95 RAM 2500 v10 - Mileage issue

Ok, just in case it can shorten my trying to figure out what's going on, I'll ask for more help


Situation, my truck was getting about 10mpg (average city/highway - even when hauling 4 wheelers around and fishing boat). Then 'out of the blue' it got 5mpg (there was 'bad gas' (every blend MUST contain ethanol) reported by refiner in our area - SE MN) and I wrote that off. Then I was constantly getting 7 to 7.5 mpg. NEVER had gotten that low - even with the 'winter blend' ethanol crap that has to be sold around here. I went over to WI and put in non-ethanol premium for two FULL tanks. Other thing I've noticed is that there is a bit of 'stuttering' when at about 1800rpm at 50ish mph. It seems to be 'just after' shifting into the gear (my speedo is about 3mph off compared to multiple GPS readings, and I can't seem to find a reason for that, so mph is 'close'). It only happens at that point in the shifting cycle (and I usually notice it on acceleration, not deceleration). It's a significant enough 'shutter' to rattle and empty pop can in the can holder above the radio. It wasn't noticed by brother in law in passenger seat until I asked him what it was about. I had transmission slipping in my blazer, but this doesn't have the rpm needle jumping at all so I don't think that's an issue. It doesn't go away with any combination of gas and additives - if that matters. I've put in fuel injector additive to clean it (Lucas stuff), put new NGK iridium plugs in all around, put in some Sea Foam in both full tanks. *edit* - Adding to that, if I keep it steady at that speed and rpm, it'll just keep 'stuttering' as long as I can hold it in the 'sweet spot'. 100/200 rpm higher and it stops. *end edit*

The truck has lost that 'kick' during quick acceleration (though I don't do that very often - just to test). All fluids are up to spec (oil, trannie) and holding well - just have my brake issue in another post. The wheel shakes a little when this happens if I concentrate on it enough. It's not anything that I really notice UNLESS I'm trying to find all the symptoms. It does not affect the steering - no pulling in any direction, no swerving or anything.

After the plugs, I'm now starting to think it may be cat converters choking off the system or something. I did notice that while out on the farm hunting that it killed two separate times/different days after slow 3 to 5 minute drives at night (about 30-40 degrees) to pick everyone up from the drop off points. It rarely has less than 1/2 tank in it (unless I want to push an entirely different supplier's gas / octane through it for tests). I did notice today that it sputtered and stalled while at idle and EVERY stop sign on my test drive today (but it has about 1/8th tank of fuel - going to go to WI again and get some more non-ethanol premium in her tonight).


Any ideas of what to check (and how to, as I'm just learning this stuff as I go) are greatly appreciated. Thanks in advance for your time and help!

Hmmmmmm got an interesting issue there. Now I'm not sure on the v10. But the v8 has a bad plenum gasket and the syptoms are very similar. But you say you aren't loosing oil so makes me think that maybe it's an intake gasket or something. Take some starting fluid and spray lightly around the intake. If the engine revs up a little concentrate on that spot. If you can squirt the stuff on the gasket and the engine raises rpm every time. Think you may have found your culprit. But this is just a guess.

Thanks, I'll give that a try!

I'm sorry for not updating the situation in such a long time.

I got busy having to look for work so everything else too priority over this. Been living with that bad mileage since..ouch.

Anyway, I did spray starter fluid around the entire front and side of the engine, no increased rpm. I did this on three separate occasions, twice by myself and then once with brother in law watching the tach.

I took the truck in to see if there were any codes (finally found someone in the town that would have an non-obd II reader available for not too much money). There were no codes what-so-ever stored in the computer. The Maint light is still on, so that must only be able to be reset when the emission system is 'tested'? I don't know, I've lived with it for a bit over a year, so I'll keep doing so.

I've run three straight tanks of the regular unleaded fuel (no ethanol, off road variety in MN) through the beast and nothing changed.

It's only stalled out twice since this original post, both times after being driven for awhile (engine has reached its standard operating temp).

