Ashton Taylor

Hello,
Before I start just want to say I’m very much a beginner when it comes to swaps (this is my first) so I’d appreciate all the help I can get. I recently ls swapped my 2011 crown Vic with a 5.3ls from an 02 Tahoe and have an ar5 trans from a Colorado behind it. Engine is completely stock besides a sheet metal intake, 102mm TB, and cold air intake. I completely rebuilt the motor from the block up and it currently fires up and runs, but not well. The problem is idling, it sits around 1200 and doesn’t settle down once it’s warm, it just stays there. I have a stand-alone harness so all the emissions stuff is gone along with secondary o2s and the ecu is from an automatic. The trans connector and VSS are not plugged into anything at the moment so I’m guessing that’s the issue. I’m not planning on running a VSS, but I’m wondering if I need to do something with the trans connector to trick the ecu into thinking it’s in neutral. I’ve tried looking at forums but I haven’t found a clear answer on how to wire the trans connector. I’ll also mention that I’ve tried messing with the tune in hptuners. I’ve tried swapping the trans to a manual and non electric auto but there was no change in idle so I’m guessing it’s somthing with the trans connector or perhaps with the intake setup. The tune is completely stock besides disabling the vats. Let me know if you guys have any ideas on what to do. The cars been sitting for months at this point and I’m at a loss for what to do. Any help is appreciated, thanks.

nleming

I noticed your PCV system is wide open. There are several diagrams on google to get that sorted out. I would check your fuel trims to see if you are dealing with a vacuum leak.

Ashton Taylor

I’ll look into that, appreciate it

TrendSetter

Take that intake off and inspect that is indeed in your trash can and nowhere else.

now install a stock truck intake throttle body and injectors.

Also the stock ar5 vss is compatible with the stock ecu you are using (0411/p01) so it wouldn’t make sense to not use it.

TrendSetter

Also you need to cap that 90 degree elbow on the passenger side of the throttle body. It’s a giant vacuum leak. Put your finger over it while it’s running and it should idle down to almost normal

bobcratch

is your engine coolant temp sensor working? if that is unplugged or broken it will cause a high idle as the ECU thinks it is always -40C.

but, it does sound like you have a vacuum leak

Pocket

iTrader: (22)

Sounds like you need to adjust the TB blade to get the IAC within range. Watch the IAC value with a scanner

The open PVC port on the TB is pre-TB clean air intended to go to the PS valve cover. There should be no vacuum from that port. Leaving it open allows a little unfiltered air in, but won't hurt anything during the troubleshooting phase he's in
You can see the actual PCV port on the DR valve cover just has a filter. That gets connected to one of the NPT ports on the bottom of the intake. Forgetting to plug one of those ports will cause a high idle though
As he has it, the PCV system is just and engine bay oiler. It doesn't effect the idle since it's not connected to the intake at all

VSS, P/Neutral and CTS will not cause a steady high idle

If that intake is super cheap or very old, it may not have the cyl head flanges machined properly. The small head bolt flanges actually protrude above the cyl head flange and if the intake isn't machined to clear them, it will not seal to the heads. Most recent sheetmetal intakes have addressed this. After you fix the idle issue, you'll need to fix the IAC whine that all aftermarket TBs have