2006 E450 low speed idle

Most likely is that you are asking demands of your engine to fulfill. The load on the engine to provide those loads does not seem to make the computers speed up the engine.

If, at idle, say your engine develops 5HP, able to keep itself rotating. Then you add air conditioning, now you need 6.5HP, so speed up please. Are the batteries down.. charge them.. 7HP. But the computer seems to want to slow, and not give more gas to match the load.

When I have A/C on and arrive at a stop light, I have to shut off A/C to keep up the RPM's so the clutch doesn't try to creep ahead and just lays calm.

Sounds like the Idle Air Control (IAC) is finally acting up.
If that's what it is it will get worse and even die when you stop.

A couple possibilities- one is the throttle bodies sometimes gum up and pass less air, resulting in slow idle.

The other is the Idle Air Control Valve may be sticking or electrically defective. This valve is supposed to compensate for various idle loads such as AC compressor. It is controlled by powertrain control module.

No IAC valve on the E450.
Idle is controlled by the electronic throttle body plate.

Unhook the battery for 10min to reset the vehicle adaptive strategies.

Throttle body most likely needs to be cleaned. There is no IAC valve and the PCM will adjust to whatever load is appied, up so something like 40 Hp at idle.

Home Skillet wrote:

Unhook the battery for 10min to reset the vehicle adaptive strategies.

If you do this, you may need to do an Idle circuit reset.
After starting, let run/idle without touching anything for 15 min. While the ECM sorts it out. Then turn on the AC and let Idle for another 10 mins.

If you take off and drive right after it may run worse than now Until the ECM re learns the Circuits.

Sounds like the throttle body. Remove the air tube going from air cleaner to throttle body, purchase some carburetor cleaner, spray and manipulate throttle valve with engine off, wipe off any residue

that may come loose. start engine and let idle spray short spurts into throttle body and it should be good to go.

Daughters Suburban needs this once a year. Low idle and turning on AC almost kills engine. Fuel additives work. I had two K-5 Blazers with throttle bodies and never had a gum up problem. one had

175K miles the other 285K I used either marvel mystery oil or gum out in the fuel occasionally. Daughter says she doesn't need it, she only needs pops, his spray and his 15 minutes of time.