wideband o2 questions.
02-22-2015, 05:31 PM
#1
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wideband o2 questions.
I have a 3.0 and looking to put a wideband set up on it and need some help. Do I replace the stock o2 with the wideband and if so how would I tie it into the ecm? If not do I just leave the narrowband and just add the wideband and not hook up the signal wire? The reason for this is because I have done the flamethrower injectors and 7 mge vafm and now just need to tune the fuel air to get it right. I have a narrowband gauge in now and it looks like it's close but I have heard they ain't worth a damn so I need a wideband.
02-22-2015, 06:05 PM
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The wide band will work with a narrow band gauge but it will get needle slap on an analog gauge.
No need to spend any extra money on a wideband set up for Toyota OBD1 vehicles, You will get no benefit, But if your intentions to later install 5vz or RZ Go for it.
Suggest Analog gauge, OBD1 runs in a constant state of up and down flux so no steady number on a digital.
No need to spend any extra money on a wideband set up for Toyota OBD1 vehicles, You will get no benefit, But if your intentions to later install 5vz or RZ Go for it.
Suggest Analog gauge, OBD1 runs in a constant state of up and down flux so no steady number on a digital.
02-22-2015, 09:35 PM
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Here is a great example of how OBD1 and a AF gauge work together.
At a cruise the needle bounces up and down and a digital meter would never stay on a particular number.
During decel it pegs total lean because your not giving it gas and the PAIR valve also opens letting outside atmosphere to keep velocity and the extra O2 helps burn remaining unburnt fuel at the CAT.
When the engine goes into open loop during acceleration (WOT) you can see it move over to the rich side.
A wide band will give no more useful info then a narrow band can on OBD1.
There is no programming on OBD1 like OBD2 does so you cannot change how it funtions, You can fool or alter the signal from the sensors going to the ECU but the final sensor is the O2 sensor the ECU will always re adjust to try make stoich.
So just a standard narrow band will work fine.
I have run AF gauge for 12 years now and its helped to track down faults and to fine tune the AFM as you intend to do.
During decel it pegs total lean because your not giving it gas and the PAIR valve also opens letting outside atmosphere to keep velocity and the extra O2 helps burn remaining unburnt fuel at the CAT.
When the engine goes into open loop during acceleration (WOT) you can see it move over to the rich side.
A wide band will give no more useful info then a narrow band can on OBD1.
There is no programming on OBD1 like OBD2 does so you cannot change how it funtions, You can fool or alter the signal from the sensors going to the ECU but the final sensor is the O2 sensor the ECU will always re adjust to try make stoich.
So just a standard narrow band will work fine.
I have run AF gauge for 12 years now and its helped to track down faults and to fine tune the AFM as you intend to do.
02-23-2015, 05:59 PM
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Can you explain to me what that means? Doesn't the VAF only influence mixture in open loop (cold, or WOT)? In 95% of your driving, the O2 sensor (wide or narrow band) reports back whether there is any O2 in the exhaust, and the ECU constantly jiggles the injector open-time to keep the O2 going above and below "zero." Regardless of what's going on with the VAF.
Is this "tuning" just for the minute or so after you first start? (while still in open loop)
Or am I just missing the point of this altogether?
Is this "tuning" just for the minute or so after you first start? (while still in open loop)
Or am I just missing the point of this altogether?
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02-23-2015, 07:11 PM
#8
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I have a bigger afm and bigger 4 hole injectors so if you don't lean it out some it will run rich. Without having a ratio gauge you don't know how much to lean it out to get it right.
02-23-2015, 08:37 PM
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Well, a bigger AFM should mean more air, which isn't going to make anything "rich."
But it just doesn't work that way. In closed loop, there isn't anything you can do to change the mixture; the ecu is reading the O2 sensor, and setting injector open-time to get it right. It doesn't matter how big the holes are in the injector, or how big your induction is. The mixture is NOT being set blind.
Unless, of course, the injector holes are so big (or the induction so over sized) that you exceed the limits of the ECU. But then what are you going to adjust? Setting the rheostat in the AFM isn't going to add more (or less) air, all you're doing is lying to the ECU about how much air the engine is sucking (which lie the ECU ignores in closed loop). It isn't going to expand the ECU's limits.
Open loop is a different story, so messing with the VAF setting can cause driveability problems. But a wide-band O2 sensor shouldn't help there anyway; just like the narrow-band sensor, it has to heat up to give any reading at all. And once it's hot enough, it goes straight to closed loop.
Am I missing something?
