An easy way to temporarily step up idle speed for increased rate of charging.

[Doctor W]

I'm trying to think of an easy to effect way (pushing a button???) to temporarily increasing the idle speed on a 97 4.0 Jeep engine with the 136 Amp alternator........to lessen the amount of running time at idle when charging the battery or to increase available power when using a winch.

I thought of a button that would increase idle speed using the the A/C idle -up system.......on old cars they used to have an idle speed solenoid, but these Jeeps (4.0 I6 in ZJs, XJs and TJs) don't use that sort of system.

Any suggestions or ideas????......has anybody done this before??????

All advice and suggestions are welcomed, thanks!

 

[JIMBO]

:sombrero: Too bad you don't have a JK/JKU--

The AEV Procal Module (AEVPM), has a setting for controlling "idle" when atta rest-

I don't know if they have an AEVPM for TJs-

Good luck

:costumed-smiley-007:wings: JIMBO

 

[reece146]

Short pin 12 on the PCM (XJ). This raises the idle speed to 1200 RPM IIRC.

Search NAXJA for details and specifics in case I am mis-remembering the details.

 

[Lynn]

Your Limited has electric seats, right?

Just cut a stick long that reaches from the front of the seat to the pedal. Move the seat forward to increase rpm, back to decrease...

Seriously, I knew a guy that owned an old Caddy, and used such a stick for cruise control. Not recommended.

 

[Token]

Hand Throttle.. TearFlex makes one that's about $40..

 

[Hill Bill E.]

Short pin 12 on the PCM (XJ). This raises the idle speed to 1200 RPM IIRC.

Search NAXJA for details and specifics in case I am mis-remembering the details.

This. Search for the user name 'TAZ' on Jeep forum (possibly on NAXJA also) he did a write up on this mod.

I used an old 'dash pot' (solenoid) like they had on the old carberated cars with auto trannys, and modified it to fit my CJ's carb.

Flip of a switch, and the dash pot held my idle at 1300 RPM's. It was manually adjustable at the solenoid (rod screwed in/out) so i could set the idle anywhere between 1100 and 1500 RPM's

Looking to do this mod with my TJ also, just haven't researched it yet.

 

[jeep-N-montero]

Hand Throttle.. TearFlex makes one that's about $40..

You beat me to it, a hand throttle works great.

 

[Doctor W]

Thanks fellas....obviously a few different ways to skin this cat!......I'll research on NAXJA for the Pin #12 and a simple button.

I've got a hand throttle on my Landy and use it for running up the idle speed.......and other uses.......problem with the Jeep is it's already got 3 cables affixed to throttle lever ( gas pedal, auto tranny and cruise control) so a bit crowded.

I love the "stick and power seat fix" .......I've actually done this to lock on brakes when I had to undo the big (32mm???) nut on front axle stub shaft when changing the Rzeppa CV joint in a front wheel all by myself one time.

 

[Doctor W]

1200 RPM IIRC.

.

What does "IIRC" stand for......I've seen it before but have never known what it means.

Thanks!

 

[reece146]

IIRC - if I recall correctly...

The pin 12 mod is something that is in the XJ PCM for fleet/service vehicles like forest service or police vehicles. The idea being to raise the idle when required for running equipment. I'm not certain if the ZJ version of the PCM supports this - AFAIK ZJs were never sold in fleet service so maybe it wasn't incorporated.

Supposedly there is a guy in CA (?) that can reflash the XJ PCM for performance mods and as part of that can raise the idle triggered by pin 12 as well.

My white XJ has the pin 12 mod. Works simply enough.

 

[DaveInDenver]

Just cut a stick long that reaches from the front of the seat to the pedal. Move the seat forward to increase rpm, back to decrease.

Another option is a shower rod or window curtain rod. If you don't have infinitely adjustable seats this allows you to adjust the length on the fly to change your cruise control set point. They are also spring loaded, which makes it easier to install, and not as rigid in the case of emergency.

 

[1stDeuce]

The XJ PCM ('95-01) will support pin 12, but ONLY on auto-equipped XJ's. (It requires the vehicle be in Park/Neutral before it will work.) It also cancels if you put your foot on the brake, which is less than ideal for winching. It controls to 1100 rpm, which allows the alternator to put out over 90% of it's rated amperage.

I am running a modified TJ manual trans PCM cal for '97-99 that uses the AC input to trigger high idle to 1100 rpms, but if you have an A/C equipped jeep, you can't really use it without some rewiring of the A/C system and some stumbling when A/C cycles. It doesn't care about gear, brake, or anything else, and just runs the engine at 1100 rpm when the PCM gets told that A/C is on. Inquire by PM if this might work... I'll share.

If you have an auto trans TJ, you should be able to run the XJ auto trans ECM to get pin 12 to work. That will also give you a control circuit for an electric fan, but you may need to put a resistor across that circuit to to mimic the relay and keep the CEL off if you don't end up running a fan. But again, it has the drawback of needing to be in park or N, and brake apply will kill it. '00 and older TJ should interchange with '96-00 XJ.

The simplest option really is a hand throttle, which can be pretty cheap. Even with 3 cables, you should be able to find some place to hook it in. I would suggest making it so it only works for low throttle settings. That way it'll be easier to fine tune, and you won't be tempted to use it for cruise, or snag it with a shirt sleeve and run the engine to WOT while you're reaching for your dropped cell phone at a red light.

Of course, the coolest option is an electronic control, like this one:
http://www.offroadengineering.com/product-offroad-jeep.html
Someone else used to sell a likely cheaper version of this, but I don't see it anymore. (Was it howell??)

Hmm, you could probably also try to mimic the temperature sensor at -40F. That might result in an idle speed closer to 1000rpm?? It would probably toss a CEL when you switched it though.

I'm out of other tricks.
Chris

 

[K2ZJ]

I have thought about installing a throttle control from a lawn mower to mine. You can route it through the firewall and attach it to the throttle body. But like yours I have 3 things on there now so there isn't that much room.