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-   -   Help...Sudden loss of fuel economy! (http://www.ramforumz.com/showthread.php?t=128446)

B1500ram 12-17-2012 10:50 AM

Help...Sudden loss of fuel economy!
 
So i have recently had a sudden loss in fuel economy, i have an 03' 4.7 and it is sucking fuel like crazy. I usually can expect 300 miles or so to a tank and now i am at around 200. I have ran 2 tanks through, i have a k&n and thought that was dirty. It was but not too much and i gave it a good cleaning. Still having the problem though. Any ideas??!

I have heard maybe PCV valve, or 02 sensor? I have not cleaned the throttle body yet, and i am at 155,000 miles now.

Thanks folks... Brian

buzzvoodoo 12-17-2012 04:31 PM

Quote:

Originally Posted by B1500ram (Post 961970)
So i have recently had a sudden loss in fuel economy, i have an 03' 4.7 and it is sucking fuel like crazy. I usually can expect 300 miles or so to a tank and now i am at around 200. I have ran 2 tanks through, i have a k&n and thought that was dirty. It was but not too much and i gave it a good cleaning. Still having the problem though. Any ideas??!

I have heard maybe PCV valve, or 02 sensor? I have not cleaned the throttle body yet, and i am at 155,000 miles now.

Thanks folks... Brian

I just bought my 2002 4.7L a few days ago and I dont know very much about them yet. But I did ask my friend who is a mechanic for 40 years and owns his own shop now about the Sequential fuel injection system. I asked him if it was expensive to repair if it fails or if it was something that goes wrong often. He informed me that if the sequential fuel injection SFI or SEFI system does fail the car goes into limp mode and simply reverts back to its old form of method of injecting the gas into all the cylanders at the same time. He said I wont notice much of a change if that does happen but I will notice a loss in Gas Mileage.

Also maybe think about infesting in a locking gas cap. Maybe someone is syphoning gas out of your tank at night? 5 Gal gas can multiplied by 15 MPG = 75 less miles you will go on that tank.

B1500ram 12-23-2012 12:43 PM

Thanks for the advice, hopefully its a cheap fix, good idea on the siphoning but i am certain that is not happening. I will look into what you have said. As I said before, i hope its inexpensive. I may have to bite the bullet and take it in somewhere, until then, i am not driving it as far/often. Thanks again.

B1500ram 12-28-2012 02:50 PM

Still nothing new and still puzzled. As buzzvoodoo commented on siphoning, well, we have a foot of snow on the ground and i would be able to see foot prints if that were the case, but good call anyhow. The engine light is not on so i have no idea what it could be. I figure if it were serious wouldnt the check engine light be on? Any ideas or help is greatly appreciated. Thanks

Here is what i know:
-No current engine light.
-Clean K&N filter
-Gas MPG Before = 14
-Gas MPG Now = 7.5 !
-Tire pressure is good, no new tires, good tread

RamTech 12-28-2012 03:16 PM

Old O2 sensors can certainly have a negative effect on fuel economy because they're slow to respond to changes in the exhaust oxygen levels. A faulty MAP, TPS or coolant temp sensor may also be contributing to the problem.

B1500ram 12-29-2012 03:50 PM

Thanks so much, I was hoping you were going to comment on this one! Guy at the auto shop said if it were a faulty sensor I would get a light and code. But, I have suspected it could be an 02 sensor because the exhaust smells really rich. I guess I will change one thing at a time and try to rule things out. Thanks again for sure, its costly to drive at the moment. I will let all know how it works, considering i am probably not the first to have this issue.

tjbiker031 01-04-2013 07:27 PM

Any updates? I'm interested to see if new o2 sensors helped?

Cobra7077 01-07-2013 11:28 AM

I have a 03 ram with the 4.7.... I drove her from Montana to New York a few days ago... It was getting around 10 mpg and I have the efan mod and cleaned my tb before I left. I also have a soft tonneau cover.... After i got to NY I gt a p0601 code saying my pcm had integral error... So went to advance auto ordered a used from a parts yard for 185 bucks and now it's back up to 16 mpg. My code scanner wouldn't read the code but the one at advance did... Just FYI.

B1500ram 01-23-2013 12:49 PM

alright guys, thanks for all advice. NAPA told me that the O2 sensor, or any sensor for that matter would flash a code. All I have is P0463 or something, it means the voltage to the fuel sending unit is too high and my fuel gauge has been inconsistent for about 4 years. I dont think this is related to fuel economy because i havent noticed any problems untill i made this post.

They recomended a fuel cleaner called B&K 400 (25$ !). I think it is helping, last time i checked i am up to 10.5 mpg, still not where i want to be. I have not replaced sensors and i am still trouble shooting. I may replace the O2's but it would be about 100 bucks to do so, just want to make sure that is the problem before i waste money on not fixing the problem. Thanks, all advice is welcome! Keep you all informed as this progresses....

snrusnak 01-23-2013 01:00 PM

It is possible that the O2 sensor can be faulty and not trigger a check engine light. If you do replace the O2 sensors, only replace the upstream ones(ones closest to the engine). Do not waste the money replacing the downstream sensors(in or after the catalytic converter(s)) as they are just for emissions and will not effect performance or mpg.

You should be getting closer to ~15mpg.

Also, looks like your already bought that fuel cleaner, but I wouldn't waste any more money on that. If anything just run some sea foam through the engine, but this isn't your issue.


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