But it just doesn't work that way. In closed loop, there isn't anything you can do to change the mixture; the ecu is reading the O2 sensor, and setting injector open-time to get it right. It doesn't matter how big the holes are in the injector, or how big your induction is. The mixture is NOT being set blind.
Unless, of course, the injector holes are so big (or the induction so over sized) that you exceed the limits of the ECU. But then what are you going to adjust? Setting the rheostat in the AFM isn't going to add more (or less) air, all you're doing is lying to the ECU about how much air the engine is sucking (which lie the ECU ignores in closed loop). It isn't going to expand the ECU's limits.
Open loop is a different story, so messing with the VAF setting can cause driveability problems. But a wide-band O2 sensor shouldn't help there anyway; just like the narrow-band sensor, it has to heat up to give any reading at all. And once it's hot enough, it goes straight to closed loop.
Am I missing something?
02-24-2015, 04:56 AM
#10
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If I'm hearing you right your saying I don't need to adjust anything to get my fuel air ratio right? If that is the case then I have already adjusted it and I need it back to where it's running right. I'm thinking it's lean and my narrowband ratio gauge says it's running a little lean if I'm reading it right, which is difficult do read but I do my best seeing it's a narrowband and bounces everywher, but I just want to get my fuel air ratio right that way my truck runs better and in not hurting it by leaning it out too much.
02-24-2015, 06:48 AM
#11
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I have a wideband O2 running independently of the Toyota system. It too bounces all over the place while driving.
I added a supra VAFM to the 3VZe OBD1 system, only to see that no matter how I adjusted the VAFM the ECU adjusted the mix based on the Toyota O2(narrowband). I also went back to using the stock VAFM. Dispite what others may say on the interwebs, I have seen no gain using a different VAFM. Simply put the VAFM IS sized for these engines correctly, I am including the 22re in that statement.
I like having a wideband gauge in the truck so I can monitor AFR, simnce OBD1 diagnostic codes leave a bit to be desired. If I were you I would add a wideband O2 like I did. The math that the ECU is doing may or may not be able to deal with the new injectors and VAFM, this is why I would use the independant wideband, so you can actually see what is happening rather then guessing.
Also, I have deleted the PAIR and EGR, and my wideband bouces similarly to the one in the video.
I added a supra VAFM to the 3VZe OBD1 system, only to see that no matter how I adjusted the VAFM the ECU adjusted the mix based on the Toyota O2(narrowband). I also went back to using the stock VAFM. Dispite what others may say on the interwebs, I have seen no gain using a different VAFM. Simply put the VAFM IS sized for these engines correctly, I am including the 22re in that statement.
I like having a wideband gauge in the truck so I can monitor AFR, simnce OBD1 diagnostic codes leave a bit to be desired. If I were you I would add a wideband O2 like I did. The math that the ECU is doing may or may not be able to deal with the new injectors and VAFM, this is why I would use the independant wideband, so you can actually see what is happening rather then guessing.
Also, I have deleted the PAIR and EGR, and my wideband bouces similarly to the one in the video.
02-24-2015, 07:39 AM
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Scope is absolutely correct in his description of how things work (as usual). Here's a bit more detail.
The ECU runs in two modes, open loop and closed loop. Open loop occurs primarily under three conditions. (1) cold engine (2) closed throttle (3) wide open throttle. Closed loop operation occurs under most normal driving conditions.
In open loop, the ECU takes data from various sensors (primarily VAFM, ECT, TPS, and RPM) and estimates proper timing and injector pulse width based on a big lookup table to get a mixture setting that's close to optimum. Generally it shoots for stoichiometric except in the case of wide-open throttle, in which case it enriches the mixture somewhat for better power and more resistance to knocking.
In closed loop operation, the ECU makes its best estimate as above, but then takes input from the O2 sensor to fine-tune the mixture to stoichiometric. This is necessary not so much for engine performance, but to optimize the operation of the "3-way" catalytic converter for minimum emissions. The narrow-band O2 sensor acts like a switch, putting out 0 volt when the mixture is even slightly lean, and 1V when the mixture is slightly rich. The ECU control loop adjusts the mixture about once/second such that the O2 sensor output continually oscillates between 0V and 1V when things are operating properly. That ensures that the average mixture is stoichiometric.
