Engine/Transmission (1998.5 - 2002) Engine surging questions

[HGDMARTN]

Hello again,

I am very concerned about my truck. It now has 119K miles and is out of warranty. Seems to have developed a surging problem. I have read the archives and am lead to believe that my injector pump may be crapping out and the cost of that scares the fool out of me. So, I want to lay all I know out and see what you experts think.

First noticed it about 1,000 miles ago as a slight hesitation that comes and goes as I drive steadily out of the neighborhood in 3rd gear at about 2K RPM. Appeared as a very slight surge, most noticeable just under 2000 RPM. I thought it may be water in fuel or just a tank of poor fuel. Drained water trap and have been through 2 tanks of fuel and it appears to be getting worse. It is still so slight that I doubt most people would notice it. It is most noticeable just under 2K RPM. Becomes less noticeable the farther away from 2K I get. Performs as it should at idle and at WOT. I have changed fuel filter. Fuel pressure using my mechanical gauge is 10. 5 at idle. Fuel pressure has been that way for 3-4 years since my first LP went bad. The surging is so slight that it feels almost as if my foot is feathering the pedal. Seems to be worse when truck is cold although it is still there at 190 degrees. Any ideas on what to check? I have not checked to see if I have any codes mainly because I forgot how.

Any ideas on what to check are much appreciated.



Thanks,

David in SC

 

[nps]

Any ideas on what to check? I have not checked to see if I have any codes mainly because I forgot how.

Check the codes. Turn the key on-off-on-off-then leave on and look in the odometer window. Post the results.

 

[PC12Driver]

I'm gonna vote for the APPS wearing out. Especially since your "surge" happens right about cruise rpm, where the contacts in the APPS will wear out first.



In neutral, slowly depress the throttle to the floor and watch/listen for flat spots in the rpm. Mine was smooth up to about 1600-1700, and then rpms would kind of hang in the 1800-1900 rpm range, and above that the response was linear again. If I depressed and released the pedal a bunch of times (engine off - probably about 30 cycles or so) my surging would go away for a little bit (like turning crackley volume knobs on a radio back and forth to clean the corrosion off the pot). That was only a temporary "fix", but it did point to the APPS being the cause of the problem.

 

[RBallard]

I just went through this, it is easier for the 6spd HO to determine APPS. I was able to determine it was APPS because when running cruise control, I had no problems. It only occurred when I was using the accelerator. I bought a replacement APPS and it is truly amazing how nice the truck runs now.

 

[tntframing]

The same thing happened to me. right around 2000 rpm it would surge and no power. it turned out to be an injection pump. its not hard to change. hpoe this helps



tim

 

[Vaughn MacKenzie]

I put up with considerable surging on my '01 HO and my '03 HO. Just figured it's one of the downsides of electronic diesel engines. I chalk it up to less-than desirable ECM programming, oversensitivity to signals from sensors, sensors that can be a bit out of whack but not bad enough to trip codes, etc.

 

[HGDMARTN]

I did the key trick and what I get is "P done". I assume this is no codes have been set?



You all have helped me already. Thanks and keep any info coming. I plan to dig deeper into the APPS theory.



Thanks,

David in SC

 

[GCULP]

DAVID, mine is doing exactly the same thing, there is another thread on here about this as well, that member changed everything from injectors, lift pump, fuel filter, apps sensor, till finally the injector pump. It appears to me that trying the apps first would be better considering the miles and the cost, it is probably ready to be changed anyway, and if that doesn't fix it, you have a spare apps. The only thing left after that appears to be the vp44. Good luck, keep us posted.

 

[HGDMARTN]

Thanks to the advice received, I am betting it is the APPS. I depressed the pedal many times like suggested and it seems to have cleared up temporarily.

That makes me rest alot easier as the APPS sounds like a great deal less money and time than the VP.

And, I need to get in there anyway. My cruise cable will not stay on the throtttle plate. I have put it on a dozen times and it will work for a little while. Then it pops off and no more cruise. Maybe a new APPS will fix that.



As always, thanks for the help.



David in SC

 

[Jeddi]

P0121 APPS Error

Hi All,



Been reading the thread on this APPS problem. I just had my 99 2500 checked a local dealer and they gave me error code P0121, saying it was some throttle sensor problem. Does that sound right? If it is, what does it take to replace it?



Thanks in adavnce..... Jeff

 

[GiesJ]

HGDMARTN - did you ever get this figured out? Was it the APPS?

Thanks,

Jason

 

[FourBarR]

121 and 122 are apps codes. replaced mine at 350000 kms. fixed the problem

 

[doldenburg]

I just replaced my apps,seemed to work good for first week now after a hiway run it will not drop down to low idle. runs 900 to 1100 rpm. will drop down to normal idle after shut down for a while. also does not want full rpm,will hesatate at 25-2800 rpm. Dealer said take to a diesel repair shop as he does not doe not do enuff with them. (at least he will admit it). only problem b4 I replaced it was check engine lite and slite stumble just off idle. any ideas? 2001 HO 6 speed, 220,000 mi. stock work truck. thanks

 

[dan_gilson]

I have the same problem. The truck is a few years older and has a few more miles on it.

I have a 98. 5. Does the odometer show the codes for that year?

Is there a good OBDII reader out there? I have one for the car but it does not seem to work for the truck.

What is the APPS? Where is it located. Can it be cleaned with some contact cleaner? Or is it better to have it replaced?

Thanks ... Dan

 

[JLandry]

I have a 98. 5. Does the odometer show the codes for that year?

Dan,



I don't believe so for that year.

Is there a good OBDII reader out there?

There are a lot of good code scanners out there. Go to your local auto parts store and see what they have to offer. If you buy one there and it doesn't work with your truck, you'll be able to return it.

What is the APPS?

Accelerator Pedal Position Sensor

Where is it located.

Front left side of the engine. In the diagram below you're looking at the left side of the engine. The APPS is identified... you can see a bell crank. On your truck this will be covered by a black plastic cover which can be removed.

Can it be cleaned with some contact cleaner? Or is it better to have it replaced?

It can't be repaired and must be replaced. If you buy an OEM version of the APPS, it comes with an entire bell crank assembly (quite wasteful) and is very expensive... in the neighborhood of $500 from Dodge and $377 from Hoesli Diesel. The actual throttle position sensor is a sealed black rheostat mounted on the back of the cast aluminum bell crank housing. It can't be seen until you remove the entire assembly from the engine.



An alternative to the expensive OEM version is to replace just the rheostat with one for about $100 from Williams Controls. See this thread for complete details (hint: you may want to start reading from the end and work back... it's a very long thread).



https://www.turbodieselregister.com...9611-anatomy-apps.html?highlight=anatomy+apps



Good luck,



John L.



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[blacksheepdiesel]

dan,

Find a buddy with the same truck setup (auto or stick) that does not have the same symptoms you do. Remove the APPS from his truck (leave it bolted to the aluminum bracket that bolts to the cylinder head) and install it in your truck - doesn't take but a few minutes. If your symptoms go away then purchase a new Williams APPS and be happy!!!

Godspeed,
Trent

 

[dan_gilson]

JLandry you rock! That was an awesome post. DC should hire you to clean up their service manuals! The information is much appreciated.

I played with the APPS and caused myself to get the dead pedal. I found another post and seemed to have fixed the dead pedal. I suspect that the APPS is on borrowed time. I will work on getting a replacement.

My APPS seems to have problems when cold. I will pick up from freeze spray from Frys tomorrow and see if problem comes back.

 

[GiesJ]

Dan -

Any decent auto parts store should have a code reader. Check your codes before you pull the trigger on an APP$. I thought I had the same problem and it turned out to be that my ECM was fried.

Good luck,

jason