2009 Ram 1500 5.7 MDS - weird #5 misfire problem

[cuda341]

I have a weird thing happening at 135K miles, with a clean well-maintained, original-owner 2009 Ram 1500 Hemi MDS. It’s actually two things that are probably related:

1. After a cold start, it runs fine. I drive about 1 minute and if/when it kicks into eco/MDS mode, it runs poorly (95% sure due to cyl #5 - see below) until I either pull over and turn off the ignition completely, and restart, or until it warms up over ~165F or higher. This NEVER happens if I start out in Tow/Haul mode or with shifter in a lower gear i.e. 5th, in order to keep it from going into eco/MDS mode until warmed up (or over 165F). Once it’s warmed up, I can use eco/MDS mode just fine, and it purrs along great – like new,
2. BUT under normal operating temp, if I put relatively heavy throttle into it, typically on the highway, somewhere between 3-4K RPM, it throws a P0305 #5 cyl misfire code. When I let up, the light usually goes away pretty quickly. But this will repeat fairly consistently under heavier throttle, and when it’s occurring, I can usually feel the roughness until it clears.

This original 5.7 has new spark plugs and I tried swapping the #5 coil pack with a new NGK, even though the original still looks new, as do all the rest. Since turning off the ignition and restarting seems to clear either condition, it makes me think this is computer related. The code is always #5 cyl, and she doesn’t seem to be burning any oil or coolant (via head gasket), so other than possibly the injector, I’m still scratching my head at this. If I remember to turn on Tow/Haul or keep it out of eco mode until she warms up, as well as take it easier when passing or using the on-ramp, she runs fantastic like a sewing machine all day long. No tick noise - ever. I’d love to get thoughts on this and what I can try. Thanks in advance!

 

[Wild one]

If nothing external pans out,and you've done a compression test on all 8 cylinders,pull the drivers side valve cover and check and see if #5 rockers are moving as much as the rest,and check #5 over for a broken valve spring.Hopefully you don't have a bad cam/lifter,but you're right in the milege range where they do start to go bad

 

[cuda341]

Thanks for the input. What puzzles me is the fact that it runs so well otherwise. Wouldn't an internal component failure like a broken valve spring, cam/lifter be constant and rather noticeable most of the time?

 

[Black1500Ram]

Since it’s an 09 what oil are you using?
The earlier rams could get MDS issues with wrong viscosity.

Doubtful but something to check

Edit - actually cyl 5 is a non MDS cylinder.

 

[cuda341]

I've always used synthetic 5W20 per original specs.

 

[Black1500Ram]

Yeah won’t be that due to it being a non MDs cylinder anyway.

You can test moving the injector to a new cylinder and see if the misfire follows.

 

[cuda341]

Yeah won’t be that due to it being a non MDs cylinder anyway.

You can test moving the injector to a new cylinder and see if the misfire follows.

Great idea - thanks!

 

[Burla]

When cams go out the tend to go out when oil is warm and you will find when the engine is cold you often can drive, so to answer your question about all the time it is no.

However, the fact it doesn't happen in tow haul this might be the unicorn rare MDS issue. So why not tune MDS out of the truck or just drive in tow haul from now on? If it EVER happens when you are in TH, then it wouldn't be an MDS issue. Try it for a week or better and report.

 

[cuda341]

When cams go out the tend to go out when oil is warm and you will find when the engine is cold you often can drive, so to answer your question about all the time it is no.

However, the fact it doesn't happen in tow haul this might be the unicorn rare MDS issue. So why not tune MDS out of the truck or just drive in tow haul from now on? If it EVER happens when you are in TH, then it wouldn't be an MDS issue. Try it for a week or better and report.

Thanks, I will try this as well.

 

[Wild one]

Thanks for the input. What puzzles me is the fact that it runs so well otherwise. Wouldn't an internal component failure like a broken valve spring, cam/lifter be constant and rather noticeable most of the time?

Broken valve spring should be noticable,but alot of times when a cams going south,it won't make much noise,until it's really bad. Before you get carried away with putting a bunch more miles on it,i'd pull the drivers side valve cover,and check #5 over,if the cams going bad,and you keep on driving it,there's a good probability you'll hurt the engine beyond being able to just get away with a cam and new lifters.Your truck,your call,but if it was my truck,i'd be investigating under the valve covers before putting a bunch more miles on it,i'd also probably jerk the intake off,and check the VVT solenoids screen over for metal particles.That's just me though,you do whatever you feel you're comfortable with.

