Hi All,

Hopefully the group can help me diagnose this. A little over a month ago I was idling at a light and my RPM surged to about 1000 from its normal 700. This only lasted a second or two, but it was noticeable. Nothing after that so I didn't give it much thought. Fast forward to last Monday, going to work in the morning after the Ex had sat for about 12 days. Just going down one of the side roads here, basically idling along at about 45 mph, and that same kind of surge hit...un-commanded acceleration that lasted a second or two. It wasn't violent or a launch, but it was very noticeable. This happened 6-8 times in the next five miles and then nothing for the rest of my 15 mile trip to work. Nothing again until yesterday. At the advice of @Sous and @SkySkiJason I downloaded Forscan to my tablet and attempted to log some data. My tablet got disconnected from the OBDII during much of my trip yesterday, but today I got the whole trip home logged, with a few stumbles included.

Problem is I have no idea what to look at, or what it all means. What PID's should I be looking at, and what do I do to graph it up like some of these other threads? Any ideas what could be causing this? I'm a bit worried as the wife has our other vehicle out of state for the next year and the Excursion is my only transportation.

I've already checked ICP, new just over a year ago, and the harness over the driver's valve cover. Both good as far as I can tell.

Thanks!

 

@BWST seems like a FORScan charting wizard. What’s your advice for PIDs good sir?

 

Because I decided to take a trip for the past week, the instructions and video for the new and improved PID Charting Tool are not done.

That said, you can upload your file here and either BWST or I can chart it for you.

As for PID's, we like to see RPM, VSS, ICP, IPRDC, FUELPW, MFDES, and whatever else you think might be pertinent to your issue.

We have some default PID's that will automatically be charted, but some of those will not help you right now. They are more for general knowledge.

 

^^^that'll do it. Sorry you are having problems, Eric - these intermittent issues are a pain to track down. Maybe we can catch it in the act, by starting Forscan and logging every trip you take with it for a bit. I use Forscan Lite because I think it's easier to use, once you've picked your PIDs.

You said you already logged a trip? What PIDs did you pick for that trip? Did you save the log?

 

Is your fuel bowl heater unplugged?
Mine went bad and would surge and it didn't blow the pcm fuse but would cause connection issues with the obdi too.

 

Hi Wes. Yep, bowl heater has been unplugged since I rebuilt it a few years ago.

 

My log is attached. I chose the PID's that @Sous and @BWST had listed in their new charting tool thread:

• ICP = Injector Control Pressure
• RPM = Revolutions Per Minute
• IPR = Injector Pressure Regulator
• VSS = Vehicle Speed Sensor (MPH)
• FUELPW = Fuel Injector Pulse Width
• EBP = Exhaust Back Pressure
• MAP = Manifold Air Pressure
• MFDES = Mass Fuel Desired
• EOT = Engine Oil Temperature
• IAT = Intake Air Temperature
• MAT = Manifold Air Temperature
• MGP = Manifold Gauge Pressure (Boost)
• TFT = Transmission Fluid Temperature
• VPWR = Vehicle Power (battery voltage)
• TC_SLIPACT = Torque Converter Slip

Except I substituted in

• APP = Accelerator Pedal Position

for ECT, as 4R100 7.3's don't have Engine Coolant Temperature. These "surges" were uncommanded, I wanted to make sure the pedal position sensor wasn't going haywire.

Hope this helps! This is 30+ minutes of log time. There were a few stumbles during this trip, so hopefully we can "catch it in the act"! The stumbles this time were pretty minor so I may have to help point them out if necessary. Otherwise, maybe we can tell if the system is healthy or not and have a place to start.

 

@ArmyLifer , I will have to check if there's a PID for it but you should include the IVS (Idle Validation Switch) in your monitoring. @Dan V is trying to figure out something similar also.

 

I'll be watching...mine is rather subtle though.

 

I am pretty sure there is an IVS PID...

Working the data log now, be back soon. I am not as good with them as BWST, but I usually manage.

 

First, you should change the data log output to export as a .csv format as indicated in the PDF attached. I have manipulated the data on the log you uploaded above, but for future reference and to make things easier on you, the other format is easier to use.

EDIT: Deselect PID "EBP" and use "EBP_A". For some reason EBP is an erratic reading, but EBP_A is smooth and what it should be.

EDIT again: I believe there are two EOT PID's, you want to use the second one on the list, is that right @BWST ?

 

I’ll look for IVS and include it if it’s there.

Mine is quite subtle too. 90% of the time it’s at idle or low speed. I’m guessing that at higher speeds it is less obvious.

Driving in today was smooth as glass for the first 25 minutes. “Nothing to see here”. Unfortunately Forscan Lite lost communication at about 23 minutes. Naturally the Ex had a rather long surge 2 minutes later as I was coming into the gate checkpoint. Probably 8-10 seconds worth.



Anyone have a clue what this “ELM” is? It is the same error I’ve had every time I’ve lost communication.

 

I have attached the data log instead of taking screenshots of it due to the length and not really knowing where the surge occurred. I didn't really see anything out of the ordinary, except for the EOT, which may have been the wrong EOT PID on the list to log.

 

ELM is in relation to the scan tool you are using I believe. I am reviewing the chart now looking for anomalies in the other PID's at idle/zero VSS.

 

Sous, thanks for the charting help. I'll get the jacked up PID's fixed and add IVS.

One spot on the graph that is one of the little surges is at 801 seconds. At a stop, but idle RPM goes from the normal 625-650 up to close to 900. Another possible one is at 1048 secs, where the idle speed goes way up before I leave the light.