Had this issue once before for a split second but truck jumped back to having power. Tonight though no luck.Was driving home and RPMs were stuck at 2000rpm and 20mph.

 

If i pushed the pedal all the way down still same rpms just held at 2k. Truck is an 01 auto and p0720 is the only code to show. Fuel pressure is good. Truck drives great tell I get to 20mph lol. 

Edited February 15, 20196 yr by 2001white

This may help.

 

 

Might want to test for alternator noise. Then also consider doing the W-T ground wire mod.

 

I am planning on buying a new sensor and getting that in tomorrow.  i looked for AC current but didnt seem to get any noise. I might just need to take it in some place. Are any of the main parts stores able to test for AC noise? 

21 minutes ago, 2001white said:

i looked for AC current but didnt seem to get any noise.

 

All charging systems have a small amount of AC noise. We need to know how much because 10mV AC to about 30mV AC is normal. Above 50mV AC the random issues start. Then above 100mV AC the problems get worse. Please report what AC voltage you measured. 

 

23 minutes ago, 2001white said:

I might just need to take it in some place. Are any of the main parts stores able to test for AC noise? 

 

You'll have to call around to find a place that does AC ripple testing and willing to report a voltage value. Remember this is a FULL LOAD value where our test is idle state test. 

Think I have the settings right now. Showing .57 did see it hit .10 for a bit then to .30-.40 then jumps to .50s then back lower.  no lights or anything on that could cause extra noise. 

I would pull that alternator and have it bench tested to verify that its failed for sure. Then it would be time to look towards an alternator replacement. 

 

I would disconnect the field lead on the back and go for a test drive and see if the problem goes away. If not you might be looking at having that ECM verified being it might already be damaged from the AC noise. 

hmm so the problem goes away after a while like today truck drove fine no issues. then maybe tomorrow things will go south so maybe that at would fit why i am reading inconsistant readings?

Edited February 16, 20196 yr by 2001white

Get that alternator tested if it fails replace it. 

On 2/15/2019 at 5:12 PM, 2001white said:

Think I have the settings right now. Showing .57 did see it hit .10 for a bit then to .30-.40 then jumps to .50s then back lower.  no lights or anything on that could cause extra noise. 

You need to do it after you drive it so grid heaters aren't cycling, or unhook them from battery. Even if truck is warm they will still be cycling,  so best way is to drive it above 25mph I believe and come back without shutting the truck off, turn all accessories of and try it again. Then you can try turning electrical things on and see how high you can get it to come up. If you rev motor up it should also go up some. Write it all down then report your findings. Also do WT ground mod if you haven't yet.  

Edited February 21, 20196 yr by JAG1

alright couldnt find a place to test the alternator. So i bought a new one along with a speed sensor still same issue no luck.  With the new alternator i was able to get above 20mph but it just jumps back and forth I did get a video below. 

 

I reset the apps as well during alt install. 

 

Edited February 17, 20196 yr by 2001white

I did some testing and drove the truck yesterday about 300miles to tow my car. didnt have much of a choice. Truck ran awesome at highway speed and most in town was okay.

 

I found that my issue seems to be always shortly after start up and at low speed. If I can get past the shutter after few miles things are fine. Also dosent matter if engine is cold at start up or hot. As long as the truck stays running it wont have any issues after the inital surging. no codes im thinking maybe apps? 

On 2/15/2019 at 7:12 PM, 2001white said:

Think I have the settings right now. Showing .57 did see it hit .10 for a bit then to .30-.40 then jumps to .50s then back lower.  no lights or anything on that could cause extra noise. 

 

That's not 57 millivolts, or 0.57 volts. That's 0.57 millivolts! That alternator is likely fine!

0.57vac is too much imo, I had issues with high 0.4s I'm below 0.2 now but each truck reacts different. Say you have other weak grounds that I don't, that may contribute to issues also. So I think the lower the better and now that we can have it below 0.2vac with WT ground mod, we should aim towards that number. 

This is why I suggested verifying with a bench test to make sure that its not just a "Cheap DVM" that can't measure odd frequencies. 

On ‎2‎/‎15‎/‎2019 at 7:01 AM, Mopar1973Man said:

All charging systems have a small amount of AC noise. We need to know how much because 10mV AC to about 30mV AC is normal. Above 50mV AC the random issues start. Then above 100mV AC the problems get worse.

 

To rephrase what @Mopar1973Man is saying:   10 mv AC, 30 mv AC, 50 mv AC, and 100 mv AC would be saying the same thing as  .010 v AC, .030 v AC, .050 v AC, and .100 v AC respectively.  So, if @2001white's meter is showing .57 mv, that would be the same as .00057 v AC.  That seems a bit off the scale to me, but I may not be reading his meter correctly.

 

- John

 

If this isn't confusing enough, let me know so that I can make it more confusing.

Even stock setup with a fresh alternator would be in the 0.030 AC volt range or 30mv AC volts. To be 0.57mV AC I don't think is possible. This could be because its a low grade DVM and not capable of measure varying AC frequency.  

its possible that my DVM is low quality. sadly couldnt find any local place that can do a bench test. Thus why I went to napa and bought a new alternator. Maybe this new one is also bad my DVM seemed to read about the same so im about to throw the DVM out of the equation. Im not sure what the odds of 2 bad alternators are. Timbo did say on their site that bad apps can cause issues like what im having and show no codes.  Guess i will know once USPS drops things off. 

 

I plan to do the W-T ground set up but at the moment its to been mostly 3deg outside where I live so hoping to do that this summer once I can solve the issue. 

Most all NAPA stores have an alternator bench tester. 

6 hours ago, Dieselfuture said:

0.57vac is too much imo

 

Agreed. But his meter doesn't show 0.57 volts, it shows 0.57 mv, or .00057 volts.

 

Low quality meter or not, it's on the mV scale. Will likely be more accurate than a meter that's sitting on the 20v scale or similar. Regardless, telling him to pull the alternator based on that reading was bad advice.

 

@2001white I'm a little late to this, but if you want an easy way to test the alternator's contribution to this problem, disconnect the main alternator fuse and go for a drive.

 

Hopefully your new apps solves your problems. 

 

Here is the test from the factory on the new alt thats getting similar reading from my DVM.  Should have apps in this weekend from the looks on the tracking.  I wish my napa could run a good test but they told me all they can do is pass or fail test and the autozone and o'reillys were the same pass fail and of course the old alt passed those tests fine. 

Edited February 21, 20196 yr by 2001white