 

[cuda341]

Broken valve spring should be noticable,but alot of times when a cams going south,it won't make much noise,until it's really bad. Before you get carried away with putting a bunch more miles on it,i'd pull the drivers side valve cover,and check #5 over,if the cams going bad,and you keep on driving it,there's a good probability you'll hurt the engine beyond being able to just get away with a cam and new lifters.Your truck,your call,but if it was my truck,i'd be investigating under the valve covers before putting a bunch more miles on it,i'd also probably jerk the intake off,and check the VVT solenoids screen over for metal particles.That's just me though,you do whatever you feel you're comfortable with.

Good info/insight, thanks. I think I'm about at that point...

 

[cuda341]

When cams go out the tend to go out when oil is warm and you will find when the engine is cold you often can drive, so to answer your question about all the time it is no.

However, the fact it doesn't happen in tow haul this might be the unicorn rare MDS issue. So why not tune MDS out of the truck or just drive in tow haul from now on? If it EVER happens when you are in TH, then it wouldn't be an MDS issue. Try it for a week or better and report.

Well, I can clarify that condition 1 in my initial description only happens when MDS is not disabled, so Tow/Haul will prevent that.

In condition 2, I tend to get the misfire code regardless, under higher RPMs/acceleration. If I never put my foot into it, day to day, I never get the misfire described in 2.

 

[04fxdwgi]

Have the plugs ever been changed?

 

[cuda341]

Have the plugs ever been changed?

Yes, all new spark plugs.

 

[Scott06HEMI]

Any time I have a cyl misfire I start by swapping the coil pack from the misfire cyl over with a different to see if the problem moves.

 

[pscarbor]

May be totally unrelated but - I have a 2004 Ram 1500 5.7, has become sort of a project car for me. It's currently running great except I suspect a driver's side exhaust manifold leak. Its on my "to do" list.

Anyway a few months back I decided to try a can of Seafoam in the gas. I put in the big can - way too much but why read the instructions? That seemed to smooth things out a bit and so at 1/2 tank I dumped another big can of Seafoam in.

After about fifty miles I got that same MDS failure code, except mine was cylinder 6 I think. Truck still ran ok. I cleared the code and drove it; after forty or fifty miles the MDS code came back and then kept coming back. At 1/2 tank I topped off with 91 octane non ethanol and haven't had the code since. I finally read the instructions on the Seafoam can and found out that I was putting like, three times too much in my gas.

So question: Did you put anything in your gas? Seafoam or something similar? Could it be just a bad batch of gas?

 

[cuda341]

May be totally unrelated but - I have a 2004 Ram 1500 5.7, has become sort of a project car for me. It's currently running great except I suspect a driver's side exhaust manifold leak. Its on my "to do" list.

Anyway a few months back I decided to try a can of Seafoam in the gas. I put in the big can - way too much but why read the instructions? That seemed to smooth things out a bit and so at 1/2 tank I dumped another big can of Seafoam in.

After about fifty miles I got that same MDS failure code, except mine was cylinder 6 I think. Truck still ran ok. I cleared the code and drove it; after forty or fifty miles the MDS code came back and then kept coming back. At 1/2 tank I topped off with 91 octane non ethanol and haven't had the code since. I finally read the instructions on the Seafoam can and found out that I was putting like, three times too much in my gas.

So question: Did you put anything in your gas? Seafoam or something similar? Could it be just a bad batch of gas?

No additives, but thanks for the thought. In fact, I'm always been pretty particular about using BP/Amoco fuel 89 octane or above. And this has been happening for a few tanks of gas now.

 

[Dusty]

Any time I have a cyl misfire I start by swapping the coil pack from the misfire cyl over with a different to see if the problem moves.

Which is very easy to do on a Hemi truck engine.

Regards,
Dusty
2019 Ram 1500 Billet Silver Laramie Quad Cab 2WD, 5.7 Hemi, 8HP75, 3.21 axle, 33-gallon fuel tank, 18” wheels. Build Date: 3 June 2018. Now at 110857 miles.

 

[Daw14]

Lots of counterfeit plugs out there lately .