Fellas, I know this most likely has been talked about and maybe way way back I even started a conversation on it, but my surging is back and i'm looking for thoughts. All summer my truck seemed to work fine with no surging, now that the weather is getting colder , i'm starting to feel it alot. Today it's about 4-5 degrees out and when driving along trying to hold a consistant speed I feel it surging up and down. If I use cruise control it maintains speed with no surging. I'm running 16-19 psi for fuel pressure always , no codes showing in the odometer. I remember last time I had issues I did a reset on the apps, even adjusted the voltage on it, took the IAT sensor out and cleaned it .I think I remember somewhere reading if it doesn't surge with cruise it's not likely the Apps Whatever I did back then it seemed to eventually go away, maybe the weather was warming up, can't remember. Anyway, I was thinking today, i wonder if possibly the IAT sensor is getting weak or bad and now that the colder weather is here it,s not registering accurate and fueling wrong

Remember I'm not using a IAT sensor... Mine is locked to 143*F (2.2K Ohm resistor)So I tend to think the APPS sensor is more the cause... Any error codes?

I too have a surging problem. Sometimes it is pretty bad, sometimes it is almost non-existent. I was talking to a friend of mine that has had several CTD's, and one of his had a similar problem. He said that he took it into the dealership as it was still under warranty and the dealership said it had something to do with the turbo. He was not sure exactly what it was since it was warranty work, but he thought it was something to do with the oil line or passages? I thought mine was due to the PCM as it seems to have happened shortly after I swapped out my auto for a manual trans, but after putting in a PCM and an ECM from a 99 manual truck it still does it. I will have to do some more research to try and find why it is doing it, it does it both with or with out the cruise control on. Hope this helps a little, maybe at least give you something else to look at???

Am thinking it has to do with your apps sensor .

Now my truck started to do this and my check engine light came on and tach quit. But it left a crank sensor code, I havent fixed it yet it just happened but the thing I dont't understand is when the tach quits I have my attitude monitor to check rpms and it reads the right rpms so dont they use the same sensor or what dose the attitude use to monitor rpms?

My surging was like thisDriving along without OD on ..... rpm would jump 200rpm ...... just a few seconds .....APPS reset with battery disconnect fixed for meCant remember if it happened in OD as well - pretty sure it did