Please help before I drive my FI SC400 into a lake and leave it for dead!
03-07-08, 12:25 PM
#48
Ok, somewhat of an update.
A guy over at full throttle (maftpro tech support forums) told me to moniter the VF readings. The VF readings are the OBD1 version of fuel trim. On an OBD2 vehicle (Toyota's anyway) fuel trim is read as a percentage, I think most newer Toyota's read from -32% to +32%. A negative number indicating that the engine is running rich and the ECU is reducing fuel.
With OBD1, the ECU uses 5 measurments for closed loop. Very lean, lean, perfect, rich, and very rich. In the case of a 95 SC400, there are two VF terminals in the data link connector under the hood, VF1 and VF2. VF1 is bank 1, driver's side, VF2 is bank 2, passenger side. The VF is determined by feed back from the O2 sensors. And on another note, the ECU can control fueling for each bank idependantly. Bank 1 can be running in open loop and bank 2 can be running in closed loop. This is part of my problem, I think, I haven't confirmed quite yet.
So, what I found while monitoring the VF signals....this is where it starts to get a bit confusing. There are 5 steped voltages that can be seen on the VF terminals for closed loop operation. If I'm not mistaken, they go very rich 5volts +-, rich 3.75 volts +-, perfect (14.7) 2.5 volts +- lean 1.25 +-, and very lean close to 0 volts but not zero volts. Open loop is zero volts. Note, I think I figured out that my AFR doen't change between a hot and cold start, it changes between the first start after resetting the memory and the second start after resetting the memory. When monitoring my VF1 (bank 1) with the O2 sensor disconnected on the first start, I read 0 volts. The voltage doesn't change from zero. On the second start, it reads 0 volts for about 30 seconds and then goes to 2 volts and doesn't ever change. When monitoring VF2 (bank 2) with the sensor unplugged, it does the same thing. When I plug the sensor in, it works like normal, varying between 0 and 5 volts.
So this is what I think is happening.....An O2 sensor fault is a two trip detection logic failure. When the memory is reset and the car is started, the ECU sees that the O2 is not reading and keeps the bank in open loop. On the next start up, the ECU sees that the O2 is still not reading and throws a check engine light. Also, it puts the VF to two volts (which I think is lean, meaning its adding fuel) as a fail safe, better rich than lean.
Now, if this is the case, then this has been happening for a while, I just haven't noticed it due to the fact that the MAFTPro can be set to automatically adjust the idle and cruise AFR. I have no idea (yet) if this has anything to do with my lean condition with load. With pretty much any foot into the pedal, the VF goes to 0, which is open loop, so I don't think it's the reason I'm going lean. This also means that since I removed the bank 1 O2 sensor to install the wideband, I've been running in open loop / fail safe on bank 1, while being in closed loop on bank 2. AND...with the MAFTPro adjusting fuel automatically at idle and cruise, the ECU is likely getting pissed off trying to keep the bank 2 fuel trim correct since in theory, bank 2 is running leaner than bank 1 and the MAFTPro is using my wideband signal from bank 1 to do the automatic adjustments.
Sorry if this is all confusing, if it makes anyone feel any better, I'm a bit confused too. From what I'm told, VF readings are nothing new to the Supra guys. I've been working on Toyota's for 7 years now, but don't really know too much about OBD1 diagnostics. Most of the stuff dealers work on these days is OBD2.
So what I'm going to try and do...I'm going to bridge the oxy1 and oxy2 terminals at the data link connector under the hood to see if anything changes. By doing this (I have studied the wiring diagram to be sure I won't blow anything up) my passenger side O2 sensor will be supplying a signal for both O2 sensors to the ECU. In theory, this should work fine untill I can find a way to add a seperate bung for the wideband.
As far as my lean with boost problem. It's better than it was. The different MAF didn't really seem to make any difference. Replacing the engine coolant temp sensor actually helped quite a bit. And even though a different MAF didn't help, it seems to be better when running in speed density. I may install the 315's this weekend, if I fix the above talked about problem.
I am also going to try and block of the EGR port on the back of the intake manifold, this should drastically reduce manifold heat. I am also considering getting rid of all the coolant lines running into the manifold. The line that goes to the EGR (already blocked of and bypassed) to the IAC and to the throttle body.
Keep an eye out for some pics on my original thread. Maybe some vids if I manange to get the car right.
Sorry for such a long read.
