Surging and Bucking after Truck warms up
 

Help needed!
Last week my truck started loosing throttle on the way home from work about 30 minute drive. About 5 minutes from home, I didn't think I was going to make it, I had almost completely lost control of the throttle, it had a mind of it's own. (go back to a week before) water pump broke, water got it fan and all over everything in motor) just so you all know. My buddy brought over a scanner and although it didn't have any codes it did throw some while it was running and started the problem. Po123 and P1286, APPS TPS, so I replaced it. Didn't fix it, read up on the forums and saw something about IAT and ECT, replaced both, didn't fix it. Weird thing about this is that is runs great until it warms up, then slowly starts and gets undriveable within 30 - 45 minutes, I'm thinking maybe the ECM is going out, but I'm not sure, is it heating up before it acts up. maybe something got wet and corroded, but I've cleaned all the grounds and replaced 3 sensors. I'm completely stumped, any help would be appreciated.
Thanks.

You know of course you have the infamous failure prone VP44 injection pump...go to Bluechip diesels website and perform the diagnostic check list.

Ummmmmmmmm - Larry? As the TOP aren't you suppose to be impartial, unbiased, non-judgmental, yadda, yadda, yadda? Us over valved 24V guys have got feelings too ya know. I mean sheesh! it's bad enough that we have to bear the albatross burden of the VP44 - ya don't have to rub it in, do ya?

Cheers!

Mike

The scariest thing about scary Larry Top is he is brutally honest. The VPs are great when they work, but when they don't prepare for a LOT of troubleshooting. I'm still fighting with mine.

I'm on my 3rd one.

Third one in how long?

Sorry Mike... I don't mean to hurt your feelings I just figure you guys deserve honest answers with out a lot of sugar coatings confusing the issue.

Where are you getting them from? you do know that ALL VP44s are not the same?... There are a lot of rebuilds out there I wouldn't use as a boat anchor let alone put under my hood.

You REALLY need to go with a Reputable source like Bluechip or Scheid if you do not want to roll the dice.

LOL, Going thru something very similar with a local kid............ except a 48RE built by a "Expert"

2nd time in 3 months, "builder" says kid beat on it ( now why in the HECK would someone "build" a trans and expect granny to drive it?) ".........

Anyway, fast forward about 5 grand, kid is finally listening to my original pitch, "Call Dave Goerend and DON'T BS him about your intended purpose, and buy what he says"

Want to bet it doesn't puke this time?

been about 4 years but I think it was bluechip, I made sure to get a good one with new electronics, but, whats wierd is that when the pump went out before, it went out, it didn't have to warm up, I'm also getting random sensor codes like they are getting too much voltage, I checked the alternator and it seems to be putting out a solid signal so the voltage irregulartity isn't coming from there.

From blue chips site:

"DEAD PEDAL, OR INTERMITTENT
LOSS OF POWER

This is THE MOST COMMON DRIVABILITY COMPLAINT and is an intermittent one that happens most often when the truck is hot or working harder, but can occur when cold too. My experience tells me that 4 times out of 5, Dead Pedal is worse hot, but 1 time in 5 it is worse cold! The symptom of Dead Pedal is rarely caused by the APPS (Accelerator Pedal Position aka Throttle Position Sensor) and 90% of the time it is caused by a faulty computer on the top of VP44 Injection Pump. These numbers are NOT an exaggeration. Computer failures are due to the “Lead Free” solder connections on the circuit board in the computer becoming crystalline over time, which causes an intermittent electrical connection and intermittent Dead Pedal symptoms. Its use is mandated by the Federal Government!

