Gas mileage... w00t!

[cygnus58]

Turning on the headlights would be the same as grounding out the positive cable... with no battery connected the direct link from the headlights would also bleed off any extraneous voltage. you both are right!!
Two cigars...

 

[Ecomike]

Turning on the headlights would be the same as grounding out the positive cable... with no battery connected the direct link from the headlights would also bleed off any extraneous voltage. you both are right!!
Two cigars...

Except that the instructions said to re-attach the positive cable to the battery +post, then to turn the ignition on then to turn the headlights on.

If it was just a matter of grounding everything I would turn the ignition on (after removing the +battery cable) and then I would ground it.

 

[jpk]

Got this from one of the guys over on blue mountain who got it from somewhere else, not sure of the validity of it but it sounds very plausable to me from being in the computer business.
posted on rof by elff


PCM Fast Learn Mode
I think most people know that the PCM performs several functions controlling Air Fuel ratios via Injector Pulse Width and Ignition Timing.

These “outputs” are controlled using the “inputs” received from all the sensors and then comparing these reading against a set of data tables burned into the PCM.

These “memory tables” are the brains that keep the engine running at low emissions and peak economy across the RPM band

What most people don’t know is that these memory tables change. They are “adaptive”, based on sensor readings, driving habits, engine performance and sensor tolerances.

Over time, the PCM Memory Tables become tuned to your engine.

Most folks know that disconnecting the battery for 15 to 20 minutes will reset the PCM to get rid of a Check Engine Light or Error Codes stored in the PCM.

However this DOES NOT reset the Adaptive Memory Tables in the PCM. Until recently I did not know how to do this.

This procedure first came to me from the folks at Avenger. I then verified it with a phone call to a Chrysler Engineer who had called me a year or so ago to ask about my experiences with a certain part on my TJ. I figured he owned me a favor. He had to check up on this for me. He called me back a week later and did indeed verify this procedure and what it does.

To the best of my knowledge it isn’t documented in any of the FSM.

Forced Flash

This very simple procedure will Erase the “Adaptive Memory” stored inside the TJ PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

[L]Disconnect the POSITIVE battery Terminal and touch it to ground for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.
Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”[/L]

Adaptive memory has nor been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

Warm-up Cycle

A warm-up cycle happens when all of the following conditions exist.

Engine is running
A raise of 40F in engine temperature must occur ABOVE the engine temperature at start-up
Engine Coolant Temp must reach at least 160 F.

Once your engine has gone through 50 warm-up cycles in at least a 500-mile distance the PCM adaptive memory is set. It WILL NOT Change unless you flash it out and start all over again.

When you say to ground the positive cable, what do you mean, where would I ground it too? Do you mean ground it to the chassis or another ground off the vehicle?

My XJ is a 96 Country that until recently was a North Carolina vehicle. It now resides in N. Florida so the driving conditions would be much different. Also the driver was a woman so perhaps with much different driving habits. Might my XJ benefit from a reflash?

 

[RichP]

When you say to ground the positive cable, what do you mean, where would I ground it too? Do you mean ground it to the chassis or another ground off the vehicle?

My XJ is a 96 Country that until recently was a North Carolina vehicle. It now resides in N. Florida so the driving conditions would be much different. Also the driver was a woman so perhaps with much different driving habits. Might my XJ benefit from a reflash?

What it means is remove the +12V Red battery cable from the battery at the battery terminal. Any circuits that are retaining any residual charge will bleed off once you touch that +12 lead THAT IS DISCONNECTED FROM THE BATTERY and will or should reset any solid state switches or gates or whatever in the ignition system.
Just so we are VERY clear on this YOU DO NOT WANT TO TOUCH THE +12V side of the BATTERY to ground, you do not want to short the +12V side of the battery to ground.
God I don't want someone to mis read this.
For a failsafe, no errors method, REMOVE THE BATTERY FROM THE JEEP, PUT IN A LOCKED WOODEN BOX 20Ft away, THEN TOUCH THE +12V battery lead to ground in the jeep, you can even touch it to the other ground lead that was previously connected to the battery. I would leave it like that for about 20-30 minutes just to make sure you get all the slow caps to discharge if there are any in there, I don't know. I can see the logic about my posting but have not tried it nor have I had the problems that caused this procedure to be necessary. Once you have done this you can then open the wooden box and reinstall the battery..

 

[Ecomike]

Just so we are VERY clear on this YOU DO NOT WANT TO TOUCH THE +12V side of the BATTERY to ground, you do not want to short the +12V side of the battery to ground.
God I don't want someone to mis read this.

God, I can't possibly imagine why not, after all, all it would do is weld the battery cable with a large show of sparks, short out the battery, discharge the battery in a few seconds and explode the battery throwing molten lead and hot acid all over the fool that did it. :doh:

Just thought I would draw them a verbal picture of why not to do it the wrong way!

 

[RichP]

God, I can't possibly imagine why not, after all, all it would do is weld the battery cable with a large show of sparks, short out the battery, discharge the battery in a few seconds and explode the battery throwing molten lead and hot acid all over the fool that did it. :doh:

Just thought I would draw them a verbal picture of why not to do it the wrong way!

I was afraid I might have over done it

 

[Ecomike]

I was afraid I might have over done it

I was think the same thing, the box holding the battery probably only needs to be 15 feet away, :cheers:, :rof:

But then again with some people 30 Ft might be needed, LOL.

Back to the topic, I am hoping some of the OBD-1 owners will try this and post some interesting results on their mileage and performance.

I found out recently that the TCU (87-96) and the Renix ECU (87-90) have a "hot all the time" 12 volt wire running to them both, that is obviously there for one reason, to preserve operating and sensor data table values. I also found seperate FSM text on both the TCU and the Renix ECU to support this.

