Fake Brake
02-20-2015, 07:50 AM
#18
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Join Date: Jul 2011
Location: Warren, Pa
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Year: 97
Model: Cherokee
Engine: 4.0L
Nothing that I know of. Last 3 of them have done that. After I get back in the throttle, it only stays unlocked for about half a second but, it's still super annoying. Could have something to do with stock gears and 35's tho
02-20-2015, 08:08 PM
#19
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Join Date: Sep 2013
Location: Tunkhannock, PA
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Year: 2000
Model: Cherokee
Engine: 4.0
According to the shop manual (XJ 1997 - 2001) AW4 pg 21-219. "Overdrive one way clutch - When transmission is driven by engine, connects sun gear and overdrive carrier." That would indicate that when the engine isn't powering the trans it will disconnect. It will also disconnect when the brake is applied. My 2000 operates this way, it puts it into a "free wheel" mode this is probably done to increase gas mileage. I have driven other cars that operate this way, usually the newer ones have a button on the shift lever to disengage OD which adds engine breaking. The older XJ models may not "free wheel" I don't know.
02-20-2015, 09:13 PM
#21
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Year: 1989
Model: Cherokee
Engine: 4.0
I am surprised the newer 4.0's don't have DFCO built in.
The Renix's do.
Quote from the Jeep Renix manual:
"Deceleration When the ECU senses a closed throttle condition through the Throttle Position Sensor and engine speed over 1200 rpm, the engine is in a deceleration state and fuel injection is shut off. Fuel injection is resumed when engine speed decreased below 1200 rpm or if the accelerator pedal is depressed. The engine operates in OPEN LOOP during deceleration."
Are you POSITIVE the HO doesn't have DFCO? Maybe you have leaky injectors and the act of turning the key off cuts ignition resulting in that slight deceleration.
The Renix's do.
Quote from the Jeep Renix manual:
"Deceleration When the ECU senses a closed throttle condition through the Throttle Position Sensor and engine speed over 1200 rpm, the engine is in a deceleration state and fuel injection is shut off. Fuel injection is resumed when engine speed decreased below 1200 rpm or if the accelerator pedal is depressed. The engine operates in OPEN LOOP during deceleration."
Are you POSITIVE the HO doesn't have DFCO? Maybe you have leaky injectors and the act of turning the key off cuts ignition resulting in that slight deceleration.
Last edited by firehawk618; 02-20-2015 at 09:16 PM.
02-20-2015, 09:31 PM
#22
Herp Derp Jerp
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Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
So I'm looking through my 1999 XJ FSM in the AW4 section and am trying to understand how this thing works. As far as I can tell the "one-way clutch" mechanisms are installed after planetary gears. Their purpose is to keep the gears from spinning in *reverse*, not to prevent engine braking. In fact there's troubleshooting here for scenarios where the clutch is unlocking and there is NOT a certain manner of engine braking occurring.
Here's what I've got. Way too lazy this evening to fix formatting:
BNJeepsta, have you ever had issues with your NSS or brake pedal switch?
Yes, they sure do. You're late to the game LOL. 
Post #12 on the previous page. I can quote the relevant part of later model FSMs if you like.
Here's what I've got. Way too lazy this evening to fix formatting:
The brake switch is in circuit with the torque converter clutch solenoid. The switch disengages the
converter clutch whenever the brakes are applied.
The switch is mounted on the brake pedal bracket
and signals the transmission control module when
the pedal is pressed or released.
TORQUE CONVERTER
A three element torque converter is used for all
applications. The converter contains an impeller, stator, and turbine.
The AW–4 converters are all equipped with a converter clutch mechanism. The clutch consists of a
sliding clutch piston, clutch springs and the clutch
disc material (Fig. 4). The clutch provides optimum
torque transfer and economy when engaged.
The clutch disc is attached to the converter front
cover. The clutch piston and clutch springs are
attached to the turbine hub. The springs dampen
engine firing impulses and loads during the initial
phase of converter clutch engagement.
Clutch engagement is controlled by transmission
valve body solenoid number three and by the converter clutch relay valve. The solenoid channels line
pressure to the clutch through the relay valve at
clutch engagement speeds.
Torque converter clutch engagement occurs in second gear in 1–2 position; third gear in 3 position and
third and fourth gear in D position.
converter clutch whenever the brakes are applied.
The switch is mounted on the brake pedal bracket
and signals the transmission control module when
the pedal is pressed or released.
TORQUE CONVERTER
A three element torque converter is used for all
applications. The converter contains an impeller, stator, and turbine.
The AW–4 converters are all equipped with a converter clutch mechanism. The clutch consists of a
sliding clutch piston, clutch springs and the clutch
disc material (Fig. 4). The clutch provides optimum
torque transfer and economy when engaged.
The clutch disc is attached to the converter front
cover. The clutch piston and clutch springs are
attached to the turbine hub. The springs dampen
engine firing impulses and loads during the initial
phase of converter clutch engagement.
Clutch engagement is controlled by transmission
valve body solenoid number three and by the converter clutch relay valve. The solenoid channels line
pressure to the clutch through the relay valve at
clutch engagement speeds.
Torque converter clutch engagement occurs in second gear in 1–2 position; third gear in 3 position and
third and fourth gear in D position.
BNJeepsta, have you ever had issues with your NSS or brake pedal switch?
I am surprised the newer 4.0's don't have DFCO built in.
The Renix's do.
Quote from the Jeep Renix manual:
"Deceleration When the ECU senses a closed throttle condition through the Throttle Position Sensor and engine speed over 1200 rpm, the engine is in a deceleration state and fuel injection is shut off. Fuel injection is resumed when engine speed decreased below 1200 rpm or if the accelerator pedal is depressed. The engine operates in OPEN LOOP during deceleration."
Are you POSITIVE the HO doesn't have DFCO? Maybe you have leaky injectors and the act of turning the key off cuts ignition resulting in that slight deceleration.
The Renix's do.
Quote from the Jeep Renix manual:
"Deceleration When the ECU senses a closed throttle condition through the Throttle Position Sensor and engine speed over 1200 rpm, the engine is in a deceleration state and fuel injection is shut off. Fuel injection is resumed when engine speed decreased below 1200 rpm or if the accelerator pedal is depressed. The engine operates in OPEN LOOP during deceleration."
Are you POSITIVE the HO doesn't have DFCO? Maybe you have leaky injectors and the act of turning the key off cuts ignition resulting in that slight deceleration.
Post #12 on the previous page. I can quote the relevant part of later model FSMs if you like.
02-21-2015, 01:53 AM
#23
CF Veteran
Join Date: Jul 2011
Location: Warren, Pa
Posts: 2,164
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Year: 97
Model: Cherokee
Engine: 4.0L
So I'm looking through my 1999 XJ FSM in the AW4 section and am trying to understand how this thing works. As far as I can tell the "one-way clutch" mechanisms are installed after planetary gears. Their purpose is to keep the gears from spinning in *reverse*, not to prevent engine braking. In fact there's troubleshooting here for scenarios where the clutch is unlocking and there is NOT a certain manner of engine braking occurring.
Here's what I've got. Way too lazy this evening to fix formatting:
BNJeepsta, have you ever had issues with your NSS or brake pedal switch?
Yes, they sure do. You're late to the game LOL. Post #12 on the previous page. I can quote the relevant part of later model FSMs if you like.
Here's what I've got. Way too lazy this evening to fix formatting:
BNJeepsta, have you ever had issues with your NSS or brake pedal switch?
Yes, they sure do. You're late to the game LOL.
Post #12 on the previous page. I can quote the relevant part of later model FSMs if you like.
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