Need the XJ to run HOTTER
CF Veteran
Joined: Apr 2009
Posts: 4,734
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Year: 2015, 2012
Model: Grand Cherokee (WK2)
Engine: 3.6L
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,579
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
All myths aside, after using 3 Stant 195* Superstats and warrantying 2 of them, the Mopar stats did what I wanted. They gave me quick warm-up in sub-freezing weather, proper 195* operating temp, and more stable temps on hot days.
So, dumb old me used FIVE of those stats, purchased from Napa, before I learned my lesson.
I am a firm believer in them.
Don't knock em til you try them. 52028186.
So, dumb old me used FIVE of those stats, purchased from Napa, before I learned my lesson.
I am a firm believer in them.
Don't knock em til you try them. 52028186.
Last edited by cruiser54; Oct 23, 2014 at 09:02 PM.
CF Veteran
Joined: Nov 2009
Posts: 8,172
Likes: 17
From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
https://search.yahoo.com/search?ei=u...ors%20do&type=
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
Regardless, the closed loop transition has always functioned in the same manner.
Not at all. OBD-I is a horrible mess that is a pain in the *** to troubleshoot that was never standardized and generally sucks *****. In early OBD-II the downstream O2 sensor was only used to illuminate a CEL.
For example, emissions was a pretty big deal on the Renix platform, running hot by design and equipped with O2 sensor, EGR, and catalytic converter.
Sounds like a bet...
The following is from the 1995 XJ FSM. Section J covers the Chrysler OBD-I fuel system used in XJs and YJs.
OPEN LOOP/CLOSED LOOP MODES OF OPERATION
As input signals to the powertrain control module (PCM) change, the PCM adjusts its response to the output devices. For example, the PCM must calculate different injector pulse width and ignition timing for idle than it does for wide open throttle (WOT). There are several different modes of operation that determine how the PCM responds to the various input signals.
MODES
During Closed Loop modes, the PCM will monitor the oxygen (O2S) sensor input. This input indicates to the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the exhaust oxygen content through the O2S sensor, the PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined with low emission engine performance.
The fuel injection system has the following modes
of operation:
As input signals to the powertrain control module (PCM) change, the PCM adjusts its response to the output devices. For example, the PCM must calculate different injector pulse width and ignition timing for idle than it does for wide open throttle (WOT). There are several different modes of operation that determine how the PCM responds to the various input signals.
MODES
- Open Loop
- Closed Loop
During Closed Loop modes, the PCM will monitor the oxygen (O2S) sensor input. This input indicates to the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the exhaust oxygen content through the O2S sensor, the PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined with low emission engine performance.
The fuel injection system has the following modes
of operation:
- Ignition switch ON
- Engine start-up (crank)
- Engine warm-up
- Idle
- Cruise
- Acceleration
- Deceleration
- Wide open throttle (WOT)
- Ignition switch OFF
When engine has reached operating temperature, the PCM will begin monitoring O2S sensor input. The system will then leave the warm-up mode and go into closed loop operation.
The resistance [of the engine coolant temperature sensor] should be less than 1000 ohms with the engine at its correct operating temperature. Refer to the Coolant Temperature Sensor/Manifold Air Temperature Sensor resistance chart.
The following is taken from the 2005 TJ FSM, a full 10 years and one "evil EPA wacko" fuel system later. Astoundingly, it works the same way:
DESCRIPTION - MODES OF OPERATION
As input signals to the Powertrain Control Module (PCM) change, the PCM adjusts its response to the output devices. For example, the PCM must calculate different injector pulse width and ignition timing for idle than it does for wide open throttle (WOT).
The PCM will operate in two different modes:
Open Loop and Closed Loop.
During Open Loop modes, the PCM receives input signals and responds only according to preset PCM programming. Input from the oxygen (O2S) sensors is not monitored during Open Loop modes. During Closed Loop odes, the PCM will monitor the oxygen (O2S) sensors input. This input indicates to the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the exhaust oxygen content through the O2S sensor, the PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined with low emission engine performance.
The fuel injection system has the following modes of operation:
As input signals to the Powertrain Control Module (PCM) change, the PCM adjusts its response to the output devices. For example, the PCM must calculate different injector pulse width and ignition timing for idle than it does for wide open throttle (WOT).