The only new thing that I sense is that something is amiss with the shifting. The stuttering isn't nearly as measurable any longer, but it does seem to not shift at the right times. Seems that 2nd to 3rd gets 'drawn out' longer than it should at steady acceleration. Actually, the shift point is hitting just at 5mph over the 30mph speed limit in town here..so if I don't go that 5th mile over (or let up on the gas pedal for a second) it feels to me like it's very high in the rpm level (if I let off gas pedal for more than a secon, it's like downshifting a motorcycle and it slows down quickly w/o hitting the brakes). Once it kicks up into 3rd, I don't notice anything happening on the way back 'down' the gear cycle. If I'm stopped at a stop light on the highway, and accelerate at a higher than normal rate, I don't notice anything because I'm through that 30-35mph speed before I can feel it 'over revving' I think.

Does this V10 get shifted on speed or rpm? I did put a new speed sensor in when I bought the truck because the speedo didn't work a that time. Now, as I've said, it's always working but just 3mph off the gps at 55mph. 3mph is pretty consistent all the way up to that point too.

I'm wondering if it's time to get new (better) plugs in it and replace the plug wires and any other parts?

The service guy told me that if it were misfiring it should have codes. If it was the cat converters, it would throw codes and if it were the O2 sensors it'd have codes too.

Any ideas are greatly appreciated. I don't want to see 5.00 / gal for gas this summer and still be getting 5.5 to 7 mpg

Have you pulled your vavle covers and checked for loose rockers? When you pulled the plugs how did they look? Have you done a compression check? Could you have an injector stuck open or closed? When was the last time you did a tranny fluid change? Did you change the filter when you did it? Also IF it is a clogged cat does it sound quieter?

The plugs didn't look too bad; they weren't scorched or anything. I was told, when I bought it about a year ago, that the tranny was flushed and a new filter installed about 3 months before they sold it (they sold it because the father just purchased an old truck that they wanted to restore and needed some cash. Both were in the workshop when I went to buy it. I didn't know them, but the shop was legit so I tended to trust them. All trans fluid levels have been good the three times I've checked it over the year).

I've not done a compression test, what should it be? I have a compression test kit for my smaller toys so I'm sure I can find a fitting somewhere Same with the other toys, better to have a bit low if they are all the same (ish) amount than have 5 or 6 right on and others low?

How would I check to see if an injector was stuck open? I've looked at the exhaust and it doesn't 'smell' any different. There looks to be a good 'flow' coming out the back end, but I'm not sure what it should be. I don't have any residue on my hand when I hold it in the exhaust stream.

As far as it sounding 'quieter', it's never 'rumbled' but it does sound like it's got an exhaust leak somewhere (it now has a very steady 'pffft....pffft....pffft....pffft' sound that I don't recall noticing before the mileage reduction (maybe I didn't pay attention for anything then though). I hear it more in the cab than from outside the vehicle, if that matters. I also, when starting the vehicle, get an exhaust smell in the cab when the defrost is on. Only defrost though. I don't get it when the vent or recirculate is chosen. Those 'crazy' vents may have something to do with it though too.

Thanks for the quick reply. I'll try to get brother in law over here to help pull the covers and check for loose rockers. (I've never done that and trust he'd know how to tell if they are loose or not). Appreciate the ideas and guidance while I learn this stuff.

Here's my guesses based on info you've presented.

1.Converter clogging up (power/mileage loss)

2. Does a V-10 have an IAC (idle air control)? Sounds like it needs cleaning or replaced (stuttering at idle)

3 TPS. (Throttle position sensor) On our V-8 trucks this can cause stuttering/surging at steady speeds. I don't believe your 95 has a VSS (variable speed sensor) on the tranny but if you can check by looking. If you have a speedometer cable it doesn't.

4. O-2 sensors. If you've never done them and have over 100k miles on your truck, they need to be replaced.

You can also have a shop test your converter(s) with temp sensor...if the converter is hot at the inlet and cool at the outlet by too many degrees it needs replaced.

Thanks for the reply Okiespaniel.

