Anyone ever done a high idle mod for the 5.4L in these trucks? Similar to what diesels do in cold weather

 

I did it on my last diesel but I've never heard of anyone doing it with the 5.4. I don't know why it would be needed because gas engines don't have issues with wet stacking and the gas engines heat up faster than diesels. My F-150 heats up at least 2x faster that my 08 F250 did.

 

its not necessarily for heat, but to keep the alternator running at peak RPM for a winch or extra lights. i had a high idle on my jeep that was linked to the cruise control, but that was a cable throttle body.

 

I'm interested myself. It's really too bad that there aren't upfitters for my F-150 to wire it up to, should I find the way to do it.

 

i know in my brothers dodge (cummins) when he is in park, he can press the on button on the cruise control and then raise or lower his idle with the accelerate or coast buttons in increments of 100RPM all the way up to 1500. his is an 07.5 so everything is controlled by the ECM.

i know its a completely different animal, but there has got to be something

 

you might want to check but i think the voltage at idle is the same as when reved up. and if not you can buy one that will handle all your electrical needs and not use a higer idle. plus it wont wast so much gas! just my $0.02

 

Blue is right, your voltage is strictly dependent on predicted battery temps. There is a "Z" curve in which the PCM sets the voltage based on calculated battery temp, no matter what engine speed there is.

 

im not really sure where voltage came into the conversation. the only reason you'd need to keep a alternator at a higher RPM as i described would be for amperage output. new alternator or not, no alternator is going to be able to keep up with the demands of a winch and having a second battery is just a really really gay bandaid. Warn's 12.5K winch at maximum load uses around 500-600amps. the goal is to be able to keep the alternator spinning where it makes most electricity so the battery replenishment is at its most efficient level. plus if im in a situation where i need a winch or excessive amounts of lights, fuel consumption is probably going to be last on my list

 

You can adjust idle somewhat with a tuner:



Being as there is no cable - this is not trivial to do in any other manner... other than a 'calibrated' brick on the pedal

MGD

 

There are a couple high rpm strategies used by the PCM. Cold Idle start up, low voltage, extended idle, AC performance, and alternator high field conditions. If you want to use the PCM to control, you need to trick one of these signals. AC head pressure would work, but would also would trip the high speed fans and suck 40+ amps.

Extended Idle, low voltage and alternator high field idle kicks are probably not high enough to be worth the trouble. Extended Idle simply raises idle rpm if idling for a length of time, most vehicles around 20 minutes. That is PCM internal timing, good luck on modifying that. Low Voltage is used by both the PCM and alternator for control and feedback. There are 3 - 4 power input lines into the PCM, trying to figure out which one the PCM uses to determine low voltage issues would be an interesting task. If a low voltage is determined, engine idle is raised but not to an unlimited amount. This will cause a "Check Charging System" DTC though if playing with the voltage values. But can be cleared pretty easily.

The PCM and alternator communicate in PWM signals. If the alternator tells the PCM it is in full field, the PCM will begin to raise the idle rpm after a set time if condition still exists. Making an interface to control this signal would be more work then simply adding a second alternator to the system.

All of these idle rpm increases are not that much, likely 850 rpm at the most, it depends on the particular engine calibration and likely differs between each engine option. The highest engine kick would come from cold idle conditions.

Cold Idle start works off the ambient sensor & ECT, but playing with this affects engine timing and performance. No biggie during idle only, clearing DTC's would be easy. But would need to interface the two sensors. Other than that, I don't know of any other way to increase idle rpm except one.

If you want my honest opinion. Have somebody press on the gas pedal...

 

its looking like the brick method is the only really feasible way of going about it.

 

Now I see where you're going with this. That makes sense now! I think it would be nice to be able to keep some accessories going without killing the battery. I only had one set of offroad lights on my F250 so they didn't draw much. I mostly did it for cold weather to keep the motor warm.

 

As MGD stated you can change the idle with a handheld tuner. Im almost positive there was an option to adjust the idle on my Edge CS tuner. Im not sure how high you can adjust it though. I know from the factory they have it set extra low to save fuel while idling.

 

If you could find the wire and value the gas pedal sensor is sending the PCM you could modify that signal. It was built in my 05 F250 I just soldered two wires together to use the BCP idle which was a 1200rpm base and monitored battery charge. It makes the A/C kick a lot harder down here in Texas. My A/C barely trickles cold at idle...

 

the main thing i was wondering is if there was some way to tap into the cruise control system, basically make it work even though the vehicle is sitting still