I dare say that I'm better equipped than some commercial shops.
I have already checked the plugs and there are no issues with them. The air/fuel mixture is burning well. The cats are doing their job otherwise I'd likely see an o2 sensor code and a mil. Had the heads off about a month ago and that engine is healthy. No significant build up of carbon. Once it warms up the drivability thing gets a lot better but fuel economy is still down about 30 percent.
I have checked coolant, intake air and ambient when engine has sat over night. They are all within a degree.
The 5.7 like most chrysler products, utilizes a "speed/density" system and does not use a mass air flow sensor.

 

[Hagar1]

On your tires, go find a shop which can do a "Good" Road Force balance job. You probably got a terrible balance job, or out-of-round tire.

95% of tire techs out there will find a new and innovative way to shortcut or screw up an important step in the tire changing/balancing process. That's been my observation. You gotta stand right there and watch them like a hawk for the ENTIRE job, and not be afraid to bark out corrective actions if/when needed. Preferably you have a nice conversation with them as they're doing it. NEVER just drop off your truck and come back later!! Last year I had a tire tech who was going to install a tire on a rim AFTER he'd cleaned the white walls off ...there was at least a quarter cup of water in the tire. I had turned to answer an email and he was about to put the tire on with the water inside the tire!! I put an emergency stop to it and made sure we removed the water and completely dried out the inside of the tire. That's the kind of thing I'm talking about. I could tell other stories. Point is, a guy can't turn his back on a tire tech for even a minute! Unless you know your tire tech personally and trust for sure he is a stickler for details. Even then I wouldn't leave the process unchaperoned.

Go to a shop which has a Road Force balancer (the best), by Hunter, which many/most shops have (but many don't use for normal tire balance jobs). Pay the extra to have it done. It will uncover any weaknesses, out-of-round tires, bent rim, wrong weights, hard-spot in the rubber ....or whatever. Once tires wear-in to bad weights or out-of-roundness, they're kind of set after a while. So do it sooner than later. If they StiLL don't find anything. have them put a dial indicator on the rims (on the vehicle) and check for wheel run-out. I bought a brand new OReilly's hub/bearing 2 yrs ago and it was pre-warped out of the box. And this wasn't the economy model either. I put the dial indicator on it before installing and it was .005" deflection at the outer edge of the hubface. SO... even perfectly balanced tires would be wobbling if I had installed it. (and give a shimmy). I took it back, they probably re-sold it, or it made it's way on ebay to some unsuspecting owner (maybe you??!). LOL Spend the $$ on Mopar stuff.

Of course have them check for worn suspension parts/components incl bad shocks.

Let us know what you find.

I don't have any vibration / shake issues.