Extended Idle 97-01 Install

[badron]

so kicking up the idle speed is critical.
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I want to get it to work on my stick. With my deep gearing I can idle over most things. But it's so SLOW and to touch the gas almost always starts the wheels spining. The Eidle will give me a little extra speed without over doing it.

 

[Begster]

so kicking up the idle speed is critical.
============================
I want to get it to work on my stick. With my deep gearing I can idle over most things. But it's so SLOW and to touch the gas almost always starts the wheels spining. The Eidle will give me a little extra speed without over doing it.

Hand throttle.

A bunch of the guys in my old club who had sticks had hand throttles.


fyrfytr1717: thanks a lot. I somehow managed to reverse the orange and black wires. I will say that while attempting to put the wires to the correct configuration, there is a certain configuration that will turn the dash lights on when you hit the ext. idle switch. Everything works now.

 

[fyrfytr1717]

Sweet, glad to hear it's working now! The Orange and Black are easy to switch because they are mirror images of each other on the Fog and Idle switches. Throw in the fact that you're most likely using a pigtail other than the one intended for the switch and it gets even more confusing.

 

[Begster]

Yep, that was why I think I reversed them, because I pulled them out of the fog pigtail. The stupid part was I actually had the factory pigtail for the idle switch, and some amount of wire too, but I believe I jumped the gun and pulled the wires out before I made note of which ones went where.

 

[badron]

Hand throttle.

A bunch of the guys in my old club who had sticks had hand throttles.
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So simple an answer. I must becoming a gismo geek to over look it. That way I can have any RPM/speed I want! Thanks again.

 

[ReverendOD]

Yeah without the option to manually set the idle speed thats is an awesome option. Getting around the NSS may not be a big deal but bypassing the 0mph might be?

 

[jeepcomj]

any way I can make my '98 4.0 5 speed do this?


I didn't have a wire in pin 12, but I just converted the xj from auto '97 to manual '98 wiring and everything, so I pulled the wire and pin from it.

What else do I have to do to emulate the park/neutral circuit?

-Pat

 

[Ewen91]

i too have a 98 cherokee 5-speed original harness, but i have upgraded the harness with a pin and wire comming from the pin 12. I ground it but nothing happens. what else is needed to make it work on a 5-speed?

 

[jeepcomj]

alot is needed, apparently.

the ecu doesn't use that pin. I even bypassed the clutch safety in hopes that the ECU would think it's in neutral.

but, when I put the automatic ECU in with the bypass, it worked...but threw check engine codes because there is no transmission.

 

[kastein]

I haven't verified that this will work, but you can try installing an auto ECU for your year and wiring in an auto TCU for a 97 (must be a 97), then installing 270-1000 ohm 1 watt power resistors on each solenoid drive wire to ground.

You may need to add a significant amount of wiring to a stock manual XJ to get the TCU in there, however. Probably not worth the effort. I would install a hand throttle instead.

Was the extended idle ever available factory on standards? I would think not, because there is the distinct possibility of the vehicle running away, or someone stealing it, neither of which is something the police really like.

 

[casm]

alot is needed, apparently.

the ecu doesn't use that pin. I even bypassed the clutch safety in hopes that the ECU would think it's in neutral.

but, when I put the automatic ECU in with the bypass, it worked...but threw check engine codes because there is no transmission.

Just to clarify: when you say that you swapped in the ECU for the automatic, are you referring to the main ECU or the transmission controller (TCU)?

I'm not clear on what if any sampling the ECU would do of the TCU to determine gear position on the AW4 - my gut feeling is that for extended idle operation it would only check the state of the NSS as reported by the TCU and use that as a go/no-go condition to kick in the extended idle (or not, as the case may be). Where it makes sense to me for it to operate in this way is that it shouldn't care which gear it's in, just that it's in park or neutral, so sampling the actual lever position wouldn't seem necessary.

This has me wondering if what's really needed is an NSS simulator that can feed the ECU with a bogus signal. Of course, that's based on the assumption that the ECU firmware for a manual-transmission XJ has the capability to do that - and even if it has that capability, if it's active when a manual transmission (and hence no TCU) is installed.

It might be worth picking up a TCU and NSS and seeing what the options are for installing them in a manual-transmission model. My experience with manual-transmission XJs is very limited at best, so this may be way more work than the end result would be worth.