The PCM will operate in two different modes:
Open Loop and Closed Loop.
During Open Loop modes, the PCM receives input signals and responds only according to preset PCM programming. Input from the oxygen (O2S) sensors is not monitored during Open Loop modes. During Closed Loop odes, the PCM will monitor the oxygen (O2S) sensors input. This input indicates to the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the exhaust oxygen content through the O2S sensor, the PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined with low emission engine performance.
The fuel injection system has the following modes of operation:
- Ignition switch ON
- Engine start-up (crank)
- Engine warm-up
- Idle
- Cruise
- Acceleration
- Deceleration
- Wide open throttle (WOT)
- Ignition switch OFF
ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warmup, the PCM receives inputs from:
This is an Open Loop mode. During engine warmup, the PCM receives inputs from:
- Battery voltage
- Crankshaft position sensor
- Engine coolant temperature sensor
- Intake manifold air temperature sensor
- Manifold absolute pressure (MAP) sensor
- Throttle position sensor (TPS)
- Camshaft position sensor signal (in the distributor)
- Park/neutral switch (gear indicator signal—auto. trans. only)
- Air conditioning select signal (if equipped)
- Air conditioning request signal (if equipped)
- Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.
- The PCM adjusts engine idle speed through the idle air control (IAC) motor and adjusts ignition timing.
- The PCM operates the A/C compressor clutch through the A/C compressor clutch relay. This is done if A/C has been selected by the vehicle operator and specified pressures are met at the high and low–pressure A/C switches. Refer to Group 24, Heating and Air Conditioning for additional information.
- When engine has reached operating temperature, the PCM will begin monitoring O2S sensor input. The system will then leave the warm-up mode and go into closed loop operation.
Just for fun lets get really old. I have a copy of the Renix Fuel Injection manual that goes into some detail...
OPEN LOOP VS CLOSED LOOP
Air fuel control is achieved by two operational strategies: OPEN LOOP and CLOSED LOOP control. In OPEN LOOP operation, the air/fuel mixture is determined primarily by the MAP, engine speed, and engine coolant temperature sensors.
In CLOSED LOOP operation, the above sensors provide information for the ECU to establish a base injector pulse width, but the Exhaust Oxygen Sensor signal is used to indicate whether or not the calculated injector pulse results in the proper air/fuel ratio of 14.7 part air to 1 part fuel. By monitoring the exhaust oxygen sensor content with the Exhaust Oxygen Sensor, the base injector pulse width can be modified to achieve the optimum air/fuel ratio. An example of CLOSED LOOP operation is a thermostatically controlled household heating system. As the temperature in the house falls below the setting of the thermostat, a signal is sent to the furnace. The furnace is turned ON, and heat is provided. As the temperature of the house rises past the thermostat setting, the signal is interrupted and the furnace shuts off.
OPEN LOOP OR CLOSED LOOP DETERMINATION
Operating temperature is determined by the ECU as a result of the Engine Coolant and Manifold Air Temperature Sensor signals. The engine is in CLOSED LOOP operation if it is at sufficient operating temperature and either in an idle or cruise condition. At these conditions, the Exhaust Oxygen Sensor is factor in determining the proper air/fuel mixture.
When the engine is not at a calibrated operating temperature, fuel calculations are based on an OPEN LOOP strategy.
Air fuel control is achieved by two operational strategies: OPEN LOOP and CLOSED LOOP control. In OPEN LOOP operation, the air/fuel mixture is determined primarily by the MAP, engine speed, and engine coolant temperature sensors.
In CLOSED LOOP operation, the above sensors provide information for the ECU to establish a base injector pulse width, but the Exhaust Oxygen Sensor signal is used to indicate whether or not the calculated injector pulse results in the proper air/fuel ratio of 14.7 part air to 1 part fuel. By monitoring the exhaust oxygen sensor content with the Exhaust Oxygen Sensor, the base injector pulse width can be modified to achieve the optimum air/fuel ratio. An example of CLOSED LOOP operation is a thermostatically controlled household heating system. As the temperature in the house falls below the setting of the thermostat, a signal is sent to the furnace. The furnace is turned ON, and heat is provided. As the temperature of the house rises past the thermostat setting, the signal is interrupted and the furnace shuts off.
