Allpar Forums banner
1 - 15 of 15 Posts

·
Registered
Joined
·
15 Posts
Discussion Starter · #1 ·
Hi guys, (1500, 5.9L, Auto, 2WD, 136K miles)

Still having weirdness with the Ram, but have some more information. Starting from cold it is perfect, responsive and great to drive, cruise, overdrive-button and A/C work as expected.

After a perfect 20-mile run into town, park and shop for 30-minutes, come out and start and within a mile or so it is running rough. The A/C is permanently on no matter where the controls are set and the cruise and over-ride-button do not work.

A few miles later the Check Engine comes on. Checking codes they are a different bunch each time, usually four or more.

This morning instead of heading for town, I went the other way for 10-miles, turned around and drove into town and beyond, turned again and came back into town. Still perfect to drive after 60-miles. parked, turned it off for 5-minutes, started up and still prefect. Drove a a mile, parked for 15-minutes, this time on restart, rough running and all the maladies mentioned above. Idle is lumpy but mostly manages to stay alive.

Battery is good, load-tested by NAPA guys.
Fitted new terminals and soldered cable ends to all #6 and the other smaller wires to it.
I checked the temp of the PCM many times and always between 122-F and 124-F no matter if it was running well or not. Not the PCM overheating.
New distributor cap, rotor plugs and wires.
Checked Cam and crank position sensors, both good.

So, it is something that happens 15 minutes after driving, but before it cools down completely.

OK, gurus, where do I go from here. The great running from cold makes me want to keep at this it's not a scrap yard candidate yet.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #3 ·
It doesn't matter, they are random and often conflicting things (12, 51, 52, 53, 54, 55). We have yet to have a complete set of codes repeated.

When cold, the truck has run perfectly into town every morning for the past 3 weeks since this nonsense began. A short stop and restart is OK, 15-minutes or more, lumpy soup. Seriously doubt it is a code thing.
 

·
Got parts?
Joined
·
2,610 Posts
If the codes are different each time, I suspect a PCM problem. I had a similar problem in a Dakota; a small plastic piece was missing in the electric connector to the PCM, and it wouldn't seat properly, so I had to push it in periodically. You might check yours, and any other wiring connections under its hood.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #6 ·
If the codes are different each time, I suspect a PCM problem.
Thanks, I have actually checked the 3 connectors on the driver's side and the big one on the PCM. I even took the big one apart and pushed the captive washer on the bolt back a little so I could get some wiggle room in case it was a poor connection. I was able to wiggle it down as I tightened the bolt back in. I'd do a half turn, wiggle then another half turn.

I have been messing with computers and electornics for many many years and pretty sure it is not the PCM. But -- I have been wrong before. :)

If it was the PCM then surely in the past 21 daily trips when cold it would have misbehaved at least once. But that's the annoying part, it is perfect when cold. I have a small pocket oscilloscope I will put on the alternator and see if it is overly noisy when hot. It feeds into the PCM for Voltage regulation and may be getting things excited, but grasping at straws here.
 

·
Super Moderator
Joined
·
33,353 Posts
Sounds like a problem with thermal expansion and contraction, and the PCM or its connections are the logical place. Could be internal to the PCM.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #8 ·
Thanks, but getting both 51 and 52 in the same sequence makes no sense -- I believe. :) But an interesting thing one of your links. That 11-minutes might explain the engine light coming on after a few miles, but we would be home before the 48 were up. It's a weird thing from cold, but I will put in a new O2 sensor, I have one here somewhere. I just went and got the codes from this morning 12, 52, 32, 27, 55.

For 1986 and later models, code 51 is triggered when the engine has been running lean for more than 11 minutes, 55 seconds, as reported to the computer by the oxygen sensor (O2); and code 52 is triggered when the engine has been running rich for more than 11 minutes, 55 seconds. The power limited light will not be lit in either case.


If the condition which causes code 51 or 52 continues for four times the time it took to set the code (roughly 48 minutes), the engine will run in closed loop mode, which forces it to run rich, preventing it from running lean (running lean can cause severe damage). During closed loop, the logic module continues to monitor the O2 sensor.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #9 ·
Thanks, but that's why I checked the temp of the PCM. At the first stop after 60-perfect miles this morning it was 124, the second stop 125 then after the engine light came on I checked and 123.
 

