Been nailing down some idle issues that are tied to the compressor cycling and I think I have them solved but have one other behavior and wondering if its normal?
The truck is drive by wire and whenever the ac compressor engages my fuel trims stay normal (0 to -1) but throttle position goes from 5% to 9-10% for idle. To me this is indicative of the truck wanting more idle air...what table do I need to look at to get the throttle position back to 5% or is this normal?

Edit: Forgot to mention, RPM's stay normal and I'm using HP Tuners.

 

DBW modulates the throttle plate angle rather than using an IAC. So yes, seeing an increase in TPS is normal. I don't know the location, but there are tables in HPTuners that allow you to set target RPM or airflow with AC engaged/disengaged.

 

engine>idle>rpm> base idle rpm

 

The a.c compressor simplu loading the engine, not an iussue.

peace
Hog

 

Yea like stated, its completely normal. Throttle blade has to open in order to let the extra air it needs in. You need to be looking at idle air trims to tune the AC tables. If your idle air trims increase/decrease dramatically when the compressor engages, you need to add/subtract from the AC air tables.

 

Okay, so the idle issue I thought I had nailed down reared its ugly head again today...just posted this over on the HP boards as well:

My truck keeps setting P0103 when running the A/C and I can't seem to nail down whats causing it and have not been able to log the issue. What I notice is that from a cold start if I have the A/C going about 5 to 10 seconds after starting I'll get a severe idle dip and then about 2 to 5 minutes into driving it sets the DTC. If I wait to turn the air on until I'm already into my drive it will run all day without setting the DTC. I'm starting to suspect that when the 2nd fan kicks in is when the dip happens. Anyone run into this before or have any idea whats going on? I'd love to log it and know the why and how behind it but I have no idea what cfg I need or what to be looking for...

Edit: Okay so I figured out the idle dip and its nothing the tune can fix. I'm running 14" SPAL e-fans along with an underdrive pulley on the stock alternator and alternator pulley. Inrush current from the fans is whats causing the initial idle swing thats setting the code. Added some AC offset and cut back on correction times and that seems to have helped...we shall see.

 

no experience with the underdrive pulley set up personaly but from everything i have found out about them says that at idle your barily having any output from the alternator.. i would say the reason you have no problem once your going down the road is that you have enough rpms to get the alternator spinning and making enough juice to keep the fans a/c and everything else going.. if your voltage is to low for to long while running the truck is gonna think something is wrong and set a code.. same basic principal as if your running your truck without a thermastat and it sets a code because it didnt warm up fast enough

 

^^^ Yessir, exactly. For now I've set P0103 to no error reported but I think I'll just bump my AC idle rpm a bit and see how that does...sometimes the obvious escapes me.