Rough Idle, Poor Mileage and Weak Acceleration

[Chris Doherty]

Hi,

I have a 2012 Ram 1500 5.7L. About a month ago I had my spark plugs changed. I also had the coils changed. Right afterwards I started experiencing very poor gas mileage. Went from 16mpg on the highway to less than 12. It was also running a little rougher than usual. I thought it may be a bad plug. I pushed it hard to see if I could get the check engine light to come on. I did. Got a PO308 Misfire cylinder 8 message. I took it back to the mechanic who put in the plugs, and he told me I needed a new camshaft and lifters. I took his word for it (since I had just replaced the plugs and coils) and did that replacement. Got my truck back yesterday and Im still seeing the crappy gas mileage, rough idle and acceleration that seems to be more sluggish than normal. The check engine light has not returned after replacing the cam and lifters. But I haven't pushed it like I did a month ago. I replaced the spark plugs with NGK 92174. Ive read that you want the original copper. And that is what I thought I bought. Did I get the wrong ones? Could these spark plugs be the culprit? I have a K&N Air filter that was cleaned a few months ago. Does anyone have any suggestions as to how to diagnose where these issues are coming from and where I should start looking?

Thanks

Chris

 

[Karlsweg]

I’ve heard of people having problems with them. I never used anything but the champions and never had a problem. If they were the plugs you changed over to and your mpg went down then I would say that’s where to look first!

 

[onemc4you]

Mechanic must have cut a vacuum hose . I would take it to the dealer. That mechanic sucks!!


Sent from my iPhone using Tapatalk

 

[Kap1]

Others may have some good suggestions

Have you tried taking it back to mechanic who did the repair and asking him to double check everything regarding your concerns ? If there's no Cel then it's hard to argue something definitive, so far it's just your opinion which is subjective.

How much was the cam and lifters? How many miles?

 

[Kap1]

Mechanic must have cut a vacuum hose . I would take it to the dealer. That mechanic sucks!!


Sent from my iPhone using Tapatalk

Don't ever take an out of warranty truck to the dealer, you'll get Uber screwed. Find another reputable local shop if anything

 

[Compuls1ve]

I would look for a vacuum leak, or maybe replace the MAP sensor. They can slowly fail and not throw a CEL

 

[Chris Doherty]

Have you tried taking it back to mechanic who did the repair and asking him to double check everything regarding your concerns ? If there's no Cel then it's hard to argue something definitive, so far it's just your opinion which is subjective.

How much was the cam and lifters? How many miles?[/QUOTE]


My mechanic told me it was running fine. It is very subjective, except for the gas mileage. I notice the difference in how it drives and accelerates, but not sure if someone who didn't fully know the before and after would notice. But the gas mileage is 25-30% worse than it was a month ago. I track my mileage as opposed to looking at what the computer says, so I know exactly when something is not as it should be.

I spent around $800 on the cam and lifters. It has 215,000 miles on it.

 

[crackerjack1957]

When I picked it up, he told me it was driving well. I notice the difference from how it originally drove and of course the mileage. Not sure if someone else who is not fami



My mechanic told me it was running fine. It is very subjective, except for the gas mileage. I notice the difference in how it drives and accelerates, but not sure if someone who didn't fully know the before and after would notice. But the gas mileage is 25-30% worse than it was a month ago. I track my mileage as opposed to looking at what the computer says, so I know exactly when something is not as it should be.

I spent around $800 on the cam and lifters. It has 215,000 miles on it.

Did they replace timing chain & components?
That many miles they should have.
No more labor charge just cost of parts.

 

[Chris Doherty]

Did they replace timing chain & components?
That many miles they should have.
No more labor charge just cost of parts.

yes, I had the timing chain replaced. There was no extra labor charged.

 

[Musky Mike]

Sometime the oil from the filter can cake up the map sensor, would be easy and quick to clean or change it and see if that helps.

 

[Kap1]

$800 for everything or just parts? That kind of job cost about $3k where I live

 

[crackerjack1957]

Have a feeling something wasn't done correctly on rebuild or sensor was damaged but you need codes to troubleshoot.......do you know of anyone in your area that is good at data logging.
If you are in NC I would recommend Petty's Garage in Randleman.

 

[HammerHead]

I think I read somewhere that the coil packs changed in 2014 along with the spark plugs. That could be the issue; I'd double check your service invoice and compare those parts to what the dealership recommends for the year of your truck.
$800 for cam and lifters sounds like BS, I would ask to see my cam to verify the damage.