Engine/Transmission (1998.5 - 2002) High Idle

[garylmoore]

I changed both fuel filters yesterday, made a 45 mile drive and shut it off. Nothing else was touched.
I started the truck today and the idle immediately went up to 1000. I made a short drive and by the time I got it home, it was running about 1200 rpm in park.
Any ideas for me?
Thanks. Gary
2001 Ram 4x4 Fass Titanium Lift Pump

 

[Dl5treez]

Check the throttle linkage/cable for something bent or interfering.

 

[Ozymandias]

Also check the resting voltage of your batteries, very low voltage can raise the idle.

 

[garylmoore]

That's pretty interesting. The truck has sat a while without being driven.

 

[garylmoore]

Ok. High idle persists, idling anywhere from 1200 to 1500 RPM. I had a charger on the batteries for 4 hrs, then drove the truck 90 miles, ammeter shows 14+ amps, high idle is still there. I am in the process of moving so my meter is 370 MI away. I'm going to borrow one tomorrow and check to see what the alternator is putting out.
One odd thing is that every time you start the truck the ammeter in the truck shows about 11 volts. Put it in gear and charge goes to 14.
slipping belt possibly?
This couldn't have anything to do with the rear wheel (abs?) Speed sensor? My abs/brake trouble light has been lit for a while now.
I will check alternator output and post tomorrow.
I have a 700 mile drive Monday and the vehicle is undrivable at this point.

 

[Topzide]

Amps and volts are two different animals. I'm sure that you're mean 11 volts on the volt gauge. If it was 11 amps, you'd be going backward if the grid heater is on. Voltage issues will create many issues. Charging the batteries without being able to check the voltage doesn't give you any answers. Need to check voltage before charging, then charge them up of course checking the batteries without the cross over cable attached. If you have a helper or can have meter where you can see it, check voltage drop when starting truck. If original alternator, could be one part and batteries the second. Hope you can borrow what you need to check the truck. Good luck.

 

[garylmoore]

No. Sorry, not amps, volts. I thought I had corrected that.
I've been driving U-Hauls across state moving for the last 5 weeks. The truck had not been driven. New Interstate batteries were installed Last Summer. The truck was operating properly when it was parked.
In an earlier post, I was told the high idle was probably a low battery voltage and both my meters were in another state. I put 90 miles on on the truck to see if that would help.
It did not, which is why I reposted.
Yes I understand that I'm not going through the proper troubleshooting manner, but I live alone, my friends are working and I have just started trying to diagnose the problem.
So. Idle is about 1100 cold, 1500 warm and in gear. When I start up I'm always showing about 11 volts, and increase in throttle always brings a past 14 volts. I have no belt noise whenever I increased throttle. I've inspected the belt and although it's somewhat worn, it's not cracked or damaged. I may replace it anyway.
I'll see if I can get my hands today on a meter and maybe someone to help me check it.
The alternator is not original. I put a Nations alternator on it about 4 years ago to stop the cycling in the torque converter, which worked.

 

[Ozymandias]

Low Voltage showen on the dash gauge can also indicate a broken temperature sensor under the driver side battery. It is a built in diagnostic feature of the Gen3 trucks.

Use a multimeter to see if the voltage measured at the battery with the engine running is as low as the dash gauge says. If it is the temp sensor the real voltage will be in the + 13V range whereas the dash shows low.

 

[Ozymandias]

Sorry, my bad, this is the Gen2 forums. I don't know if the above feature applies to that generation trucks.

 

[garylmoore]

The alternator is bad. I am showing 13 volts at the battery while idling at 1500 rpm. I also had the torque converter cycle a couple times on the way home from buying the new belt. That had not happened once since the original Nations alternator was installed.
The Nations alternator was installed 2019 and out of warranty. I ordered a new one from Nations and ETA is tuesday.
Advance Auto had a New Bosch, but it wasn't going to be in until Tuesday, and it was only $15 cheaper than the Nations.
All New Napa alternators were made by a company I had not heard of so I declined.

 

[garylmoore]

Low Voltage showen on the dash gauge can also indicate a broken temperature sensor under the driver side battery. It is a built in diagnostic feature of the Gen3 trucks.

Use a multimeter to see if the voltage measured at the battery with the engine running is as low as the dash gauge says. If it is the temp sensor the real voltage will be in the + 13V range whereas the dash shows low.

Well that sensor is definitely there. I replaced it whenever I first bought the truck. But I am showing 13 volts at the battery, and I'm showing 14 at the dash after I give it a little gas and 11 at startup. I can't tell you if the 11 volts was real or not, but the 14 at the ammeter never happened.
Even when I bring the RPM up past 1500 on the truck, the voltage at the battery terminal never changed. It stayed at 13.1 volts.

 

[Topzide]

Wow they are a pricey unit! I know when the time comes for alternator or a starter, I'll have them rebuilt locally. Cheaper and better then most of what is available. The shop near me has been around 20+ years and has already rebuilt some items for me and others that I know and longest it took was 2 days! Little hole in the wall type shop with great people! like not having fitment issues since it's the same case that came off with new insides. JM2C on it. Glad you were able to get it figured out!

 

[GAmes]

Well that sensor is definitely there.

I've had two of them fail over the years. The first one replicated a failed alternator and the second one allowed over voltage spikes. I could control the over voltage with my grid heaters until I got home since they are on a toggle switch. The FSM has a resistance range for checking it. Lots less expensive than a new alternator.

 

[garylmoore]

Wow they are a pricey unit! I know when the time comes for alternator or a starter, I'll have them rebuilt locally. Cheaper and better then most of what is available. The shop near me has been around 20+ years and has already rebuilt some items for me and others that I know and longest it took was 2 days! Little hole in the wall type shop with great people! like not having fitment issues since it's the same case that came off with new insides. JM2C on it. Glad you were able to get it figured out!

Well the reason I bought them was because that brand Alternator was reported to stop the cycling of the torque converter. It worked also. I had not had the torque converter cycle once since 2019.
I had tried everything else suggested in the forums and that was the first thing that actually stopped it.

 

[garylmoore]

I bought the current batteries in the truck January of 2023. They were the best available from Interstate for the Diesel Ram.
I take them both to Interstate this morning. The Electrolyte test showed both batteries had a full charge.
Then both batteries failed the load test.
The guy said the best he could get out of the batteries was 13.1 volts and according to the electrolyte test, he should have gotten at least 13.6 or 13.8.
He replaced both batteries.

How often do two 10 month old batteries fail at once?
I'm going to pull the alternator and have it bench tested.
Could the battery sensor have something to do with this situation?
Very weird.
Thanks

 

[GAmes]

The temp sensor is easy to check with a multimeter. The only hard part is accessing the connector.

 

[BigPapa]

I'd also check your crossover cable.

 

[garylmoore]

I'd also check your crossover cable.

The one that goes across the top of the radiator? I hope that is not an issue, all the cables were replaced new 3 years ago. But I also did not expect 2 bad batteries in less than a year.
So how would I check Big Papa? Am I checking resistance end to end? Any idea what a good reading would be?
Thanks... Gary

 

[Ozymandias]

Nope, you need to load test it.
Means measure voltage drop right to left while cranking.

Resistance means nothing as a single strand would give you a good reading.

 

[Topzide]

Bad batteries seem to be everywhere nowadays! Not limited to any one brand either. Used to be the big names were the ones to go with, doesn't seem to hold water today. I got a set of Champions that were on sale at Pep Boys in the beginning of 2019. Still hold up and on battery tender when not driven for more then 24hrs or more. I still have the simple electrolyte tester that gives me another wat to check things. Glad you're getting some answers.