The Diesel Stop banner

1 - 9 of 9 Posts

·
Registered
Joined
·
123 Posts
Discussion Starter #1
HOW CAN I CHANGE MY IDLE R.P.M.S., WOULD LIKE TO INCREASE IT APPROX. 50 TO 75 R.P.M.S. TO SOOTH OUT ENGINE?
 

·
Super Moderator
Joined
·
18,870 Posts
The idle RPM is controlled by the powertrain control module (PCM), which is the computer that controls the engine and automagic tranny.

Your normal low idle RPM is 680 RPM with auto tranny or 650 RPM with stick shifter. But in cold weather, after a minute or so, the engine will idle at a higher RPM, depending on how cold it is. Click here for some discussion on the cold ambient pkg (CAP).

So the only way to change your idle RPM is to change the computer program in your PCM.

One way to do that is to install the Ford auxiliary powertrain control module (APCM), which is the brains behind the Ford auxiliary idle controller kit (AIC). However, that APCM defaults to 1,200 RPM as the lowest pre-set idle RPM. You can manually set the idle RPM anywhere between 670 and 1,200, but it takes some fiddling with the APCM every time you want to set the idle RPM at less than 1,200.

The only other way is to have a computer programming guru go into your PCM and change the program in the PCM. That's do-able by someone like Jody at www.dp-tuner.com . If you prefer your low-idle RPM to be, for example, 750 RPM instead of 680, then Jody can do that.

Of course, if it's cold enough for the CAP to take over, then your idle RPM will probably be higher than whatever low idle RPM you choose.
 

·
Super Moderator
Joined
·
25,209 Posts
Probably a better approach would be to find out why it doesn't idle smoothly and fix that. /ubbthreads/images/graemlins/shrug.gif
 

·
Registered
Joined
·
360 Posts
I would like to add a sketch I drew up that I believe represents everything being described in the instructions for most of the DIY AIC's. I only want to add it for anyone out there like me that feels like they need a little more of a visual of how & where the wires need to be cut and attached to the relays & the switch...
If ANYONE sees something wrong with the schematics / photos I post here please feel free to copy & paste into whatever photo edit program you have & make the changes.
I want to point out that I have NOT installed this AIC to my vehicle. And my biggest concern is that I don't have the correct value pots. AND that I am terrified to do this that I might fry my PCM! BUT having read so many posts of guys saying they HAVE messed around with the return signals to the PCM by doing this modification, I think my worries might be excessive. Please , ANYONE that sees something wrong post or edit the sketches to help others out.
There is some language in the TPS explanation that with regards to the pot. values OR how they should be wired that is probably wrong. MY vehicle is a 2003 E-350 & I have not found a chart that lists the oHms values to expected RPM results that say it (the chart) represents specifically that model year (2003 or earlier) . The chart I found IIRC was for a 2006 MY and I don't even recall what engine. This post is just to add some Schematics for others that might be like me & want/need a little bit more to understand what & why all this wire rerouting is about & does. Take a look & tell me what's wrong or right about my Schematics.
 

Attachments

·
Registered
Joined
·
360 Posts
Thanks coffeeeh20:
If the rotational direction is the only thing wrong with the drawing, I would be pretty pleased with that. You must have a good eye for detail to spot something like that! Any ideas if the pot. values are correct to accomplish the desired IDLE SET points & then the variable RPM (throughout the rotation) of the 2nd larger pot? Have you seen any wire schematics that would verify color codes to the TPS for a 2003 E-350 to make certain to identify the 5 volt INPUT vs. the variable OUTPUT? As I understand it the center TERMINAL is always going to be the wiper of the pot. But center WIRE out of a wire harness is no guarantee that it's the center "terminal" from the pot. Any thoughts? I guess a meter would verify any possibility that Ford decided to switch things up in the actual wiring harness parts.
I'm trying to get this file I got on Ohm's vs. RPM expected to attach to this thread....
 

·
Registered
Joined
·
360 Posts
Attempt to attach file
Ohms Values for AIC .png
 

·
Registered
Joined
·
360 Posts
Not sure if these values are correct for 2003 E-Series.
Don't understand .....If 1200 RPM is both 43K & open circuit, What Ohms values controls RPM's lower than 1200? The chart shows the 600 RPM value (presumably Idle), So it seems strange that it doesn't show values above 43K to represent the RPM values between 1200 down to 600. Maybe it's just assumed that 1200 RPM is the minimum value one would want to start at when they engage the AIC? But I would think there must be values above the 43K listed to account for 1200 to 600 RPM? Anyone tell me if I am misreading this chart?
 
1 - 9 of 9 Posts
Top