1. Converter? Not familiar with that
2. Not sure, I'll find it in my shop manual and check if it does
3. TPS, yes it does have that, I replaced it right away to fix the speedo jumping around and sitting at 0.
4. I thought O2 sensors too, but the guy at shop told me there'd be codes in the computer if it were that, cat converter, misfire...I'd driven with the poor mileage since Oct 2010 so he was quite sure something should have registered by that time. But they are easy to get at from the pit, so I may as well change them out too as I don't know when they were replaced and I've got about 120k miles now.

Thanks for the help, it's appreciated greatly.

I tried to break it all down for you to make it easier.

CaptnTony said:

The plugs didn't look too bad; they weren't scorched or anything. I was told, when I bought it about a year ago, that the tranny was flushed and a new filter installed about 3 months before they sold it (they sold it because the father just purchased an old truck that they wanted to restore and needed some cash. Both were in the workshop when I went to buy it. I didn't know them, but the shop was legit so I tended to trust them. All trans fluid levels have been good the three times I've checked it over the year).

Alot of people recommend against tranny flushes. Because it will bring the junk in the pan up in the tranny. Most go with a drain and filter change.

I've not done a compression test, what should it be? I have a compression test kit for my smaller toys so I'm sure I can find a fitting somewhere Same with the other toys, better to have a bit low if they are all the same (ish) amount than have 5 or 6 right on and others low?

I'm not for sure where it should be on a v10. There is alot of different variables with that will decide where your compression is. IE cam pistions etc. Look for the pressures being close, a good rule of thumb is that all pistons be around 10% of each other. Like if a piston is a 150 psi you want all your pistons to be with in 10% of that piston

How would I check to see if an injector was stuck open? I've looked at the exhaust and it doesn't 'smell' any different. There looks to be a good 'flow' coming out the back end, but I'm not sure what it should be. I don't have any residue on my hand when I hold it in the exhaust stream.

I'm not really sure how to check for a stuck injector I'm sure someone will chime in. I have alot more experance with carbs.

As far as it sounding 'quieter', it's never 'rumbled' but it does sound like it's got an exhaust leak somewhere (it now has a very steady 'pffft....pffft....pffft....pffft' sound that I don't recall noticing before the mileage reduction (maybe I didn't pay attention for anything then though). I hear it more in the cab than from outside the vehicle, if that matters. I also, when starting the vehicle, get an exhaust smell in the cab when the defrost is on. Only defrost though. I don't get it when the vent or recirculate is chosen. Those 'crazy' vents may have something to do with it though too.

I would check where the exhaust manifolds and exhaust pipe connect. They could be loose. You may have a rusted out pipe.

Thanks for the quick reply. I'll try to get brother in law over here to help pull the covers and check for loose rockers. (I've never done that and trust he'd know how to tell if they are loose or not). Appreciate the ideas and guidance while I learn this stuff.

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CaptnTony said:

Thanks for the reply Okiespaniel.

1. Converter? Not familiar with that
He is refereing to the catalytic converter.

2. Not sure, I'll find it in my shop manual and check if it does
3. TPS, yes it does have that, I replaced it right away to fix the speedo jumping around and sitting at 0.
4. I thought O2 sensors too, but the guy at shop told me there'd be codes in the computer if it were that, cat converter, misfire...I'd driven with the poor mileage since Oct 2010 so he was quite sure something should have registered by that time. But they are easy to get at from the pit, so I may as well change them out too as I don't know when they were replaced and I've got about 120k miles now.

That's not always true. You could have a ghost code. Which means it's throwing a code but not setting of the check engine light. A good way to check is take your key turn it to the on postion then off then on then off then on. Your check engine light will start flashing. Count the flashes. If I remember correct it will go 1 flash then 2 flashes. That means the sequance is starting. If there is a code it will flash somemore. For example I think an 02 sensor code is like 21. So after the 1 then 2 flash it would flash 2 times then pause then flash 1 time. When its finshed it will flash 5 times then 5 times again. You could have a bad sensor. I had one on mine it threw a ghost code. When I replaced it I got a big boost in mileage.


Hope this helped

Thanks for the help, it's appreciated greatly.

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