The ECU puts out a voltage on the VF1 terminal in the diag connector which indicates how much the open loop estimate was in error compared to the O2 sensor. If VF1 measures 2.5 volts, the open loop estimate was right on. If the voltage is below 2.5V, the open loop estimate was biased toward rich, and the O2 sensor is telling the ECU to move the mixture leaner. If the voltage is above 2.5V, the open loop estimate is biased toward lean, and the O2 sensor is asking for a richer mixture.
If VF1 is pegged at either 0V or 5 volts during what should be closed-loop operation, the ECU has run out of control range and can no longer bring the mixture back to stoichiometric based on the O2 sensor output. The ECU has about +/- 20% mixture control range from its open loop estimate before it runs into the limits. This limit is there in part so that a defective O2 sensor doesn't render the engine completely inoperative.
So, what happens when you modify the VAFM or the injector size. Effectively, the lookup table that the ECU uses to initially estimate the mixture is no longer quite correct, so in open loop operation it will not get as close to the right mixture as it should. It may or may not have enough control range to still get back to stoichiometric based on the O2 sensor output. You can help out the ECU by adjusting the VAFM so it uses a slightly different part of the lookup table which more closely represents the new reality.
You don't really need a wide-band sensor and meter to adjust things. You can tweak things by putting a meter on the VF1 terminal and driving around. Once the engine warms up, check the voltage. If it is consistently below 2.5 volts in normal cruise, try adjusting the VAFM 3-4 clicks in the lean direction (adjust in the direction that tightens the spring). That will tell the ECU that less air is coming into the engine, and open loop it will lean out the mixture accordingly. If the voltage is consistently above 2.5 volts, try adjusting the VAFM in the rich direction.
You can also monitor the O2 output directly on the diag connector on the Ox1 terminal. Make sure you use a multimeter with a high input impedance (> 1 Megohm. Most digital multimeters are 10Megohm, so are fine. Most cheap analog meters are about 20K ohms, so will load the O2 sensor down and prevent it from operating.) During normal cruise Ox1 should be switching between 0 and 1 volt at about once/second. If it's stuck one direction or the other, the ECU has run out of control range and cannot get the mixture to stoichiometric. (0V => lean, 1V => rich.)
One other reason to adjust the VAFM is if you consistently operate at altitudes of 5000 feet or above (ie, Denver). The VAFM is a somewhat crude device, and it doesn't track altitude accurately. As altitude goes up, it will give a false indication (in the plus direction) of how much air is going into the engine. I found I could center up the VF1 voltage by adjusting the VAFM 4 clicks lean, and that fuel economy and engine performance increased slightly as a result.
Possibly more than you wanted to know, but as an engineer, this sort of control loop stuff fascinates me.
The ECU runs in two modes, open loop and closed loop. Open loop occurs primarily under three conditions. (1) cold engine (2) closed throttle (3) wide open throttle. Closed loop operation occurs under most normal driving conditions.
In open loop, the ECU takes data from various sensors (primarily VAFM, ECT, TPS, and RPM) and estimates proper timing and injector pulse width based on a big lookup table to get a mixture setting that's close to optimum. Generally it shoots for stoichiometric except in the case of wide-open throttle, in which case it enriches the mixture somewhat for better power and more resistance to knocking.
In closed loop operation, the ECU makes its best estimate as above, but then takes input from the O2 sensor to fine-tune the mixture to stoichiometric. This is necessary not so much for engine performance, but to optimize the operation of the "3-way" catalytic converter for minimum emissions. The narrow-band O2 sensor acts like a switch, putting out 0 volt when the mixture is even slightly lean, and 1V when the mixture is slightly rich. The ECU control loop adjusts the mixture about once/second such that the O2 sensor output continually oscillates between 0V and 1V when things are operating properly. That ensures that the average mixture is stoichiometric.
The ECU puts out a voltage on the VF1 terminal in the diag connector which indicates how much the open loop estimate was in error compared to the O2 sensor. If VF1 measures 2.5 volts, the open loop estimate was right on. If the voltage is below 2.5V, the open loop estimate was biased toward rich, and the O2 sensor is telling the ECU to move the mixture leaner. If the voltage is above 2.5V, the open loop estimate is biased toward lean, and the O2 sensor is asking for a richer mixture.
If VF1 is pegged at either 0V or 5 volts during what should be closed-loop operation, the ECU has run out of control range and can no longer bring the mixture back to stoichiometric based on the O2 sensor output. The ECU has about +/- 20% mixture control range from its open loop estimate before it runs into the limits. This limit is there in part so that a defective O2 sensor doesn't render the engine completely inoperative.