Late edit: I need to learn to type faster than Kastein

 

[kastein]

Just to clarify: when you say that you swapped in the ECU for the automatic, are you referring to the main ECU or the transmission controller (TCU)?

I'm not clear on what if any sampling the ECU would do of the TCU to determine gear position on the AW4 - my gut feeling is that for extended idle operation it would only check the state of the NSS as reported by the TCU and use that as a go/no-go condition to kick in the extended idle (or not, as the case may be). Where it makes sense to me for it to operate in this way is that it shouldn't care which gear it's in, just that it's in park or neutral, so sampling the actual lever position wouldn't seem necessary.

This has me wondering if what's really needed is an NSS simulator that can feed the ECU with a bogus signal. Of course, that's based on the assumption that the ECU firmware for a manual-transmission XJ has the capability to do that - and even if it has that capability, if it's active when a manual transmission (and hence no TCU) is installed.

It might be worth picking up a TCU and NSS and seeing what the options are for installing them in a manual-transmission model. My experience with manual-transmission XJs is very limited at best, so this may be way more work than the end result would be worth.

Late edit: I need to learn to type faster than Kastein

Just an NSS simulator will work great while it's idling in P/N, but the TCU will get extremely unhappy about the fact that it's got no solenoids and no output speed sensor (thus the dummy load resistors) and if it's a 98 or later TCU will also get unhappy when the transmission doesn't shift as it expected it to (speed sensor signals) thus the 97 TCU idea. I'm also not certain about putting a TCU into an MT XJ, I think you'll at least need the ECU to be from an AT XJ for it to even bother checking for its presence.

 

[casm]

Just an NSS simulator will work great while it's idling in P/N, but the TCU will get extremely unhappy about the fact that it's got no solenoids and no output speed sensor (thus the dummy load resistors) and if it's a 98 or later TCU will also get unhappy when the transmission doesn't shift as it expected it to (speed sensor signals) thus the 97 TCU idea.

Good points. I'd completely forgotten about the solenoids & speed sensor.

I'm also not certain about putting a TCU into an MT XJ, I think you'll at least need the ECU to be from an AT XJ for it to even bother checking for its presence.

One more item to add to the list of things to check if I can ever get my hands on ECU firmware for the XJ. It's almost at the point where I'm halfway tempted to send ECUs for a few different years out to someone with better dumping equipment than I have access to and see what comes back.

 

[kastein]

Good points. I'd completely forgotten about the solenoids & speed sensor.



One more item to add to the list of things to check if I can ever get my hands on ECU firmware for the XJ. It's almost at the point where I'm halfway tempted to send ECUs for a few different years out to someone with better dumping equipment than I have access to and see what comes back.

I pried a '99 open to take a look inside it, as I recall it has an MC68k series processor with the batwings on it, and firmware is stored in a run of the mill Intel 28Fxxxx series flash chip. One of these decades, I'll get around to messing with it...

 

[jeepcomj]

I installed an ECU. if I had meant TCU, I would have said TCU.


I can tell you now that you will need TONS of wiring on a 5 speed to even make it possible to pop a TCU in there. there are no connectors for it, there are no mounts for the TCU under the dash, above the gas pedal, where it is located from factory. there is no wiring for it.

so, your deduction that the TCU is needed plus the aw4 NSS is probably correct. above that, though...a 5 speed ECU throws a CEL in an aw4 xj (tested this on my room mate's '97), and it won't shift. that tells me that the 5 speed ECU simply isn't capable.


you'd be better off making an adjustable voltage regulator/resistor to the IAC actuator/sensor. that's all the ECU does is adjust that to bump the idle.

hand throttles are for idiots. you bump it, you're screwed. there's no way to make it be disengage-able, save for disconnecting it when you're not on the trails. at least with an idle switch you could have an "arm" switch so it can't be accidently bumped.

 

[kastein]

I installed an ECU. if I had meant TCU, I would have said TCU.


I can tell you now that you will need TONS of wiring on a 5 speed to even make it possible to pop a TCU in there. there are no connectors for it, there are no mounts for the TCU under the dash, above the gas pedal, where it is located from factory. there is no wiring for it.

so, your deduction that the TCU is needed plus the aw4 NSS is probably correct. above that, though...a 5 speed ECU throws a CEL in an aw4 xj (tested this on my room mate's '97), and it won't shift. that tells me that the 5 speed ECU simply isn't capable.


you'd be better off making an adjustable voltage regulator/resistor to the IAC actuator/sensor. that's all the ECU does is adjust that to bump the idle.

hand throttles are for idiots. you bump it, you're screwed. there's no way to make it be disengage-able, save for disconnecting it when you're not on the trails. at least with an idle switch you could have an "arm" switch so it can't be accidently bumped.

