Surging

[jlwelding]

A month ago I started having surging and idling problems. I checked all the usual, fuel filters, pressure and everything in check. At hwy speed you can feel it surging in fact at all speeds of course at over 2500 rpm not so much. If you set the cruise control it goes away. I can watch my throttle on my adrenaline and its fluctuating up and down when using accelerator. At idle at a stop it will go as low as 500 rpm and Ive watched it climb as high as 1800 rpm. The apps was about a year old so I thought that had to be it.Put a new one in and roll along here for a bout 100 plus miles and the new apps starts doing the same thing again. No codes except the grid heaters which ive disconnected. If I turn off my addrenaline on my phone is that good enough or do I need to disconnect under the hood to test if thats the problem? With out codes its a crap shoot. I talked to Dap just because all my parts, fueling is from them. Airing it out with them we both are leaning towards ECM or connection. Timbo has not gotten back to me after leaving a message. What is the name of the guy in Florida who works on ecm's?

[Tractorman]

Interesting that the surging goes away while using cruise control.  With manual transmission trucks, the ECM controls throttle while using cruise control - the APPS is completely out of the loop.  It seems like you are getting an unwanted signal through the APPS when driving without using cruise control. 

 

I think  you need to physically disconnect the Adrenaline completely and then test drive.  If possible, use a scanner to observe the APPS signal with the engine running and while driving the truck.  With the engine at idle, the APPS signal should be 0 percent.  This is controlled by the idle validation switch in the APPS.

 

I recall someone having a similar problem and it turned out to be that the throttle low limit set screw was loose and the APPS couldn't set the idle validation switch.

 

- John

Edited February 27 by Tractorman

[jlwelding]

Is there anything in the WT mod that would have any effect?

[Tractorman]

Since the W-T wiring mod essentially shortens and improves electrical grounds for the ECM and PCM and alternator, I would think it would be less likely for electrical interference to be a source of your problem. 

 

Not sure if you have done the mod and also not sure if your question was referenced to after the W-T wiring mod, or before the mod.

 

- John

[jlwelding]

Sorry about that, yeah already done. I follow ya, it should just make it even more bullet proof.

 

[Tractorman]

10 hours ago, jlwelding said:

I can watch my throttle on my adrenaline and its fluctuating up and down when using accelerator. At idle at a stop it will go as low as 500 rpm and Ive watched it climb as high as 1800 rpm.

 

I use an OBDLink LX OBD2 Bluetooth Scanner through my Android phone to read live APPS signal data with the engine running.  Do you have this capability?  It would be good to verify that there is a 0 percent APPS signal commanded when the engine is at idle. 

 

What exactly do you mean when you say, "I can watch my throttle on my adrenaline and its fluctuating up and down when using accelerator."?  Are you talking about the per cent of throttle commanded?  A steady throttle should result in a steady per cent value for the commanded APPS signal. 

 

- John

 

 

[jlwelding]

I think I have the same OBD2 ive mostly retrieved codes, I'll check on that. And yes the throttle percent, when its acting up I can brace my foot against the firewall and get a good steady and you can watch it climb up and down on its own by as much as 7 to 10 percent. But I can set the cruise control and it is good.

[Tractorman]

1 hour ago, jlwelding said:

And yes the throttle percent, when its acting up I can brace my foot against the firewall and get a good steady and you can watch it climb up and down on its own by as much as 7 to 10 percent

 

How about when the engine is at idle.  Does the APPS stay at zero percent when the engine rpm's vary?

 

- John

[jlwelding]

I didnt have my phone on when it did the idle thing so I dont know.