So, what happens when you modify the VAFM or the injector size. Effectively, the lookup table that the ECU uses to initially estimate the mixture is no longer quite correct, so in open loop operation it will not get as close to the right mixture as it should. It may or may not have enough control range to still get back to stoichiometric based on the O2 sensor output. You can help out the ECU by adjusting the VAFM so it uses a slightly different part of the lookup table which more closely represents the new reality.
You don't really need a wide-band sensor and meter to adjust things. You can tweak things by putting a meter on the VF1 terminal and driving around. Once the engine warms up, check the voltage. If it is consistently below 2.5 volts in normal cruise, try adjusting the VAFM 3-4 clicks in the lean direction (adjust in the direction that tightens the spring). That will tell the ECU that less air is coming into the engine, and open loop it will lean out the mixture accordingly. If the voltage is consistently above 2.5 volts, try adjusting the VAFM in the rich direction.
You can also monitor the O2 output directly on the diag connector on the Ox1 terminal. Make sure you use a multimeter with a high input impedance (> 1 Megohm. Most digital multimeters are 10Megohm, so are fine. Most cheap analog meters are about 20K ohms, so will load the O2 sensor down and prevent it from operating.) During normal cruise Ox1 should be switching between 0 and 1 volt at about once/second. If it's stuck one direction or the other, the ECU has run out of control range and cannot get the mixture to stoichiometric. (0V => lean, 1V => rich.)
One other reason to adjust the VAFM is if you consistently operate at altitudes of 5000 feet or above (ie, Denver). The VAFM is a somewhat crude device, and it doesn't track altitude accurately. As altitude goes up, it will give a false indication (in the plus direction) of how much air is going into the engine. I found I could center up the VF1 voltage by adjusting the VAFM 4 clicks lean, and that fuel economy and engine performance increased slightly as a result.
Possibly more than you wanted to know, but as an engineer, this sort of control loop stuff fascinates me.
02-24-2015, 08:14 AM
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This is what I need to know thank you. I don't need a wideband to get my ratio right. I can just test the voltage on the one connector and see if it's running lean or rich.
02-24-2015, 10:25 AM
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Keep in mind that "running rich or running lean" in closed loop means the ECU has run out of adjustment range. When that happens, the ECU isn't shy: it throws a code. So if you don't have a code, the ECU thinks it's got you covered, and you're NOT running rich or lean.
The adjustments RJR is talking about only affect open loop; engine cold, WOT, and idle. If you have driveability problems when the engine is warm, your problem lies elsewhere. But if open loop IS your problem, as RJR points out, the ECU helps you here as well. The ECU "remembers" what the VAF said about air flow during open loop, and uses that for the "stored fuel trim" you can read on VF1. That stored fuel trim is where the ECU starts the next time you're in open loop.
You don't need to do anything about it, but if you're an engineer like RJR you can tweak the VAF to get the stored fuel trim back to the middle.
The adjustments RJR is talking about only affect open loop; engine cold, WOT, and idle. If you have driveability problems when the engine is warm, your problem lies elsewhere. But if open loop IS your problem, as RJR points out, the ECU helps you here as well. The ECU "remembers" what the VAF said about air flow during open loop, and uses that for the "stored fuel trim" you can read on VF1. That stored fuel trim is where the ECU starts the next time you're in open loop.
You don't need to do anything about it, but if you're an engineer like RJR you can tweak the VAF to get the stored fuel trim back to the middle.
02-24-2015, 10:40 AM
#16
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I have been having issues with it after sitting at idle for over 15 mins it wants to lean itself out and it takes a couple miles to regain all my power back. It's worse if I start it in the morning when it's cold out to let it warm up. If I just get in and drive it does fine. I just put a new coolant temp sensor on it and it helped a little but didn't fix the issue. That's why I am wanting to know for sure when it does it what my fuel air ratio is doing and what could be causing it.
02-24-2015, 10:40 AM
#17
Scope is absolutely correct in his description of how things work (as usual). Here's a bit more detail.
The ECU runs in two modes, open loop and closed loop. Open loop occurs primarily under three conditions. (1) cold engine (2) closed throttle (3) wide open throttle. Closed loop operation occurs under most normal driving conditions.
In open loop, the ECU takes data from various sensors (primarily VAFM, ECT, TPS, and RPM) and estimates proper timing and injector pulse width based on a big lookup table to get a mixture setting that's close to optimum. Generally it shoots for stoichiometric except in the case of wide-open throttle, in which case it enriches the mixture somewhat for better power and more resistance to knocking.
