cpljenkins01

I have a 90 pickup with the 3vze. I have been noticing that from the time I start my truck till it gets to operating temperature my fuel mileage is horrible. I also noticed here resently that only sometimes that it has a hard time starting when its not completely cooled down. The other thing I noticed it doing is when I am at steady acceleration I can feel it lose power then gain it right back not a lot of power just enough to notice it but it only does it when its believe operating temperature once it has warmed up it runs great. The only thing I have done is put flamethrower injectors in about 2 months ago.

RAD4Runner

What was broken that you were trying to fix with the FT injectors?
Did you have the problem before you installed the Flamethrower injectors?
If not, then maybe the FT injectors ARE your problem.

Cold start injector only gets power to open and to spray fuel while you have ignition switch in Start (cranking) position. IF it keeps on spraying even without power to it, maybe it's stuck open?

RJR

You might want to check the ECT (engine coolant temperature) sensor. It sounds like it might be indicating a lower engine temperature to the ECU than is actually the case. That will delay when the ECU goes to a "fully warmed up" status, and it will operate in a richer mode until that point. That would give you results similar to what you're seeing.

cpljenkins01

I have a narrowband o2 and gauge but it dont tell me exactly the true reading and it takes a while to warm up the o2 sensor so by the time it gets warm so is my truck and it goes back to running good.

hiluxhack

I'm simple minded so I do simple things first. Did you check the air filter?

cpljenkins01

I keep the filter clean it has s cold air intake on it.

RJR

The other not-unlikely cause is that the flamethrowers may put out somewhat more fuel than the stock injectors. When the engine is cold the ECU runs open loop, so it's using its best guess for injector timing, which with the new injectors likely results in rich running. After the engine gets warm, the ECU goes into closed loop mode and can then use the O2 sensor output to tweak the mixture correctly.

You can tell how much the ECU is having to correct for the injectors by warming up the engine fully, and then putting a voltmeter on the VF1 terminal of the diag port. Run the engine above idle, perhaps at 1500-2000 rpm and observe the voltage. Nominal is 2.5 volts. If it is below 2.5 volts, it tells you the ECU is having to reduce fuel to keep it from running rich. If it's above 2.5, the ECU is working to increase fuel to correct for a lean condition. I suspect yours will probably run 0 to 1.25 volts.

You can also check out the O2 sensor by shorting TE1 to E1 in the diag port and then restarting the engine. Again, with the engine warmed up and running about 1500 rpm, observe the voltage on VF1. It should be switching back and forth between 0 and 5V around once/second. If it's stuck at 0V, the O2 sensor is telling the ECU that the engine is running lean. If it's stuck at 5V, the engine is running rich.

If you can make both of those measurements and report back, we can move a little further from speculation and a little closer to diagnosis.

cpljenkins01

Ok I will let you know.

cpljenkins01

Well I had to check it by myself and couldn't set the idle right so I tested it at 1,000 rpm and it was reading 1.15 volts

RJR

That says the open-loop condition of the engine is somewhat rich. You'll probably want to tweak the VAFM to get that signal closer to 2.5 volts. That may not be all of your issue, but would be a step in the right direction.

Check out this link for how to tweak the VAFM. It's not hard, just be careful and keep dirt out of it. You can reseal it with duct tape until you get it where you want it, and then you can permanently reseal it with RTV.
http://www.4x4wire.com/toyota/minutemods/afm/
Three or four clicks in the lean direction should get you pretty close. Just make sure you mark it before you move it so you can get back to original setting if something goes wrong.

I'm not 100% sure the CW/CCW directions in the article are correct for your VAFM. What I can say for sure is that you want to turn the cog so as to tighten the spring in order to make the mixture more lean. That makes the vane harder to move, so it reports less air flow to the ECU. The ECU compensates by reducing the fuel flow, giving you a leaner mixture.

cpljenkins01

Ok thank you. I will try it. I have a 7mge vafm right now so I may not have turned it lean enough when I put in on.

cpljenkins01

Does this look right?

RJR

Yes, that looks good. If you still have issues then there is something else going on.

cpljenkins01

Ok thanks