Hey guys/gals. I have been having this issue that comes and goes, mostly under very low throttle or idling. The RPM’s will barley move up maybe 200 rpms very briefly. My fuel pressure stays steady at 17 PSI. The below video is what I am speaking of. As you can see, and this is the first time this has happened, the check engine light came on. My dad has a scanner I can plug in to read the code, however any ideas at what might be the possible issue. Thanks. 

[video]

 

I also just noticed my temp gauge surges as well and then drops to zero after watching the video. 

Edited March 23, 20187 yr by Red Rambler

23 minutes ago, Mopar1973Man said:

Bingo... Frequency range is only 50 to 60 Hz. 

Given that the range was up/down and all over the place I am going to buy a new alternator as the stock one seems to be a major issue with so many trucks. Some seem to be at much lower miles than others, but they are quite old and many heater grid cycles applied.

Like mine went a whole 10 years before the OEM alternator failed. Now I can't keep an alternator unless I ditch the grid heaters. 

16 minutes ago, Mopar1973Man said:

Like mine went a whole 10 years before the OEM alternator failed. Now I can't keep an alternator unless I ditch the grid heaters. 

I am going to unhook the grid heaters when I can, that's for sure. Are you seeing any other weird electronic issues like mine when your alternator starts going? I have never had any Overdrive issues or anything else. I am just worried if I dont get a new alternator it might wipe out my down stream electronics.

 

The big brother to my multimeter goes way higher on the frequency range.

 

Edited April 4, 20187 yr by Red Rambler

I was able to take some time today and put on my new nations alternator and do the ground wire mod. So far after a few miles I am happy to report my idle surge has not reared its head. I need to get my dads fluke meter to test the new alternator. 

My crush splice was located here 

 

trophy of the day

So what is this alternator rated for amps compared to the stock one?

 

Did you also have to change any other wiring  from the alternator besides what you mentioned above or is stock setup good enough to handle this one?

 

And what does a nation's alternator cost compared to the typical stock rebuilds?

 

I'm glad to hear your truck is running better.

6 hours ago, Alexio Auditore said:

So what is this alternator rated for amps compared to the stock one?

 

Did you also have to change any other wiring  from the alternator besides what you mentioned above or is stock setup good enough to handle this one?

 

And what does a nation's alternator cost compared to the typical stock rebuilds?

 

I'm glad to hear your truck is running better.

The nations alternator states it supplies roughly 55 more amps than a stock alternator.  Pretty sure factory is 100 amps. The website states it’s a direct bolt in, however I chose to upgrade my battery cables and terminals to the military style. The alternator has a two year replacement warranty. It’s a very solid unit and you can use your stock serpentine belt as other alternators have a smaller drive wheel requiring a different belt, from what I have read. I am very happy with my purchase. However I am unsure which fix corrected my idle surge, regardless I hope it’s gone for good. 

 

https://www.nationsstarteralternator.com/180-Amp-HP-High-Output-Alternator-for-2000-Dodge-p/13874-180-hp.htm

My oe came rated at 136 amps. I think all the diesels all came with the 136, maybe not. But it was at the least an option.

Well, after putting 100+ miles on my truck today, the issue is not resolved and started acting up again. I pulled the codes and the only codes listed are below. At this point I’m stumped and not sure what my next steps are in diagnosing the issue. It did increase the idle under very light throttle however so it’s not just when the ecm is in control. Little scary if it was to last any longer than a split second. It is strange how my only gauge to zero out is the temp gauge. Thoughts? 

 

 

 

Could be ecm, if your old alternator was bad and took it out. Remember when not touching throttle ecm is in charge of idle, then it's apps. If still original get timbo.

17 minutes ago, Dieselfuture said:

Could be ecm, if your old alternator was bad and took it out. Remember when not touching throttle ecm is in charge of idle, then it's apps. If still original get timbo.

I thought at first it was only happening when idling and no pedal input. However, now it is happening when I am applying pedal input and this occurs while in drive and when in park. Is there a way to test to determine if apps is good/bad? Mine is still original. I did the reset where you key on and depress the pedal very slowly, however no change. 

To be honest original apps are junk, get a timbo and move on. If it doesn't help you're still a step ahead.

 

1 minute ago, Dieselfuture said:

To be honest original apps are junk, get a timbo and move on. If it doesn't help you're still a step ahead.