OPEN LOOP OR CLOSED LOOP DETERMINATION
Operating temperature is determined by the ECU as a result of the Engine Coolant and Manifold Air Temperature Sensor signals. The engine is in CLOSED LOOP operation if it is at sufficient operating temperature and either in an idle or cruise condition. At these conditions, the Exhaust Oxygen Sensor is factor in determining the proper air/fuel mixture.
When the engine is not at a calibrated operating temperature, fuel calculations are based on an OPEN LOOP strategy.
WARM-UP MODE
OPEN LOOP
During warm up the ECU receives information from the following inputs:
The ECU operates the air conditioning clutch through the clutch relay if air conditioning has been selected by the driver and requested by the A/C thermostat. The ECU determines and controls the proper ignition timing. On vehicles equipped with manual transmissions, the shift indicator light is operated by the ECU based on engine speed and load. This indicates to the driver that a gear change is suggested. If the suggested shift is not performed, the ECU will turn the light out after 3 to 5 seconds.
The EGR solenoid is energized by the ECU to restrict EGR operation. Based on engine coolant temperature and a timer, the ECU determines the duration of the warm up period. When the ECU determines that the engine has reached operating temperature, input from the exhaust oxygen sensor is checked and the system goes into closed loop operation. This signifies the end of the Warm-Up mode.
OPEN LOOP
During warm up the ECU receives information from the following inputs:
- Coolant temperature sensor
- Manifold air temperature sensor
- Manifold absolute pressure (MAP) sensor
- Throttle position sensor
- Engine speed sensor signal
- Sync signal generator
- Battery voltage
- Gear indicator signal (automatic only)
- Air conditioning select signal (if equipped)
- Air conditioning request signal (if equipped)
- Knock sensor
- Oxygen sensor
- Coolant temperature sensor
- Manifold air temperature sensor
- Manifold absolute pressure (MAP) sensor
- Throttle position sensor
- Engine speed sensor signal
- Oxygen sensor
The ECU operates the air conditioning clutch through the clutch relay if air conditioning has been selected by the driver and requested by the A/C thermostat. The ECU determines and controls the proper ignition timing. On vehicles equipped with manual transmissions, the shift indicator light is operated by the ECU based on engine speed and load. This indicates to the driver that a gear change is suggested. If the suggested shift is not performed, the ECU will turn the light out after 3 to 5 seconds.
The EGR solenoid is energized by the ECU to restrict EGR operation. Based on engine coolant temperature and a timer, the ECU determines the duration of the warm up period. When the ECU determines that the engine has reached operating temperature, input from the exhaust oxygen sensor is checked and the system goes into closed loop operation. This signifies the end of the Warm-Up mode.
Annoyingly the Renix manual doesn't actually say what normal operating temperature is, either!
However it's pretty clear to me that closed loop is, and always has been, chosen mostly based on whatever the ECT says. What exactly this number is probably varies depending on year. So far we have PocketsEmpty's video showing that it could be 90°F on a 1998 edition PCM. At very the least there is a lot of experimentation showing that it's far before 195°F.
Hang out by the muffler and smell the fumes coming out and tell me if you think that is "closed loop" after letting it run for 30 seconds per the video. If it smells like un-burned exhaust fumes, especially after passing through a catalytic converter, it clearly is NOT in closed loop.
CF Veteran
Joined: Nov 2009
Posts: 8,172
Likes: 17
From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
......and I've been using Stant stats for a lifetime with excellent results. I think they make good crap at a fair price. When I'm asked "what's in your wallet?.....I can honestly say, money". Time to pop-a-top again, with the money I save. Thanks to a crappy Stant stat, our XJ warms up quickly, makes good heat in the winter and stays reasonably cool in the summer and I'm sure a dealer stat works just as good......but with a lot more cha-ching. LOL
$25 for a freakin' MotoRad from the dealer that won't even "fail safe"......really?
$25 for a freakin' MotoRad from the dealer that won't even "fail safe"......really?
Last edited by djb383; Oct 23, 2014 at 09:26 PM.
