I have the safc II and at idle my vf is 4.7. Is this normal. I read where ov means rich and 5v means lean of course learned value. I have lex afm and 550 with stock regulator. I took the vac. line off of the regulator to try that but no results. The tsrm says fuel pressure is 33-40 with no vac. Is my stock fuel pump weak. I have no way right now to check the fuel pressure. I am planning to get the afpr with a guage on it. I was wondering if anybody has experienced the same issue.
VF signal
- Thread starter 89supracrazy
- Start date
4.7v (equivalent to 5v) is not normal for operating temp idle. See:
Turn your Lex bypass screw all the way in.
Turn your Lex bypass screw all the way in.
I do have the screw in as far as it will go. I dont have the supersonic screw for the lexus. With the orginal screw that comes with the lexus afm I still have about half unmetered air flowing threw. Do I need to get the supersonic screw or just invest in an afpr to bring it in range.
Check it from the diagnostic port like in the pic to see if the safc is showing it correctly.
Even without the long screw you should still be very rich with a lex/550 setup...
Even without the long screw you should still be very rich with a lex/550 setup...
OK I will tomorrow. I thought I checked it before I got the safc and it read 3.2volts not for sure. I will recheck it. Is the safc not to accurate. Just curious.
Ok I checked the vf signal in the diagnostic block and it is the same as safc. What could cause this to read 4.7 volts at idle. I have to put my safc to +30 to get it to 2.1 volts. I read that the lex and the 550 would run rich but how can it when I have alot of unmetered air. I dont have the supersonic screw but I do have the factory screw in as far as it will go. Does this explain why I have to set the safc to +30 to compensate for more air. I also noticed that every time I let off the throttle that it reads 0 volts for a few seconds.
There's lots of things that can cause high Vf but worrying about it at idle is a bit anal. What is it at 2500 rpm? And it's supposed to read zero when you let off...
I went back out to check and when I first cranked it with the safc set to 0 volts it read 3.4 volts. When I move the safc to -5 it went to 4.7volts. I moved the safc to 0 volts again and it stayed at 4.7 volts all threw the rpms, even at 2500 rmps. Is the oxygen sensor sending false readings.
As I said it could be lots of things. The system is adding fuel to compensate for an imbalance. It doesn't necessarily mean the mixture is lean although it could be. There's not much harm in this other than it may slightly effect fuel economy. First clear the learned value and see what happens. Then measure the O2 sensor's average voltage. If you can't do that try blocking more of the AFM's bypass chamber. And leave the safc set to zero while troubleshooting.
Some possible causes for the problem:
1) Vacuum leak
2) low fuel pressure
3) Partially clogged injector(s)
4) Shifted AFM signal
5) Coolant temp sensor shift low
6) Intake air sensor shifted high
The usual cause is a vacuum leak. Get it smoked. I have yet to work on a 7M that didn't have leaks. Then again you've modified the system so who knows.
The O2 sensor shouldn't be involved because learned value is calculated before feedback compensation is performed...
Some possible causes for the problem:
1) Vacuum leak
2) low fuel pressure
3) Partially clogged injector(s)
4) Shifted AFM signal
5) Coolant temp sensor shift low
6) Intake air sensor shifted high
The usual cause is a vacuum leak. Get it smoked. I have yet to work on a 7M that didn't have leaks. Then again you've modified the system so who knows.
The O2 sensor shouldn't be involved because learned value is calculated before feedback compensation is performed...
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jetjock;1535048 said:
what? why do you think that the computer adjusts VF? its to keep the oxygen sensor and catalyst running efficiently (this is the entire purpose of OBD systems). If you have a o2 issue VF will definitely be out of wack.
the o2 is the feedback in a feedback system therefore very important.
I'm well aware of the NB sensor's purpose and that a lack of feedback will cause problems with Vf however it's very unlikely to be causing this particular symptom. That's why I said "shouldn't". As for how the learned value is calculated perhaps you should review Toyota's documentation on the system.
Not easy to find these days because it's all out of print. I collected it during the 22 years I owned the car and much of it wasn't available to the general public. About all I can suggest is to keep an eye on Ebay.
I suspect we're both talking about the same thing but in different ways and would end up agreeing more than disagreeing. For example you'll note in my reply I did tell him to check average sensor voltage. That said fuel trim on his car doesn't work quite the same way as it does on OBD-II.
I suspect we're both talking about the same thing but in different ways and would end up agreeing more than disagreeing. For example you'll note in my reply I did tell him to check average sensor voltage. That said fuel trim on his car doesn't work quite the same way as it does on OBD-II.
I thought I was doing that by being here. For example you may be surprised to know learned value has the greatest effect on the engine during open loop...
89supracrazy;1533813 said:
Lets go back to this. Are you making any gain adjustments at idle on the safc? You're fighting the TCCS if you are. You should not be making any adjustments below 3000~3500 RPM anyway.
You need to zero out any adjustments you are making with the safc and make sure the tccs is happy.
What does your wideband tell you?
What is your cruising speed VF?
mkiiichip;1535105 said:
To use the term loosely, fuel trim is adusting to the car and its driver. Both short and long term. The oxygen feedback as you have correctly stated is for the cat. 14.7:1 is not where the car runs best, it is where the cat runs best. You are right on track. Short term from the oxygen helps write the long term. Or more accurately is a correction.
mkiiichip;1535130 said:
My old courses are a long way from here, as in home. I have some even older PDF files.
Toyota said:
I dont have a wideband yet. I am going to order the zt2- zr2 from driftmotion. I am going by just the vf signal only and I know the computer is compensating for the fuel but I am concerned with it. When I am going down the road cruising it is about 3.4 volts. I am the type of person that whatever the specs. should be that is what I want nothing less. I might be jumping the gun because I dont have a wideband. I am just trying different things just to see if I can steady the vf signal.
Ok not to get off subject but I wanted to check my timing today and I was bumping my motor over trying to find my mark on my pulley. When I went to start it my car would not start. So I unplugged my main relay and turned it over a few times to see if it was flooded. I installed the main relay and it hit one time but still did not start and even tried pushing the pedal to the floor with no results. I thought if it was flooded I'll try to unplug the resistor pack going to the injectors. It fired right up and Idle a few seconds and then it died. This is all hot start. It smoked really bad, white I think. I plugged the resistor pack back up and it started right up but it continued to smoke for about 2 minutes. It is doing the same thing on deceleration. I believe my vf reading is due to much bypass air because when I get about 10 percent throttle the vf goes down to 3.2 volts. Not 100 percent positive though.