Another two causes for Dead Pedal have shown up recently. One is when the 12 volt supply to the injection pump proves to be intermittent, which can be checked by connecting a test wire to pin 7 ( Red wire with a light green tracer in a Dodge ) in the harness at the plug of the injection pump, and extending it up to the dash, where you can monitor the voltage while driving, either with a test light or volt meter WHEN THE ENGINE IS DOING ITS DEAD PEDAL THING. The loss of power at pin 7 can be caused by no primary voltage getting to the fuel system relay in the PDC ( AKA fuse box under the hood) from the brown wire with a white tracer coming from the ECM, a loose socket for the fuel system relay, a bad relay with pitted contacts, and even a bad connection in a connector on the firewall in the engine harness. Sorry this one isn't simple, or easy or fun to do, but it has happened enough times by now to make it important to be included here. If the brown wire with a white tracer coming from the ECM doesn't have power then the fuel system relay can't be turned on, and you have to diagnose the ECM as described later in this diagnostic page.

The other cause of Dead Pedal is contaminated fuel. The resulting rust and corrosion make internal parts bind, stick, not fit properly, etcetera. Customers don't want to hear this, especially if it involves a pending WARRANTY claim which will surely be denied. Usually when the pump gets corroded or rusted to the point it causes Dead Pedal everything mechanical in the vp44 pump is junk, and a replacement pump is the cheapest and only cure. We can dismantle your pump and determine if contamination is a problem, if needed for your diagnostic purposes.

There are no codes that specifically diagnose Dead Pedal or that will condemn the computer and therefore the VP44. This is an instance where a lack of codes is most important, and where you have to prove that the only other component that could cause this symptom, the APPS, IS or IS NOT the cause of Dead Pedal.

The lazy inaccurate way to diagnose the APPS or TPS as the cause of this drivability issue is to scan or read the ECM (not the PCM) to check for any codes pertaining to the APPS, such as a 121 or 122. Codes 121 and 122 only indicate that the voltage going in or coming out of the sensor was outside of the desired parameters, at least once, since the codes were last cleared. Therefore these codes do NOT tell you what happens to the signal when they ARE within appropriate parameters, which is what really matters. If you DO have either or both of these codes you MAY OR MAY NOT need an APPS. To diagnose the APPS accurately you need to use an oscilloscope or an ANALOG voltmeter, one with a needle, to measure and monitor the signal voltage on the blue wire with a black tracer, on a Dodge, in the APPS electrical harness plug. A scan tool or a digital voltmeter has too much averaging or buffering of the signal to be useful for this test. First verify the appropriate voltage range and voltage apply rate with the engine off. Turn the ignition key to the “on” position and slowly press on the throttle and slowly release it. You should see voltages from about .6 volt to 3.5 volts, and not ever see a jump in voltage, or the needle bounce. It should go up and down smoothly, directly related to throttle movement. If it repeatedly or intermittently jumps up or down, then replace the APPS. The adjustment of low voltage at idle, or “resetting” or “recalibrating” the APPS is NOT as important as some people want you to think, and does NOT cause Dead Pedal. The ECM learns the range when you do the install of the APPS correctly and does NOT cause any drivability issue in my experience.

As this sensor can be very intermittent, I strongly suggest you ALSO do the same test when driving the truck to prove the APPS is or isn’t the cause of your Dead Pedal OR DRIVABILITY issue. Extend the signal wire used in the previous test up to the dash of the truck, hooked to the analog voltmeter, and drive it until Dead Pedal or naughty thing happens and look at the voltage on your voltmeter. If you are holding the pedal still and the voltage drops when the engine drops power, or the needle quivers at the same frequency as the stutter, skip, or miss, you need an APPS. If the voltage stays the same and the power drops, you need an Injection Pump!"

Almost sounds like it is the VP-44 computer, not the ECM, but the procedure to diagnose is there.

. . Several years ago after doing some work in the injector pump my truck would not hold steady speeds. . Would surge and slow down. . I got a TPS code so I replaced it (those things are not cheap). . Still had the problem. . Even went so far as to replace the injector pump from another truck that was running great. . Still had the problem. . After talking with a bunch of people someone asked if I had "programed" the TPS after I had disconnected it. . Never heard of that. . He said turn the key on but do not start the engine. . Slowly push the throttle pedal all the way down and then back up. .
. . Embarrassed to say, that took care of the problem. . I now have a good used spare TPS in my tool box. .

It was the ecm, oh well.
No ecm codes, but it was the ecm.