CF Veteran
Joined: Nov 2009
Posts: 8,172
Likes: 17
From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
Yikes salad. BS, popcorn, and testosterone have taken over this thread.
Just trying to keep things light....it's sad it's turned into a boxing match.
That's partly my fault, but not totally, so my bad.
The ScanGauge (and other scan tools) will clearly show "closed" loop being entered well before the ECT is anywhere near so called operating temp. The ECU sends a "closed" loop signal to the scan tool for display by the scan tool. The results r the same when the ScanGauge is plugged into our XJ, Toyota, GMC, Saturn, Pontiac and our neighbors Furd and Isuzu......those systems as well enter "closed" loop well before the ECT sees even 100F.
From what I've observed, the time to go from open to closed loop is not much different whether the motor is hot or cold. Exhaust components (including the O2) will cool rapidly after a hot motor has been turned off and sits for say 15-20 minutes. In 15-20 minutes coolant is still close to the running temp but the O2 has cooled substantially (depending on where it's located). Closed loop is not entered the second a hot motor is started.....there is a delay just like in a cold start but not as long.
Just trying to keep things light....it's sad it's turned into a boxing match. That's partly my fault, but not totally, so my bad. The ScanGauge (and other scan tools) will clearly show "closed" loop being entered well before the ECT is anywhere near so called operating temp. The ECU sends a "closed" loop signal to the scan tool for display by the scan tool. The results r the same when the ScanGauge is plugged into our XJ, Toyota, GMC, Saturn, Pontiac and our neighbors Furd and Isuzu......those systems as well enter "closed" loop well before the ECT sees even 100F.
From what I've observed, the time to go from open to closed loop is not much different whether the motor is hot or cold. Exhaust components (including the O2) will cool rapidly after a hot motor has been turned off and sits for say 15-20 minutes. In 15-20 minutes coolant is still close to the running temp but the O2 has cooled substantially (depending on where it's located). Closed loop is not entered the second a hot motor is started.....there is a delay just like in a cold start but not as long.
Last edited by djb383; Oct 23, 2014 at 10:00 PM.
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Joined: Aug 2011
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From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
The ScanGauge (and other scan tools) will clearly show "closed" loop being entered well before the ECT is anywhere near so called operating temp. The ECU sends a "closed" loop signal to the scan tool for display by the scan tool. The results r the same when the ScanGauge is plugged into our XJ, Toyota, GMC, Saturn, Pontiac and our neighbors Furd and Isuzu......those systems as well enter "closed" loop well before the ECT sees even 100F.
CF Veteran
Joined: Dec 2012
Posts: 4,169
Likes: 6
From: York, PA
Year: 1998
Model: Cherokee
Engine: 4.0
From what I've observed, the time to go from open to closed loop is not much different whether the motor is hot or cold. Exhaust components (including the O2) will cool rapidly after a hot motor has been turned off and sits for say 15-20 minutes. In 15-20 minutes coolant is still close to the running temp but the O2 has cooled substantially (depending on where it's located). Closed loop is not entered the second a hot motor is started.....there is a delay just like in a cold start but not as long.
CF Veteran
Joined: Nov 2009
Posts: 8,172
Likes: 17
From: The Republic of TEXAS
Year: 1998
Model: Cherokee
Engine: 4.0L HO
It's also interesting to see how various driving conditions will kick the system out of "closed" loop and back into "open" loop" momentarily. Things like throttle position, manifold pressure, etc., also come into play to determine open/closed loop.
U gotta have a on-board scan tool to see the back and forth, open/closed loop, transitions while driving. Kinda hard to sniff/smell a tailpipe at 75 mph to determine when the loop is open/closed.
U gotta have a on-board scan tool to see the back and forth, open/closed loop, transitions while driving. Kinda hard to sniff/smell a tailpipe at 75 mph to determine when the loop is open/closed.
Herp Derp Jerp
Joined: Nov 2011
Posts: 18,251
Likes: 17
From: Parham, ON
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
My boss got a decent one, after looking at reviews and specs it actually was the cheapest decent one. $100 got him the app and the adaptor. Not the answer you're looking for but you're MUCH better off picking up a used Android unit and an ELM327