KC
A guy over at full throttle (maftpro tech support forums) told me to moniter the VF readings. The VF readings are the OBD1 version of fuel trim. On an OBD2 vehicle (Toyota's anyway) fuel trim is read as a percentage, I think most newer Toyota's read from -32% to +32%. A negative number indicating that the engine is running rich and the ECU is reducing fuel.
With OBD1, the ECU uses 5 measurments for closed loop. Very lean, lean, perfect, rich, and very rich. In the case of a 95 SC400, there are two VF terminals in the data link connector under the hood, VF1 and VF2. VF1 is bank 1, driver's side, VF2 is bank 2, passenger side. The VF is determined by feed back from the O2 sensors. And on another note, the ECU can control fueling for each bank idependantly. Bank 1 can be running in open loop and bank 2 can be running in closed loop. This is part of my problem, I think, I haven't confirmed quite yet.
So, what I found while monitoring the VF signals....this is where it starts to get a bit confusing. There are 5 steped voltages that can be seen on the VF terminals for closed loop operation. If I'm not mistaken, they go very rich 5volts +-, rich 3.75 volts +-, perfect (14.7) 2.5 volts +- lean 1.25 +-, and very lean close to 0 volts but not zero volts. Open loop is zero volts. Note, I think I figured out that my AFR doen't change between a hot and cold start, it changes between the first start after resetting the memory and the second start after resetting the memory. When monitoring my VF1 (bank 1) with the O2 sensor disconnected on the first start, I read 0 volts. The voltage doesn't change from zero. On the second start, it reads 0 volts for about 30 seconds and then goes to 2 volts and doesn't ever change. When monitoring VF2 (bank 2) with the sensor unplugged, it does the same thing. When I plug the sensor in, it works like normal, varying between 0 and 5 volts.
So this is what I think is happening.....An O2 sensor fault is a two trip detection logic failure. When the memory is reset and the car is started, the ECU sees that the O2 is not reading and keeps the bank in open loop. On the next start up, the ECU sees that the O2 is still not reading and throws a check engine light. Also, it puts the VF to two volts (which I think is lean, meaning its adding fuel) as a fail safe, better rich than lean.
Now, if this is the case, then this has been happening for a while, I just haven't noticed it due to the fact that the MAFTPro can be set to automatically adjust the idle and cruise AFR. I have no idea (yet) if this has anything to do with my lean condition with load. With pretty much any foot into the pedal, the VF goes to 0, which is open loop, so I don't think it's the reason I'm going lean. This also means that since I removed the bank 1 O2 sensor to install the wideband, I've been running in open loop / fail safe on bank 1, while being in closed loop on bank 2. AND...with the MAFTPro adjusting fuel automatically at idle and cruise, the ECU is likely getting pissed off trying to keep the bank 2 fuel trim correct since in theory, bank 2 is running leaner than bank 1 and the MAFTPro is using my wideband signal from bank 1 to do the automatic adjustments.
Sorry if this is all confusing, if it makes anyone feel any better, I'm a bit confused too. From what I'm told, VF readings are nothing new to the Supra guys. I've been working on Toyota's for 7 years now, but don't really know too much about OBD1 diagnostics. Most of the stuff dealers work on these days is OBD2.
So what I'm going to try and do...I'm going to bridge the oxy1 and oxy2 terminals at the data link connector under the hood to see if anything changes. By doing this (I have studied the wiring diagram to be sure I won't blow anything up) my passenger side O2 sensor will be supplying a signal for both O2 sensors to the ECU. In theory, this should work fine untill I can find a way to add a seperate bung for the wideband.
As far as my lean with boost problem. It's better than it was. The different MAF didn't really seem to make any difference. Replacing the engine coolant temp sensor actually helped quite a bit. And even though a different MAF didn't help, it seems to be better when running in speed density. I may install the 315's this weekend, if I fix the above talked about problem.
I am also going to try and block of the EGR port on the back of the intake manifold, this should drastically reduce manifold heat. I am also considering getting rid of all the coolant lines running into the manifold. The line that goes to the EGR (already blocked of and bypassed) to the IAC and to the throttle body.
Keep an eye out for some pics on my original thread. Maybe some vids if I manange to get the car right.
Sorry for such a long read.
KC
03-07-08, 02:41 PM
#49
Quick update.
Bridging the oxy1 and oxy2 terminal at the data connector seems to have fixed the one problem.
