Hi all. Strange thing going on with my 06 hemi qc 1500. It started doing this today and i've never seen it do this before.

I have an MDS led installed. Normally when i drive with light throttle in 3rd gear (auto) and up, the light comes on (MDS is on). Even when i coast, as long as my rpm is 1k or more, mds stays on.

Today however, as soon as i let off gas and coast, mds light turns off no matter what the rpm is or how fast im going.

Few things i checked is oil level - fine
Tire pressure- fine
Gas used is 93 octane

What else is going on?

 

Well, stop using the 93 octane - it's doing nothing except draining your wallet. I suspect that MDS will only engage when you're in 5th gear. Is it possible you have a bad connection to the indicator? Is it fully warmed up? MDS won't engage unless all the spinning pieces are warmed up. You didn't switch from 5W-20 did you?

 

Hi Mike. Let me answer all your questions:

I use 93 octane only because the manual states that it needs 91 octane as recommended. In Texas, we only have 87, 89, and 93 at all popular stations. So I was trying to at least meet the minimum requirements.

MDS kicks in at 2nd gear and up depending on load and throttle application. It used to ALWAYS engage while coasting in a 20 MPH school speed zone. It's now starting to act this way today were as soon as I let off the gas, it disengages.

While it is possible that I have a bad connection, it is improbable because as soon as I give it light throttle and wait a few seconds, MDS comes back on. I also checked the connection and it's solid.

Engine is fully warm and needle is in middle on temp gauge. Oil pressure is in middle too and had a recent oil change about few weeks ago.

I most certainly kept to 5w20 Castrol dino oil. Never switched from 5w20.

It is driving me crazy! It's almost like a software glitch (I'm a computer guy) so something must be causing the computer to take it off of MDS when no throttle is applied.

I appreciate your input. Can someone please help give me more things to look for?

 

I don't have a light indicator on my truck (08) however, my MDS always turns off when I let off the gas to coast... just my .02

 

What I"m saying is it has never done this before. I know not only from the light, but from the "tractor" noise you hear as you are coasting. It now gets out of MDS.

Anyone out there know what's going on?

 

I don't have an aswer for your MDS question but want to address this comment you made. Let me say right off the bat nothing I am saying is meant to be offensive, rude, mean spirited, etc... Just commenting!

I hear similar comments about premium fuel being recommended/needed in the HEMI quite often on forums like this and wonder where they come from? Dodge does not and has not recommended premium fuel in the HEMI 3rd Gen Rams. Definitely not in the owner's manual. The fuel octane rating comments in the manual have been the same basic thing from 03-08( 1500's ). I had an 04 and now have an 08 and it has stayed the exact same recommendation. I have looked it up for every year at times in these types of discussions and it is always the same.

In the 3rd Gen Ram owner's manuals Dodge recommends 89( mid grade )for optimum performance and fuel economy and 87 is listed as acceptable for the 5.7L HEMI. They actually say NOT to use premium fuel( 91+ octane )as it will provide no advantage over 87 and 89 and may even result in worse performance. So, whomever told you that you need 91 was mistaken and you have been wasting your money running premium. The member who told you that above is telling you the truth. Unless you have mod's like a tuner, or NOS, Super Charger, Cam, etc... that requires premium running anything but 87 or 89 in a HEMI is a waste of money.

Here is the exact info from a 2006 manual( got it online direct from Dodge ). I suggest you go look in your owner's manual to verify for yourself I am telling you factual things here( if your manual states 91+ octane is recommended please scan and post - something is wrong ). Stop wasting your money with that premium fuel. Run 89 if it makes you feel better or your truck gets slightly better MPG or performance( mine gets exactly the same on 87 and 89 )but just no need on a stock or slightly modd'ed HEMI( i.e. CAI and/or exhaust )for premium.

Again, I am NOT trying to be a jerk. Just hate to see people wasting their money like that. Also, if you decide to drop back to the actual recommended octane ratings of 87 or 89 I suggest a computer reset after running 93 for so long. Will hasten the adjustment to the new octane rating.

2006 Dodge Ram 1500 Owner's Manual
Starting And Operation
Page 356 - 357

Fuel Requirements:

 

Correct, but if you are using custom tuning like I am and have your timing adjusted for 93 octane then you get more power and better performance.

 

Hey bud. I really appreciate your input. I'm most certainly not offended at all, actually quite pleased to have you explain this to me.

To be honest, I guess I just misunderstood the book. I've owned other cars such as a civic si and acura TL type s that require 93 octane, so when I glanced over the manual and saw 89 as recommended and 87 as acceptable, I understood that to mean that you can use 87 sometimes, but stick to 89 and above.

I will now stop using 93 octane. Although I have to say that when I used 87, I did notice a drop in about 2 MPG. I use an app on my phone to record every single fill up so I can monitor MPG along with logging when my next maintenance will be. Very useful app called "Road Trip" on iphone, and Mileage on Android.

Thanks once again. I'm still baffled at the MDS not staying on while coasting. It was just fine 3 days ago, and just one morning doesn't want to do it. I'm considering pulling the battery to do an ECU reset. I'll check my oil level once again. Maybe it is extra sensitive on oil level.

Could a Fram oil filter cause this problem? My oil pressure is actually normal and higher than before my oil change when cold. I feel like I'm wasting gas because it won't coast in 4 cyl mode.

And thanks again NHHEMI, you really did make my day! I'm excited on the savings that I'll now see by using 87 octane.

 

There is nothing wrong with using higher quality fuels. Lower octanes do produce less power and do not burn as clean. There are many threads and guys who come in here with issues from using lower quality fuels including detonation issues with top land piston failures. Granted not every engine sees this but some do.

Besides, for the few cents it cost per gallon to run a higher grade of fuel, why not do it?

 

Well, I would say simply for savings. even if it's a few bucks at each fill up, it adds up each month, then each year.

But the fact of the matter is the manual states not to use higher than recommended fuel routinely. That's key for me to switch back down to 87.

So here's what I"m left with.

1. Reset PCM.
2. re-check oil level
3. use 87 octane.

Either one or combo of these hopefully will return the MDS behavior back to normal. I will update as I try these out.