Hi guys,
First time poster, but long time lurker. I’ve read many posts on this website while trying to figure out how to fix my 1994 Dodge Ram 1500 5.9L 4x4.

Currently I’m having problems with my truck, I’ll try to describe what is going on. I’ll also provide a link to a YouTube video so you can hear what’s going on. It’s not a great video, but at least you’ll be able to hear what it sounds like, kind of hard to describe with words. In this video I am not touching the gas pedal at all




So the truck starts up fine, I can let it idle for about 10 min and everything sounds and seems ok. Then once I put it in drive and go about 200 yards or so the engine starts backfiring, the RPMs go up and down, idling become erratic and if I come to a full stop with the truck in drive it will stall out if I don’t pepper the gas pedal. After driving it over 5 min, then it just wants to die so it’s been a while since I’ve attempted to drive it out of my neighborhood. It's not overheating.

I checked the codes using the key on-off method and got codes 37 and 51

This is not a daily driver and I have a 1 year old and a 3 year old daughter, so I haven’t had a lot of free time lately to work on the truck. It really hasn’t run “right” in a few years, but the past year or so it hasn’t been drive-able.

Over the past 6 months I have replaced the following:

• TPS sensor
• O2 sensor
• Idle Air Control Valve
• Spark Plugs & Wires
• Dist Cap and rotor
• Pickup Coil (the circle piece at bottom of distributor)
• Cleaned K&N air filter and entire air housing
• Cleaned the crap out of the throttle body, used new Fel Pro gasket when I replaced
• New water pump and Fel Pro gasket
• Thermostat and housing with gasket/RTV
• New plenum plate and bolts from Hughes with Fel Pro gasket, used Loctite on bolts – My plenum was nasty with oil and the inside of the intake manifold was gross too
• Cleaned the crap out of my intake manifold, again using Fel Pro gasket when reinstalling
• New double roller timing chain, cleaned cover really well, used Fel Pro gasket and crankshaft front seal
• PCV Valve
• New O-rings on fuel injectors and cleaned the injectors when I had the fuel rail off for the plenum
• Installed a block plate to “delete” the EGR…. I actually installed a new EGR a couple years ago too, but recently just blocked it off
• Emptied radiator during plenum/timing chain install and re-filled / burped it
• After pulling the intake and water pump off the truck, my transmission pan starting leaking, so I tighten up the bolts to spec and topped off the fluid with ATF+4

While doing all the above I watched so many YouTube videos, and read posts from this and other forums to ensure I was doing everything correctly. I have the Haynes book and the online more complex version. I’ve torqued every bolt to spec, used RTV where needed and if anything called for a gasket I used Fel Pro, etc...

The symptoms I mentioned at the start of my post were happening BEFORE I made all the repairs AND are still happening today. I’ve thrown just about every part I can think of at this truck and am ready to make it road worthy again.

Next things I plan on checking:

• Test fuel pressure on fuel rail
• Ensure plug wires are routed properly from dist to plug – Don’t think this would be a problem as I was having these issues before I touched the wires
• It also sounds like I have an exhaust leak, I’ll try to locate and correct that
• I have a new crank sensor that I plan on installing soon – I found where it goes, just need to move the transmission dipstick to get to the high bolt

Do you guys have any other suggestions on what I should take a look at to get this truck back on the road?

 

I get a oxy sensor lean condition for that code 51, you could check its output with a digital volt meter. This is from my Haynes manual. Although when you start a cold engine the sensor is not active. The code 37, is in the transmission:http://dodgeram.org/tech/dsl/trouble..._DTC_codes.htm.

 

Check the grounds on the engine, then wiring from the O2 sensor and transmission back toward the engine compartment.

37 Torque converter clutch solenoid CKT or park/neutral switch failure
51 Fuel system lean

The O2 and transmission wiring run up in the same harness towards the engine and use common ground points.

 

If it's running lean, and it sounds like it is, you need to figure out why:

1. Check for vacuum leaks. Does the engine run better at driving speeds than idle?
2. Dirty or malfunctioning injectors.
3. Fuel pressure at the rail.

I can't get to the video, but if it is surging without touching the gas pedal, start looking for your vacuum leak.

 

Thanks for the advice guys.

I think the transmission code is from the trans pan leaking and the truck being parked for so many months. I've tightened up the pan bolts to spec and topped off the fluid, but I'll continue to monitor it.

Never knew the o2 and transmission ran up the same wiring harness. I'll see if I find anything wrong there.

The o2 sensor is newish, I'll test the voltage running to the sensor.

Truck is surging without me touching the pedal.
I've looked for vacuum leaks, but I'll take another look for them again and see if I find any.
Injectors are nice and clean, I even installed new O-rings on them a week or so ago.
Fuel pressure on the rail I plan on testing out this weekend too.