I am now seeing the VF1 and 2 voltages vary from 1 volt to .5 volt. My idle AFR was staying at 14.7ish to 1.
I think I may have mistated on the previous post. I think lower voltage is rich (taking out fuel) and high voltage is lean (adding fuel). So, in my case, .5 volts is is probably very rich and 1 volt is rich (taking out fuel). Before I was seeing 2 volts when my AFR was going rich, which must either be perfect (14.7 to 1) or lean (adding fuel).
Now, next problem. My idle is a bit rough with some missing. If I unplug the MAF, the idle smooths out and the AFR goes to 12.5 to 1. From this I can determine that my base AFR without any adjustment from the MAFTPro is 12.5ish to 1. This may be because of the high flow fuel pump. My fuel pressure is a tad bit higher than it should be by the book.
Why does the engine smooth out? The only two possibilities I can think of are 1. both of the MAF's I have in my possesion are bad (I tried it with both) or 2. I have a vac leak somewhere. I can't see having a vac leak because with the MAF plugged in, the ECU is taking out fuel to maintain the AFR at 14.7. If I had a leak, I would think that the ECU would be adding fuel to compensate for the unmetered air.
Also, when I got the second MAF, I intalled it and went for a drive. I got back home and popped the hood. Much to my absolute amazement, the top cover of the MAF was very close to popping off. I have know idea why I have such bad luck with these stupid things. I envy you guys with the hot wire MAF.
I'm going to check for leaks, if I can't find anything, I'll have to assume that I have two bad MAF's. In which case, I'll make a real attempt to tune the Pro in speed density mode so I can get rid of the stupid thing.
KC
Bridging the oxy1 and oxy2 terminal at the data connector seems to have fixed the one problem.
I am now seeing the VF1 and 2 voltages vary from 1 volt to .5 volt. My idle AFR was staying at 14.7ish to 1.
I think I may have mistated on the previous post. I think lower voltage is rich (taking out fuel) and high voltage is lean (adding fuel). So, in my case, .5 volts is is probably very rich and 1 volt is rich (taking out fuel). Before I was seeing 2 volts when my AFR was going rich, which must either be perfect (14.7 to 1) or lean (adding fuel).
Now, next problem. My idle is a bit rough with some missing. If I unplug the MAF, the idle smooths out and the AFR goes to 12.5 to 1. From this I can determine that my base AFR without any adjustment from the MAFTPro is 12.5ish to 1. This may be because of the high flow fuel pump. My fuel pressure is a tad bit higher than it should be by the book.
Why does the engine smooth out? The only two possibilities I can think of are 1. both of the MAF's I have in my possesion are bad (I tried it with both) or 2. I have a vac leak somewhere. I can't see having a vac leak because with the MAF plugged in, the ECU is taking out fuel to maintain the AFR at 14.7. If I had a leak, I would think that the ECU would be adding fuel to compensate for the unmetered air.
Also, when I got the second MAF, I intalled it and went for a drive. I got back home and popped the hood. Much to my absolute amazement, the top cover of the MAF was very close to popping off. I have know idea why I have such bad luck with these stupid things. I envy you guys with the hot wire MAF.
I'm going to check for leaks, if I can't find anything, I'll have to assume that I have two bad MAF's. In which case, I'll make a real attempt to tune the Pro in speed density mode so I can get rid of the stupid thing.
KC
03-07-08, 09:58 PM
#50
Another quick update.
So I think I have the hot cold AFR thing figured out. I decided to do a quick leak check before going for a drive. I found something very interesting. The injector seals are leaking under pressure. I discovered this while doing my plastic bag on the SC intake / blow air into the manifold and spray soapy water leak test.
So....since I need to change the o-rings (which I had already purchased), I've decided against my better judgement, to put in the 315's while I'm at it. I say against my better judgement only because I was hoping to make sure my other problems were fixed first, oh well.
KC
So I think I have the hot cold AFR thing figured out. I decided to do a quick leak check before going for a drive. I found something very interesting. The injector seals are leaking under pressure. I discovered this while doing my plastic bag on the SC intake / blow air into the manifold and spray soapy water leak test.
So....since I need to change the o-rings (which I had already purchased), I've decided against my better judgement, to put in the 315's while I'm at it. I say against my better judgement only because I was hoping to make sure my other problems were fixed first, oh well.
KC
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