I'm not sure you can do that with the IAC, it is a bipolar 2 phase stepper motor on 91+ XJs. Considered a way to do this but it's really not that easy, in effect it would end up being an electronic hand throttle even if it was possible - the ECU implements extended idle by watching the signal from the CPS and adjusting the idle air supply with the IAC to get 1000+rpm instead of 750, unless you somehow fooled it into thinking the engine is turning slower than it is, the idle control will no longer be closed loop... i.e. it'll be just a different more complicated hand throttle. The problem in fooling the ECU into thinking the engine is spinning slower than it really is is that it will go haywire trying to control fuel/ignition/timing and it's fairly complicated to do.

 

[casm]

I pried a '99 open to take a look inside it, as I recall it has an MC68k series processor with the batwings on it, and firmware is stored in a run of the mill Intel 28Fxxxx series flash chip. One of these decades, I'll get around to messing with it...

That's a lot further along than I've got with it - the junkyards around here want stupid money for working ECUs, and I just can't put the cash into this project at this time. Good to know it looks fairly normal so far, though; the real WTF will be how to extract the firmware. Could be easy, could be a PITA.

Anyway, food for thought. I'll quit hijacking the thread now.

 

[kastein]

The biggest difficulty for me would be reverse engineering the I/O hardware and also figuring out the address map. Pulling the ROM and dumping it is pretty easy when all is said and done.

I pay approx $50 for ECUs up here. I got the '99 one for like $10 at a part-out because I also bought the entire drivetrain, the radiator, and portions of the interior as well as the ACM and TCU.

 

[casm]

The biggest difficulty for me would be reverse engineering the I/O hardware and also figuring out the address map. Pulling the ROM and dumping it is pretty easy when all is said and done.

Agreed on both counts - but given that it's 68K-based, this may not be a total nightmare. Assuming that it's a vanilla 68K and there's not some horrible MCU or similar in use as an anti-piracy measure, it should be possible to dump the firmware, write a skeleton driver for MAME or MESS' 68K core, run the firmware in debug mode, see where it tries to read and write from, and go from there.

Note that I'm not saying this is necessarily the best approach, but should at least give a running head start at it.

I pay approx $50 for ECUs up here. I got the '99 one for like $10 at a part-out because I also bought the entire drivetrain, the radiator, and portions of the interior as well as the ACM and TCU.

$200-$300 is about the going rate around here for 'tested' ECUs; by 'tested', what they really mean is, "we turned the key and it started". Right now, though, I can't even free up $50 for this with inspection-grade maintenance looming and the other projects I've got in mind.

 

[kastein]

Agreed on both counts - but given that it's 68K-based, this may not be a total nightmare. Assuming that it's a vanilla 68K and there's not some horrible MCU or similar in use as an anti-piracy measure, it should be possible to dump the firmware, write a skeleton driver for MAME or MESS' 68K core, run the firmware in debug mode, see where it tries to read and write from, and go from there.

Note that I'm not saying this is necessarily the best approach, but should at least give a running head start at it.



$200-$300 is about the going rate around here for 'tested' ECUs; by 'tested', what they really mean is, "we turned the key and it started". Right now, though, I can't even free up $50 for this with the other projects I've got in mind.

Yeah, my thought was to desolder the MCU (it looked like an actual microprocessor, not an MCU actually - the firmware is external and in a standard flash chip so there should not be any protection on it) and cycle through all the addresses while watching the chipselect pin status on any bus-connected chips. Should give a full map with no difficulty. The chip had the motorola batwings on it, so I think it should be no problem... I just don't know 68k assembly yet. The real difficulty is that most of the I/O chips appeared to have custom chrysler part numbers on them, which makes it a real bear to look up datasheets.

Agreed on the ECU cost, stuff gets expensive.

Anyone in Mass/CT/RI/southern VT or NH have a 97+ stock manual XJ, preferably a 98 or later, and a spare ECU that is for the proper year but from an auto? I would like to try the 97 TCU, proper year AT ECU, and dummy load resistor approach but don't have a stock M/T late model XJ to play with.

If it works, you get working extended idle :thumbup: