2013 4.3L MPI idles at 940

[505callyourball]

With two different IACs the idle has stayed the same. Vacuum lines look good (one large behind tb that runs to PCV and a small that Ts). The small runs to the fuel rail I think and the other hose of the T disappears behind the engine somewhere. I sprayed starting fluid all around with no change except an RPM drop if I sprayed it at the IAC muffler. Engine cover says 625 rpm in neutral. The dash tach and inductive tach read the same thing also (940). I've also disconnected the throttle cable with no change. I haven't noticed any issue on the water. I hope I'm missing something simple. Thanks in advance for the help guys.

 

[achris]

The TPS may be out of adjustment. This will cause the ecu to add fuel,and open the IAC up a bit. You need to get a laptop with the diagnostics on to see what values the various sensors are reporting.

Chris. ...

 

[505callyourball]

Is that a dealer-only procedure? If the value is wrong would the next step be replacement? Doesn’t seem to have an adjustment. Thank you

 

[achris]

The actual software is quite expensive. That said, I have it, and it's definitely paid for itself.

yes the TPS is adjustable, but you need a multimeter or the software to do it...

Chris. ...

 

[tpenfield]

I had a very minute air leak on the plenum of my 7.4 MPI engine. It cased about a 300 increase in the idle RPM. Maybe, check around the air intake, throttle plates, intake manifold, etc. again for any sources of a leak.

 

[alldodge]

T disappears behind the engine somewhere.

The hose goes down to the fuel pump regulator which is on the port side of the motor behind the motor mount. Remove the vacuum line off the regulator and see if you have vacuum.

 

[505callyourball]

The hose goes down to the fuel pump regulator which is on the port side of the motor behind the motor mount. Remove the vacuum line off the regulator and see if you have vacuum.

Speaking of that, whatever is down there is quite loud. It comes on with the key and continues while running. I assumed it was something with the fuel injection. It’s a rather loud, irregular buzz/hum. Runs great though.

 

[alldodge]

There would normally be a hum from the pump, but it being loud might have an issue. Check your fuel pressure at the rail

 

[505callyourball]

Update:
The inductive tach did match the dash tach but I think they’re both wrong. The inductive is wildly inaccurate as rpm increases so I can’t trust it (tried all settings). The dash tach can change with its cylinder# screw so no way it’s 100% on either. Most importantly the engine sounds like it’s at idle and goes into gear nicely. Reads about 800 now on dash and that’s maybe 5mm from where it should be. Thanks for the help