2005 Ram 1500 ThunderRoad 4.7 Bad Gas Mileage

[Michael Bennett]

Hello everyone, I am new to the group today. I have a 2005 Ram 1500 4.7 Non Flex Fuel. I am getting 10.5mpg both on highway, and city. I have replaced all the spark plugs with platinum plugs, replaced map sensor, replaced IAC Motor, airfilter, and nothing effects the mileage. Please help!

 

[Fast69Mopar]

If you are experiencing poor fuel economy, there are a few things I would do first.

How long has the truck been getting this fuel economy?

Was it ever consistently higher?

If any of your maintenance has not made a change, it's time to get a scan tool connected to this truck and take a look at the oxygen sensors and the short term and long term fuel trims.

Those pieces of data will give you a big picture of what is really going on with the motor.

What speed do you drive on the interstates and highways?

What RPM do you cruise at?

Do you run a larger/taller than stock tire?

 

[Bloody_Knuckles]

Brakes dragging?

 

[Michael Bennett]

Fast69Mopar when I bought the truck I was getting 12.6mpg. As of today I am down too 10.5 no matter if its HW or City. I have already replaced Bank 2 Sensor 2 for the O2 sensors. Scan tool has shown me nothing out of the ordinary. As far as highway driving speeds most of the posted speed limit is 70mph, so I am usually always 5mph over the posted limit. Most times the cruise control is on. I saw in another forum somewhere that a guy was having the same issue I am having. He stated in his post that his timing chains had stretched which caused the timing to retard, which gave him bad gas mileage. He said after he replaced the chains and quides that he was getting 15-17mpg HW. Makes no sense to me though, timing chains don't stretch.

 

[Bloody_Knuckles]

Yes, they do. Ever had a chain driven motorcycle or chainsaw? They have an adjustment because they stretch. Chains can only pull so a stretched chain means retarded timing on the valves and ignition.

 

[Fast69Mopar]

Fast69Mopar when I bought the truck I was getting 12.6mpg. As of today I am down too 10.5 no matter if its HW or City. I have already replaced Bank 2 Sensor 2 for the O2 sensors. Scan tool has shown me nothing out of the ordinary. As far as highway driving speeds most of the posted speed limit is 70mph, so I am usually always 5mph over the posted limit. Most times the cruise control is on. I saw in another forum somewhere that a guy was having the same issue I am having. He stated in his post that his timing chains had stretched which caused the timing to retard, which gave him bad gas mileage. He said after he replaced the chains and quides that he was getting 15-17mpg HW. Makes no sense to me though, timing chains don't stretch.

4.7, 5.7, 3.9, 5.9 etc. timing chains can and will stretch, especially 4.7 chains. I have replaced way too many 4.7 timing chains along with tensioners and guides.

Does your scan tool have the data capability to show you the timing?

We could look at the base timing at idle and the total advance while cruising. If the timing was an issue we would see it in the data on the scan tool.

How many miles are on this engine?

Has the front cover ever been off? Or the rocker covers?

This is a two wheel drive model, correct?

What RPM are you cruising at while running 70mph?

 

[Michael Bennett]

Fast69Mopar the truck currently has 206,000 on it. When cruising at 75mph I am at about 2,000rpm, 2,200rpm. And yes my scan tool will show timing.

 

[dhay13]

Timing chains absolutely stretch.

I had a 2007 Thunder Road with 4.7 and 3.92's. I bought it new and was averaging 11.9 MPG when I was working close to home. When I changed jobs and was doing more highway driving I was averaging 14.5. When I traded it in it had 47,000 miles and I was still averaging about 14.5. I will say that my 2013 with a 5.7 I bought new and was averaging about 14-15 in town but when I traded it in it had 67,000 miles and I was averaging about 12. Had the dealer do a tune-up at 60,000 and no better. Not sure why it dropped so much but my 2018 2500 6.4 gets the same MPG my 2013 1500 got.

 

[Fast69Mopar]

Fast69Mopar the truck currently has 206,000 on it. When cruising at 75mph I am at about 2,000rpm, 2,200rpm. And yes my scan tool will show timing.

Get the engine to normal operating temp and let it idle. Connect your scan tool and see what the base timing is at idle in park.

Next, start driving and monitor the timing when you are at different road speeds. Do 30mph, 55mph, 65mph, 70mph and 75mph.

If there is a timing issue, we can see it in the scan tool data while at a steady cruise with a steady load on the engine. The second place it can be seen is during wide open throttle acceleration. Under WOT, the timing will be up and down when it should be steady.

At 200,000+ miles I can gaurantee there is some slack in the chains. The oil pressurized tensioners can only take up so much slack before they reach their full travel limit.

 

[fastf]

If the timing chain hasn't been changed out and that many miles on that engine it must likely the timing chain too.The thing you must know no dodge aka ram get fantastic mileage I have had a bunch over the years.