Thanks again guys, I'll let you know what I find out

 

Maybe you and others can have a listen but to me it sounds it's running way rich. Which is why I'm thinking the ECU just "thinks" the engine runs lean and runs up the fuel trim to the max. That would also explain that it starts fine (need more fuel for that) but starts to stumble once warmed up.

 

man I feel your pain, I've had nothing but good luck with the 2nd gen ram's I've had but I had a particularly problematic older junky 01 nissan sentra I threw every part under the sun at and even got it tested and mechanics were stumped, I could never fix the random misfire it had, in the end, I think the engine was fried possibly. I tried in vain to get help online on dedicated forums but either they were outright dead or nobody bothered posting in the older nissan areas. Luckily this is a really nice site I found.

from what you've already changed which is a long list, I too would check fuel pressure, make sure of no vacuum leaks, and literally the only other two things I could think it could possibly be are the crankshaft sensor and/or the coolant temp sensor, they're about the only things left from process of elimination from all the other parts.

do you know what brand o2 sensor you used? OEM was NTK I believe, I heard anything besides NTK or Denso runs like garbage for these trucks.

best of luck. I've found these to be particularly hardy vehicles, I've only ever really needed to do general tuneup stuff and throw some decent tires on. On the bright side, when you do figure out what the problem is, the truck should be good to go for many years with all the fresh new parts on it.

edit: if the truck drives and shifts fine after you fix it, I'm not sure if I'd be very worried about that trans code, I was told in these pre OBD2 rams using the 46RH trans there's no electronics solenoids to even ever change out like I've heard and seen go bad on the newer 2nd gens using obd2, which often, changing out the solenoid could save a bunch of money over needing a whole new trans. When I checked for codes via the on/off 3 times method, I got 12, code 37 as well, and engine cold for too long, but I attributed that to just short trips that winter. per this link at the bottom, http://dodgeram.info/Engine-Gas/OBDI/pcm_fault_code.htm "NOTE #1 - From the 1995 TRUCK (Ram) manuals: the trailer towing package includes a transmission coolant temp sensor while the standard package doesn't. The fault code detection system is probably the same for both models. This could cause the low (no) voltage indication....no sensor to send any voltage."

mine drives and shifts fine at almost 226k miles, so I guess I just didn't have the towing package and there's literally no sensor to send data so the computer thinks it's bad

edit2: if the above parts/suggestion doesn't help, since you're in this deep already, a new ignition coil couldn't hurt. Although my dad's 98 ram has never needed it and my 95 looks like it has the original coil, nonetheless I bought a new one to throw in the glovebox for a spare last ditch roadside repair if ever needed.

 

The ECU thinks it's running lean because the O2 sensor is telling that there's too much O2 is in the exhaust. That, of course, forces more fuel into the mixture. If it maxes out, and still sees too much O2 in the exhaust, it tosses the code. I'm not very familiar with OBD1 engines, but it would be great to get on that truck with a bidirectional scanner and see what's really going on.

 

Ok, so as I was changing out the crank sensor I found a green line that was unplugged. I haven't looked through the manual yet to try and identify this line, but I have a good feeling this is the reason for my issues. At least I really hope this is the culprit.

I uploaded a video of the line to YouTube


Didn't realize there was music playing in the background, hoping they don't remove the video for copyright infringement like they've done in the past...

You guys have any idea where I need to plug the green tube/line in that's on top of the transmission behind the engine?


EDIT:

Well shoot. Just found this post, where someone was searching for the same thing...
https://dodgeforum.com/forum/2nd-gen...cuum-line.html

I guess that is not the problem.... Well I'm heading out now to crank her up and see if the crank sensor did the trick. Will report back later. Again I appreciate all the input.

 

Holy cow. So I purchased that crank sensor over a year ago and was just too lazy to install it. Installed it today and also installed an EGR block plate on the exhaust manifold to stop the exhaust leak.

I cranked it up, let it idle about 10 min. Ran it through the gears a few times while in park, checked the transmission fluid level and the dipstick was bone dry, so I added another 1/2 quart of ATF +4.... let it idle another 5 min. Then drove it around. After a few minutes I was expecting it to start stuttering and backfiring like it's done the past couple years. Well guess what, she drove perfectly! Well at least around the neighborhood, top speed might have been 30 MPH and drove for about 10 min with no issues at all. No stuttering, stalling, no RPMs up and down, no backfires....nothing unusual.

Wow, I think it's finally fixed. Next test is to see how she does driving around town and then on the highway. I'm thinking the transmission codes was just from the truck sitting and leaking transmission fluid. I tightened the pan bolts and topped off the trans, so I'll keep an eye on it and check codes again soon.

Thanks for everyone's help. The people that replied to my original post, and the most help I got was from reading old posts and I read so many of those.
If the truck acts up again I'll report back again.