 

This was my initial thought of what the cause of the idle swings was caused by. I will give the Timbo APPS a go. I hope it isn’t my ECM, however I would think I would see more widespread issues if it was, but you never know. Thanks for the help. 

I ordered a new Timbo APPS this AM. Hopeful this will remedy my issues. I am ready to get a few tranny parts and some injectors and tuner, but new alternators and Timbo APPS must come first. Is there an accurate way to test my ECM to ensure it is working as it should? I haven’t seen any codes as others have seen when their ECM goes thankfully. 

This is probably a really stupid question , but can a bad coolant temp affect anything else with how the truck will run? 

I'm just thinking simple minded, but I know it can affect the way other vehicles can run if its bad, just not sure if it's the same with our cummins.

 

Genos garage has it for like 11 bucks. But the wiring should also be checked for any cuts too.

 

I did a quick search about the coolant sensor and a guy had symptoms similar to yours, rough idle, missing, so on. Ended up being the sensor, despite passing a voltage test too.

 

13 minutes ago, Alexio Auditore said:

This is probably a really stupid question , but can a bad coolant temp affect anything else with how the truck will run? 

I'm just thinking simple minded, but I know it can affect the way other vehicles can run if its bad, just not sure if it's the same with our cummins.

 

Genos garage has it for like 11 bucks. But the wiring should also be checked for any cuts too.

 

I did a quick search about the coolant sensor and a guy had symptoms similar to yours, rough idle, missing, so on. Ended up being the sensor, despite passing a voltage test too.

 

Thanks Alexio, I would be curious to know this as well? I have the high idle switch that plugs into the temp sensor, and that’s the only code that pulls. For $11 I wouldn’t see any harm in replacing it. I put a new t stat on mid winter. For now I am basically throwing parts at it, hoping one part eventually fixes this. 

I'd just hate to see someone throw a 1000 dollars into a rebuilt ecm and have that not be it. 

 

And does the high idle plug into the air intake sensor and not the coolant sensor? Or is it both?

 

Also, did you ever get an accurate read on your older alternator since it was spiking everywhich way with the voltmeter you were using? I do know that if it was bad to begin, the damage is done to the ECM and unhooking grids and changing alternators won't fix what's already damaged. 

 

1 hour ago, Alexio Auditore said:

I'd just hate to see someone throw a 1000 dollars into a rebuilt ecm and have that not be it. 

 

And does the high idle plug into the air intake sensor and not the coolant sensor? Or is it both?

 

Also, did you ever get an accurate read on your older alternator since it was spiking everywhich way with the voltmeter you were using? I do know that if it was bad to begin, the damage is done to the ECM and unhooking grids and changing alternators won't fix what's already damaged. 

 

Yeah, I really don’t want to throw a ton of money into parts until I know what the issue is. I just know my alternator was on its way out. I did not test my old alternator again. I put the new one on and off I went. I do still need to test the nations alternator  and see what readings I get. The high idle switch plugs into both the coolant temp sensor and the IAT sensor. I am hopeful there is a way to test the ecm, but most people who have had ecm issues show a code being thrown. 

Ya, usually it throws a whole bunch of codes to like everything else is wrong. Hopefully someone can tell us if a bad coolant sensor can cause problems like your seeing.

P

1 minute ago, Alexio Auditore said:

Ya, usually it throws a whole bunch of codes to like everything else is wrong. Hopefully someone can tell us if a bad coolant sensor can cause problems like your seeing.

I concur. Thanks for tagging along. I saw @pepsi71ocean stated that the below website is a verified and suggested ecm rebuilder and the website says $299 currently for a rebuild. 

https://autocomputerspecialist.com/shop-now?olsPage=products%2F1998-2002-dodge-ram-cummins-diesel-59ltr-i6-ecm-ecu-repair-service

Dont throw the towel in yet on the ECM. I have had crazy temp swings on my truck for 10 or so years, most swinging low. Pretty sure its in the wiring and most likely grounds you cant just clean. I lost my ECM about 8 years ago and had surging, more pronounced that what you are seeing and the temp would peg on a cold start sometimes and sometimes not. Never saw it drop like yours.

 I have however seen similar drops before and after the the ECM was replaced. The surging returned about 3.5 years ago and stayed with me for a while until one day messing with the MAP sensor and for some reason it stopped and has not done it since. That was 6 months or so ago.  

 I dont have the answer to the problem but I am willing to bet it has nothing to do with the ECM, and probably not you sensor either. I have 3 to prove it was not mine. At least I will not have to ever buy another.