aceman28

Hello, im new to these forums but would really appreciate some help if possible. i have a 2001 dodge ram turbo diesel with 260,000 miles. and for the last couple months when driving the truck the rpms will surge from like 2000 to 2500 rpm maybe even more and will sometimes stay that hight for minutes at a time. and it went away for almost a week after recharging the AC but its back and worse than ever. dont even want to drive the truck its so bad. I noticed when i turn the ac on the rpms surge and when i shut it off it stops, but it will also do it while no ac is on also. Does anyone know what the hell is causing this?? i hooked up my code reader and it doesnt throw out any codes. only thing i replaced so far is the fuel filter thinking that might fix the problem, but no luck. It almost feels like its sucking air or something or kicking in and out of over drive but even without the overdrive on it still does it. please someone help me im going crazy here!!! thanks in advance for any advice.

j-fox

Go into your profile and fill out the signature, so we know what year and info of your truck.

If it is an auto ( I bet it is), the torque converter may be unlocking and re-locking.
Mostly caused by dirty grounds. Clean battery posts and check block grounds of the big cables.

Welcome.

aceman28

thanks man i will definitely check all the cables and grounds. the cables on the battery are clean, but maybe there is another connection thats bad. saw someone post somewhere that it could be electrical noise from the alternator. and they said to wrap the negative cable with aluminum foil.

Tallguy67

Aceman28,
Check out this thread. Your symptoms sound like what I was dealing with and it turned out to be a problem with the APPS. My options were bad VP, unlocking TC or APPS. The symptoms seemed to point to the APPS most of all so I started there, an APPS reset made the truck happy again.

https://www.dieseltruckresource.com/...40#post3114540

aceman28

Thanks for the info, I really don't know anything when it comes to cars, for example what's APPS?? And how do you reset it?? But also I have the torque converter lock up switch inside the truck and just for the Hell of it I flipped it on today when driving home and the problem disappears completely, so my question is since that fixes the surging when I flip the switch what does that mean?? And what would be the most likely fix?? Thanks for all the help I'm pretty clueless when it comes to fixing cars.

Tallguy67

I will answer your first questions first before we get to the rest - just for teaching sake between us chickens. The APPS is the Accelerator Pedal Position Sensor. It is the same as a TPS (Throttle Position Sensor) in a gas engine. To calibrate it, disconnect both negative battery cables for a few hours. You need to discharge the capacitors and there are different opinions about how long it takes. To be safe, I just leave them disconnected overnight. In the morning, I reconnect the cables and hop in the truck. Turn the ignition switch to run (don't start truck) and slowly push accelerator to the floor and back. By slowly, I don't mean 5 minutes slowly but I took about 15 or 20 seconds to get pedal to the floor and then release at the same rate. I then turned the ignition switch to the off position. Let it sit for a few seconds and fired it up. For me - Bob's your uncle, surging problem solved. At some point I am going to need a new APP and I will get one from Timbo (dude on this board) as they last longer than dealer or parts store APPS.
Given that the TC lockup switch solves your problems, you quite likely have found your problem BUT I will defer to the opinions of one of the tranny gurus.

BTW - no need to apologize for being a noob. I was there a little over a year ago. I have tried to be polite and ask questions and the folks here have taught me a lot. Some grumpy, pushy or arrogant folks didn't get much help and don't hang around here much any more.

aceman28

TallGuy67 thank you so much for explaining what APPS is, i disconnected my negative battery cables just now will let it sit overnight and reconnect and do as you explained to see if that fixes it. Is there a for sure way to find out if i need a new APPS?? i hope this fixes my problem, i mean if flipping the Torque Converter loc up switch inside the truck makes the problem go away, then i assume its not the transmission cause wouldnt it do it regardless of flipping the switch? But in any event i am greatly appreciative of all your helpful information, like i said i have owned this truck since 2005 but havent had really any problems at all except replacing the starter 4 times, but up until about 2 months ago before this started only other repair was replacing the AC system, but i live in Palm Springs, CA were it gets as hot as 120 in the summertime. i will post tomorrow after my drive of about 100 miles. thanks again!!!!

aceman28

oh yeah and as far as replacing the APPS how much does something like that cost, and is it something easy to change, and where the hell is it located on the truck??? LOL told you i was clueless on anything to do with Automotive, i can build a house from the ground up but cant figure out how to fix my truck go figure!!!

aceman28

Well, update on rpms surging while driving. Did as you said to do Tallguy67 and disconnected batteries overnight and reconnected this morning then pushed down excellerator slowly and back up then turned truck off and back on and worked perfectly. Truck doesn't surge at all anymore!!!! Thank you so much man you saved me a lot of money taking to mechanic. We will see how long it lasts.

Tallguy67

Ace,
You just put a big grin on my face. The folks on this board have been so helpful to me over the last couple of years that is nice to finally be able to pay it back to someone. When you APPS goes and you have to buy a Timbo, I seem to remember they are a few hundred bucks.

It is on the front, driver side of the engine just above the VP44 (injector pump). The VP is where all the lines that go to the injectors originate. Follow the accelerator cable from the firewall. It will end in the APPS. I haven't replaced mine but it sounds like a moderately easy job.

aceman28

Tallguy yeah you have been more help than you know. I will know how to fix this problem next time now until I can buy another one hopefully it will last for a while before having to do that again. Runs like a brand new truck again. Thanks a lot man really appreciate the help.

Jen Tiemann

I want to thank you two gentleman for this thread. We were having this same problem, followed the steps, that were so clearly explained, to reset the APPS sensor. Truck is running smooth as day. We now know we'll have to replace the sensor. THANK YOU!

Lary Ellis (Top)

Glad you found what you needed That is why the forum exist, sharing information for each others benefit.

BrokeMomRacing

I bought a 99 2500 24 valve about 3 months ago. Previous owner, said “the surging happens about every 6 months or so, clean the terminals and it will be fine”. One month ago the VP went out, replaced the VP44 injection pump. Not a performance one just the one from auto zone. (It was the only one in town and i didn’t have time to order one). Since the surging is constant. I’ve been told the turbo is surging. After reading several situations on here i believe the APPS needs to be replaced.

my question is, is there something else it can be? Is there a order series of thing to be replaced or will not function properly after replacing the injection pump?

thank you