·
Registered
Joined
·
730 Posts
Hi guys, (1500, 5.9L, Auto, 2WD, 136K miles)

Still having weirdness with the Ram, but have some more information. Starting from cold it is perfect, responsive and great to drive, cruise, overdrive-button and A/C work as expected.

After a perfect 20-mile run into town, park and shop for 30-minutes, come out and start and within a mile or so it is running rough. The A/C is permanently on no matter where the controls are set and the cruise and over-ride-button do not work.

A few miles later the Check Engine comes on. Checking codes they are a different bunch each time, usually four or more.

This morning instead of heading for town, I went the other way for 10-miles, turned around and drove into town and beyond, turned again and came back into town. Still perfect to drive after 60-miles. parked, turned it off for 5-minutes, started up and still prefect. Drove a a mile, parked for 15-minutes, this time on restart, rough running and all the maladies mentioned above. Idle is lumpy but mostly manages to stay alive.

Battery is good, load-tested by NAPA guys.
Fitted new terminals and soldered cable ends to all #6 and the other smaller wires to it.
I checked the temp of the PCM many times and always between 122-F and 124-F no matter if it was running well or not. Not the PCM overheating.
New distributor cap, rotor plugs and wires.
Checked Cam and crank position sensors, both good.

So, it is something that happens 15 minutes after driving, but before it cools down completely.

OK, gurus, where do I go from here. The great running from cold makes me want to keep at this it's not a scrap yard candidate yet.

Have you checked all of the vacuum lines and any connectors, to see if any are loose, cracked, separated, etc. I had a Dodge Durango with the 5.9 V-8, AWD and automatic. When it would warm up, it would run rough and set codes. I found a vacuum line split where it was attached to a metal nipple on the lower (front) side of the throttle body. Looking at the line, it looked good. When I pulled on it, it slipped off easily. I replaced it (and several other lines), and that solved my problem.
 

·
Super Moderator
Joined
·
33,353 Posts
Thanks, but that's why I checked the temp of the PCM. At the first stop after 60-perfect miles this morning it was 124, the second stop 125 then after the engine light came on I checked and 123.
If you're referring to my post on thermal expansion, your temperature measurements mean nothing. I'm referring solder joints or other connections opening and closing with thermal expansion and contraction, making contact while cold, but opening when hot. That's a classic solder joint failure.
 

·
Super Moderator
1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
Joined
·
23,627 Posts
Finding temperature-sensitive underhood components may involve 'chilling' the component before trying it again. I pitcher of ice water poured over the module after a hot-soak may offer clues. The internal PCM board and connector are supposed to be waterproof.

Getting rich and lean faults at the same time makes little sense. Test driving with a good scan tool can tell you fuel mixture and trim values. See if target idle matches actual idle. Some issues won't set fault codes. The Powertrain diagnostics handbook may help. They can be found and may pay for itself:
8169994008.jpg

The ignition coil mounted next to the exhaust manifold was known for heat-related damage after a few years. The intake manifold belly pan gasket was known for disintegrating and becoming an internal vacuum leak.

A new OEM O2 sensor would be better than installing an unknown O2 sensor.

Cruise control may not work with active fault codes. The 'ck eng' light may be out, but the codes are still stored. The A/C compressor may run in defrost and floor/defrost modes.

If there are no patterns or rhyme or reason for the fault codes you are getting, I may lean towards a PCM myself. Always diagnose first.
 

·
Registered
Joined
·
15 Posts
Discussion Starter · #13 ·
It's fixed and cost zero dollars and a few hours of my time. Lessons to be learned here guys. Conflicting codes is a good indication it is not in the codes.

How does one mark this as "Solved?"
 

·
Got parts?
Joined
·
2,610 Posts
How does one mark this as "Solved?"
If one of the posts described what caused your problem and how to fix it, there's a "Best Answer" box at the bottom right that you can click. Otherwise, you might share what the problem was and the steps you took to solve it; if someone else has a similar problem, this thread can be cited as a solution.
 
1 - 15 of 15 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top