In closed loop operation, the ECU makes its best estimate as above, but then takes input from the O2 sensor to fine-tune the mixture to stoichiometric. This is necessary not so much for engine performance, but to optimize the operation of the "3-way" catalytic converter for minimum emissions. The narrow-band O2 sensor acts like a switch, putting out 0 volt when the mixture is even slightly lean, and 1V when the mixture is slightly rich. The ECU control loop adjusts the mixture about once/second such that the O2 sensor output continually oscillates between 0V and 1V when things are operating properly. That ensures that the average mixture is stoichiometric.
The ECU puts out a voltage on the VF1 terminal in the diag connector which indicates how much the open loop estimate was in error compared to the O2 sensor. If VF1 measures 2.5 volts, the open loop estimate was right on. If the voltage is below 2.5V, the open loop estimate was biased toward rich, and the O2 sensor is telling the ECU to move the mixture leaner. If the voltage is above 2.5V, the open loop estimate is biased toward lean, and the O2 sensor is asking for a richer mixture.
If VF1 is pegged at either 0V or 5 volts during what should be closed-loop operation, the ECU has run out of control range and can no longer bring the mixture back to stoichiometric based on the O2 sensor output. The ECU has about +/- 20% mixture control range from its open loop estimate before it runs into the limits. This limit is there in part so that a defective O2 sensor doesn't render the engine completely inoperative.
So, what happens when you modify the VAFM or the injector size. Effectively, the lookup table that the ECU uses to initially estimate the mixture is no longer quite correct, so in open loop operation it will not get as close to the right mixture as it should. It may or may not have enough control range to still get back to stoichiometric based on the O2 sensor output. You can help out the ECU by adjusting the VAFM so it uses a slightly different part of the lookup table which more closely represents the new reality.
You don't really need a wide-band sensor and meter to adjust things. You can tweak things by putting a meter on the VF1 terminal and driving around. Once the engine warms up, check the voltage. If it is consistently below 2.5 volts in normal cruise, try adjusting the VAFM 3-4 clicks in the lean direction (adjust in the direction that tightens the spring). That will tell the ECU that less air is coming into the engine, and open loop it will lean out the mixture accordingly. If the voltage is consistently above 2.5 volts, try adjusting the VAFM in the rich direction.
You can also monitor the O2 output directly on the diag connector on the Ox1 terminal. Make sure you use a multimeter with a high input impedance (> 1 Megohm. Most digital multimeters are 10Megohm, so are fine. Most cheap analog meters are about 20K ohms, so will load the O2 sensor down and prevent it from operating.) During normal cruise Ox1 should be switching between 0 and 1 volt at about once/second. If it's stuck one direction or the other, the ECU has run out of control range and cannot get the mixture to stoichiometric. (0V => lean, 1V => rich.)
One other reason to adjust the VAFM is if you consistently operate at altitudes of 5000 feet or above (ie, Denver). The VAFM is a somewhat crude device, and it doesn't track altitude accurately. As altitude goes up, it will give a false indication (in the plus direction) of how much air is going into the engine. I found I could center up the VF1 voltage by adjusting the VAFM 4 clicks lean, and that fuel economy and engine performance increased slightly as a result.
Possibly more than you wanted to know, but as an engineer, this sort of control loop stuff fascinates me.
The ECU runs in two modes, open loop and closed loop. Open loop occurs primarily under three conditions. (1) cold engine (2) closed throttle (3) wide open throttle. Closed loop operation occurs under most normal driving conditions.
In open loop, the ECU takes data from various sensors (primarily VAFM, ECT, TPS, and RPM) and estimates proper timing and injector pulse width based on a big lookup table to get a mixture setting that's close to optimum. Generally it shoots for stoichiometric except in the case of wide-open throttle, in which case it enriches the mixture somewhat for better power and more resistance to knocking.
In closed loop operation, the ECU makes its best estimate as above, but then takes input from the O2 sensor to fine-tune the mixture to stoichiometric. This is necessary not so much for engine performance, but to optimize the operation of the "3-way" catalytic converter for minimum emissions. The narrow-band O2 sensor acts like a switch, putting out 0 volt when the mixture is even slightly lean, and 1V when the mixture is slightly rich. The ECU control loop adjusts the mixture about once/second such that the O2 sensor output continually oscillates between 0V and 1V when things are operating properly. That ensures that the average mixture is stoichiometric.