What I also found interesting in my case, was that the 12 volt, hot all the time wire to MY TCU was dead all the time! I will be investigating that issue as soon as I have finished my roundtoit A/C :sunshine:work before it gets any hotter here!

 

[artsifrtsi]

So on my Renix, I should be able to just disconnect power and ground out the power to clear out the flash, right? I may have to give that a try this weekend.

On the Pos battery term grounded to the neg, it won't matter if the battery is in or out, so long as there is no other source of power, IE 2nd battery. DC cannot flow without a place to flow to.

 

[MrShaft696]

Took my Jeep on a trip yesterday from Carthage, NY to Schenectady, NY and averaged 20.1 MPG! Things have been getting better and better on this rig. I started off with an almost outrageous 15 MPG, fixed the dragging brake and mileage went up to 17. Ran Seafoam through her, and in addition to the oil pressure increasing to ~75 on startup to ~65 at running temp (according to factory dash gauge) mileage went up to 18.7 mixed and now the big test at 20.1! I am loving this 210,000 mile rig more and more every day!

(Oh, and this rig is a 1990 2 door with 4.0 l and an AX15, has a 2 inch lift, 31's and original 3.55:1 gearing)

Now I cannot wait to get going with the next set of mods, and improving the body!

you have 3.07s unless the trans was converted or the gears were swapped

 

[Ecomike]

So on my Renix, I should be able to just disconnect power and ground out the power to clear out the flash, right? I may have to give that a try this weekend.

On the Pos battery term grounded to the neg, it won't matter if the battery is in or out, so long as there is no other source of power, IE 2nd battery. DC cannot flow without a place to flow to.

Yes, but you are scaring me a bit here (maybe just the wording you used). Make sure the positive cable is completely disconnected from the battery (or all batteries as you pointed out), then ground that positive cable to the chasis or the negative battery cable. Make sure nothing is attached to the positive battery terminal(s)!:shiver:

 

[Ba-Riedo]

so will this work on a 98?

 

[Blaine B.]

So you touch positive battery terminal clamp (after removing it from the battery) to the negative battery teminal?

How about the other way around?

 

[cygnus58]

When I installed liquid hydrogen cooled supermagnets on my '88 4.0 fuel rail input, I actually noticed the gas gauge would rise after a few miles. This required a "fuel overflow" tank system.
I also installed a vent unit for the magnet system to introduce cooler air into the passenger compartment.
Now I don't have to troubleshoot my A/C either.
I just have to find a cheaper source for the liquid hydrogen.

 

[Blaine B.]

Say what?

 

[cygnus58]

just being stupid, alot of that in my head tonite i guess..

 

[Blaine B.]

Oh.

 

[Ackattack]

In my first tank through the 90 MJ I got about 18 driving back and forth to work (15 mile highway 5 miles city) Now that I got my oil leak solved maybe I'll run some seafoam through it.

On the other hand my 4.0L ZJ with 33s and 4.56 gears gets about 14 mpg highway and 10 city. I think the best average tank I've gotten is 13....

 

[jpk]

What it means is remove the +12V Red battery cable from the battery at the battery terminal. Any circuits that are retaining any residual charge will bleed off once you touch that +12 lead THAT IS DISCONNECTED FROM THE BATTERY and will or should reset any solid state switches or gates or whatever in the ignition system.
Just so we are VERY clear on this YOU DO NOT WANT TO TOUCH THE +12V side of the BATTERY to ground, you do not want to short the +12V side of the battery to ground.
God I don't want someone to mis read this.
For a failsafe, no errors method, REMOVE THE BATTERY FROM THE JEEP, PUT IN A LOCKED WOODEN BOX 20Ft away, THEN TOUCH THE +12V battery lead to ground in the jeep, you can even touch it to the other ground lead that was previously connected to the battery. I would leave it like that for about 20-30 minutes just to make sure you get all the slow caps to discharge if there are any in there, I don't know. I can see the logic about my posting but have not tried it nor have I had the problems that caused this procedure to be necessary. Once you have done this you can then open the wooden box and reinstall the battery..

I didn't think you had meant to ground the positive to the frame, etc. with the neg still connected. Yes, there would be a fireworks display.

 

[RichP]

I didn't think you had meant to ground the positive to the frame, etc. with the neg still connected. Yes, there would be a fireworks display.

Sometimes you have to be really really careful, I was telling a neighbor next door on the phone who was having a hard time getting his YJ started with one of those carter BBL's. Suggested pouring a bit of gas down the bore, neglected to say 'keep your face away when you daughter turns the key', I head the woomph, saw the flash thru the kitchen window followed by really loud swearing, he was more pissed about not having eyebrows anymore and gave me dirty looks for about a week.

 

[Ecomike]

Sometimes you have to be really really careful, I was telling a neighbor next door on the phone who was having a hard time getting his YJ started with one of those carter BBL's. Suggested pouring a bit of gas down the bore, neglected to say 'keep your face away when you daughter turns the key', I head the woomph, saw the flash thru the kitchen window followed by really loud swearing, he was more pissed about not having eyebrows anymore and gave me dirty looks for about a week.

Sounds like the one where they were were trying to blow out a clogged pipe (kitchen sink) and nothing was happening, so the guy looked into the sink drain outlet just as it uncloged. As I recall he was not a happy camper either. Gave a whole new meaning to getting shXtfaced!

:yelclap: Nice when these stories end with a out any real serious injuries.

In my case I was lucky I was in the car cranking a no start Dodge when the battery :fuse: blew up. Threw battery acid all over the place. Big mess. I keep my distance from questionable battery starting systems now while they are being cranked.