Over the last 3 weeks, I've had an issue with my truck accelerating by it self. Not WOT like other posters experience but more like going from let's say 15% throttle position to 25%. At normal cruising speeds 35 or 60 on the free way it will happen a few times then stop. 

 

Other times I'll be going through a parking lot trying to find a spot and my truck will keep its rpms at 1500-1800 and I have to hold the breaks or shut off the truck and restart. 

 

I tried a apps reset eventhough I have timbos tps. 

 

Tried leaving the batteries disconnected for 24 hours.

 

Tried running Lucas for injectors. 

 

Tried a known working tps(another persons truck with no reported issues tps)

 

I have a new vp44 from thoroughbred with 6k on it.  Timbos with about 28k. 

 

7 x.0010 injectors  about 35k

 

Any ideas?  My next thing I'm going to check is vacuum leaks.

I have experienced this some myself. The first time was with an ECM failure. Probably not your issue since you can still drive it. The second time it turned out to be, at least ad far as I could tell, a bad splice in the 5v signal wire for the sensors. That is where I would start. Even another failing sensor on the that circuit can cause crazy s**t to happen. How to pin it down, I dont know. Have you checked for codes? 

 

The vacuum has nothing to with fueling, at least on my 02. It only controls some mechanical things like HVAC, CAD, cruise control.

No codes. Checked with blue driver and smarty. When I was viewing data live the throttle percentage would stay the same no spikes while driving, but of course it won't do it when I watching data live.

 

As far as signs wire, do you mean the one to the tps? 

Then we are a bit different. My scan gauge showed the spikes. And every so often when it surged it would pop an APPS code then go dead pedal for a minute or so. After that it would run fine for a day or 6 tiil it would happen again.

 

The ECM sends a 5v signal to all of the sensors. A short or bad sensor or in my case a bad splice caused me heart ache. The engine wiring diagrams in the articles section show it better than I can explain. I am an electrical midget compared to some aroud here.

Ah I see. I don't have the dead pedal issue either. I still have full throttle response when I push the pedal. But, even tapping the pedal a bunch doesn't drop the rpms I have to shut it off for it to stop. It's very strange... I would think a code would show but nothing... 

 

I turned offf and returned the programming to stock on my chips and still no luck. 

 

Do you think it really is electrical and not mechanical ie sticking injectors?

I know the smarty you return to stock programming, to take the Comp out of the equation you have to disconnect it from the MAP and data link. I also uplug the pump tap wire.

 

The fuel and throttle control is all electronic. A sticky injector will miss fire or perform badly. 

 

When mine would do it I always had full throrrle response. I could overcome it just by sticking my foot in it, unless it went dead pedal then I had wait for the throttle to come back. Also with the tps codes I was getting I figured it must be the TPS so I replaced it with a cheap one off of ebay. It stopped the surging so I bought another Timbo. Put it on and surging was back. WTF, so I reinstalled the cheap one and the surging went away but then I had a constant p222 code. I'd clear it it would come back imediately. So ai put the original Timbo back in and fought on and off for the next year or 2. Since repairing the splice mine has worked fine and still have the original Timbo on the truck. 

 

The splice I speak is not factory, it was self inflicted. It is possible that your signal wire is chafed some where, or a sensor that is going south just hard to say with out any codes. Chasing these types of gremlins are not fun especially with no codes. 

 

If youmcan leave your live data tool connected and drive it around until it does act up and least you see if the computer is surging the engine. I know mine was. Hopefully one ofmthe other electrical genius's can add something to this. @Mopar1973Man, @Me78569???

You need to watch live data while it is happening.  

 

Guessing either apps or map sensor is causing fits

  On 6/24/2019 at 12:00 PM, Me78569 said:

You need to watch live data while it is happening.  

 

Guessing either apps or map sensor is causing fits

 

Yup.

 

TPS will either jump to 100% or drop to 0% and toss a error code. 

 

MAP sensor you need to look for sudden changes in values or possibly lack of change like stuck value.

Update, when viewing live data I found that my Actual throttle position is set at 12.5 which should be 0. And when it revs up, I do see it on my scanner. 

 

Does that mean the timbo is shot?  It didn't last long if it is.

I'm going to turn a different direction. 

 

1. Pull the alternator and have it bench tested for AC ripple, replace if needed
2. Do the W-T ground wire mod. This will stop majority of the AC noise in the system.
3. Do the Field Wire Fuse Mod (optional) just to protect the PCM. 

Random throttling could be caused by AC noise infecting the tach signal from the cam / crank sensor. This will create random pu down swings of throttle while in cruise or manually controlling the throttle. 

 

After about a year I finally figured out this problem... so if any of you have this same issue hears what it is.  This is a recall 799 requiring a reflash of the ecm. Here is the info...

 

1998 Model Year Ram (BR/BE) trucks equipped with a 5.9L Cummins 24 valve diesel engine ("6" in the 8th VIN position) built at the:

 

The engine control module (ECM) on 30,000 of the listed vehicles may cause the engine speed to increase unexpectedly if an erroneous crank position sensor signal is received. To correct this condition, the ECM software must be updated (reflashed)

 

 

NHTSA CAMPAIGN NUMBER: 98V209000

CHRYSLER/HIGH ENGINE IDLE SPEED

THIS CREATES A SIGNAL WHICH IS MISINTERPRETED BY THE ENGINE CONTROL SOFTWARE, CAUSING A HIGH IDLE SPEED CONDITION.

NHTSA Campaign Number: 98V209000

Manufacturer CHRYSLER CORPORATION

Components ENGINE AND ENGINE COOLING

Potential Number of Units Affected 30,747

 

Double check the AC noise too. This can do this on all 98.5 to 2002. Mine did before doing the W-T ground mod.