The ECU puts out a voltage on the VF1 terminal in the diag connector which indicates how much the open loop estimate was in error compared to the O2 sensor. If VF1 measures 2.5 volts, the open loop estimate was right on. If the voltage is below 2.5V, the open loop estimate was biased toward rich, and the O2 sensor is telling the ECU to move the mixture leaner. If the voltage is above 2.5V, the open loop estimate is biased toward lean, and the O2 sensor is asking for a richer mixture.
If VF1 is pegged at either 0V or 5 volts during what should be closed-loop operation, the ECU has run out of control range and can no longer bring the mixture back to stoichiometric based on the O2 sensor output. The ECU has about +/- 20% mixture control range from its open loop estimate before it runs into the limits. This limit is there in part so that a defective O2 sensor doesn't render the engine completely inoperative.
So, what happens when you modify the VAFM or the injector size. Effectively, the lookup table that the ECU uses to initially estimate the mixture is no longer quite correct, so in open loop operation it will not get as close to the right mixture as it should. It may or may not have enough control range to still get back to stoichiometric based on the O2 sensor output. You can help out the ECU by adjusting the VAFM so it uses a slightly different part of the lookup table which more closely represents the new reality.
You don't really need a wide-band sensor and meter to adjust things. You can tweak things by putting a meter on the VF1 terminal and driving around. Once the engine warms up, check the voltage. If it is consistently below 2.5 volts in normal cruise, try adjusting the VAFM 3-4 clicks in the lean direction (adjust in the direction that tightens the spring). That will tell the ECU that less air is coming into the engine, and open loop it will lean out the mixture accordingly. If the voltage is consistently above 2.5 volts, try adjusting the VAFM in the rich direction.
You can also monitor the O2 output directly on the diag connector on the Ox1 terminal. Make sure you use a multimeter with a high input impedance (> 1 Megohm. Most digital multimeters are 10Megohm, so are fine. Most cheap analog meters are about 20K ohms, so will load the O2 sensor down and prevent it from operating.) During normal cruise Ox1 should be switching between 0 and 1 volt at about once/second. If it's stuck one direction or the other, the ECU has run out of control range and cannot get the mixture to stoichiometric. (0V => lean, 1V => rich.)
One other reason to adjust the VAFM is if you consistently operate at altitudes of 5000 feet or above (ie, Denver). The VAFM is a somewhat crude device, and it doesn't track altitude accurately. As altitude goes up, it will give a false indication (in the plus direction) of how much air is going into the engine. I found I could center up the VF1 voltage by adjusting the VAFM 4 clicks lean, and that fuel economy and engine performance increased slightly as a result.
Possibly more than you wanted to know, but as an engineer, this sort of control loop stuff fascinates me.
02-24-2015, 12:29 PM
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The adjustments RJR is talking about only affect open loop; engine cold, WOT, and idle. If you have driveability problems when the engine is warm, your problem lies elsewhere. But if open loop IS your problem, as RJR points out, the ECU helps you here as well. The ECU "remembers" what the VAF said about air flow during open loop, and uses that for the "stored fuel trim" you can read on VF1. That stored fuel trim is where the ECU starts the next time you're in open loop.
You don't need to do anything about it, but if you're an engineer like RJR you can tweak the VAF to get the stored fuel trim back to the middle.
You don't need to do anything about it, but if you're an engineer like RJR you can tweak the VAF to get the stored fuel trim back to the middle.
02-24-2015, 12:46 PM
#19
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The first mile I drive it I can feel the power drop then come back and back and forth. once it's close to operating temp it straightens itseft out and doesn't pulse back and forth. It's not like a sputter it just like a decrease in hp then regain in hp in the matter of two sec.
02-24-2015, 01:03 PM
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Doesn't sound like something that adjusting the VAFM would necessarily fix. More likely an unreliable signal from the ECT, such that the ECU isn't getting an accurate, stable temperature reading when the engine is cold. Could also be a bubble in the coolant.
You can check the ECT as it's working by backprobing the connector and watching the voltage as the engine heats up. It should start out around 5 volts with a cold engine and steadily decrease to a couple of volts as the engine warms up. If it jumps around in the process you know it's giving the ECU bad data.
TPS is another possiblity. Put an ohm meter on it and look for dead spots or jumps as you go through the full throttle travel.
You can check the ECT as it's working by backprobing the connector and watching the voltage as the engine heats up. It should start out around 5 volts with a cold engine and steadily decrease to a couple of volts as the engine warms up. If it jumps around in the process you know it's giving the ECU bad data.
TPS is another possiblity. Put an ohm meter on it and look for dead spots or jumps as you go through the full throttle travel.
