Shortly after getting my new (to me) 05 back in April, my idle will on occasion, see-saw when I put the clutch in or am in neutral.

Normally, it idles just fine... but let's say I'm slowing for a stop... I could be empty or towing, doesn't matter. I push the clutch in, and RPMs will drop to idle, then will rise up 300-400 RPM, then drop back to normal, then repeat. This will happen probably 4-5 times before it usually settles down. Sometimes it doesn't settle down before I start moving again.

Any ideas what this might be? Truck is 100% stock, no power or engine mods at all. Air filter is clean... it's an Amsoil drop-in. Exhaust is stock. Only "mods" are a fifth wheel hitch and Airbags.

Rob

 

Mine does this as well, I was told b4 that it was the tst causing it, didn't do it stock, or I didn't notice it. I'm sure it is normal and just the ecm increasing rpms for a certain parameter or something.

 

Could be several things. Could be a sticking FCA, apps sensor, map sensor...........any codes?

 

My shows no codes, although I do get the occasional 336 from the tst, once every couple months. 05's do not have apps. Mine usually does coming to a stop in neutral, idle fluctuates from like 600-850 a couple times and then stops, not all the time though.

 

You still have an APPS. Your APPS is mounted inside the cab if it isn't on the engine. There are 2 idle validation circuits in it as well, either one could be causing a problem. As for code # 336......thats a crank position sensor code. Wouldn't be caused by a TST. Now 236 , I could see that! That would be an overboost code. I get that from time to time as well with the quad race box. Never sets the check engine lamp, just shows up on a code check. What guages do you have if any? A rail pressure guage could help diagnosing a stuck ( or sticking) FCA.

 

My 05 does it too, since new, with no engine mods. Seems to only happen when I'm coming to a quick stop on the interstate.

 

My auto does same thing in gear when i come to a stop after a long steady run. Like when coming off the highway. it does with or with or with out the edge. I has a stumble feel to the idle, it doesnt vary the RPM 300, but it will stumble for about 1 second, and repeats 2-3 times then clears up.

No codes, fuel pressure stays the same when it does it. (rail and LP). I have a RocTech CPS advancining the timming.

 

It's normal. Mine will do it when engaging the clutch while the truck is still in motion.

MikeyB