Unplug Idle air control valve and engine dies (2.9L V6), Normal or bad valve?

[RonD]

Yes, O2 sensors can't work until they get above 650degF, so need to heat up first, but only maybe 3 to 5 minutes on cold start, engine temp can still be at 1/4 on the gauge, not fully warmed up, but CHOKE is still on so engine would still run a bit Rich

Test for O2 is WOT(wide open throttle), after warm up go for a drive at 65mph when starts to cut out, press gas pedal to the floor, WOT
Computer ignores O2 sensor at that time and goes for max power, fuel economy is out the window, lol
If engine starts to run better then yes change O2 sensor
O2 sensors do wear out, they run out of the chemical used to detect oxygen in the exhaust, 150k miles or so, you will see MPG slowly go down as engine runs richer from failing O2


Yes, fuel injectors that sit with fuel in them can get plugged up as the fuel degrades, it changes into a varnish like sludge

 

[PetroleumJunkie412]

Well the FPR only uses vacuum assist at idle, high vacuum, once vacuum is gone, i.e. boost added, its running at 43-45psi pressure, the FPR's max rating, and would hold that pressure until pump couldn't provide that much, lol

When you say you disconnected FPR you mean you blocked the return, right?
Which can be hard on the pump, since its always on and wants to pump the same max volume all the time, which is the point of the FPR being used, its not just for the computer, although having a stable fuel pressure will make calculating AFR much easier, lol, and its why there is vacuum assist on the FPR
Its also there so the pump can run at max volume without too much back pressure, the extra just goes back to the tank

You could do similar to a 1998 and up setup and put return line and FPR between fuel filter and tank, the 3 port filters, but Ford put the FPR in the tank on those assemblies, but no reason you couldn't do that on the return line, outside the tank
Although just having FPR on the engine as it is now would be easier

Not sure why you would need a variable FPR(well more variable than the stock one), unless your pressure is dropping too much at WOT and full boost, but it shouldn't with 340 LPH
Never looked at the diaphragm setup in the FPR so not sure how it reacts to positive pressure, boost, but a check valve on that vacuum line would take that off the table

Adopt me.

 

[PetroleumJunkie412]

When you say you disconnected FPR you mean you blocked the return, right?

Also, no sir, disconnected and blocked vacuum line and let fuel run full flow

 

[wildbill23c]

Yes, O2 sensors can't work until they get above 650degF, so need to heat up first, but only maybe 3 to 5 minutes on cold start, engine temp can still be at 1/4 on the gauge, not fully warmed up, but CHOKE is still on so engine would still run a bit Rich

Test for O2 is WOT(wide open throttle), after warm up go for a drive at 65mph when starts to cut out, press gas pedal to the floor, WOT
Computer ignores O2 sensor at that time and goes for max power, fuel economy is out the window, lol
If engine starts to run better then yes change O2 sensor
O2 sensors do wear out, they run out of the chemical used to detect oxygen in the exhaust, 150k miles or so, you will see MPG slowly go down as engine runs richer from failing O2


Yes, fuel injectors that sit with fuel in them can get plugged up as the fuel degrades, it changes into a varnish like sludge

During a high speed drive that is what's been happening, as soon as it starts to cut out and lose power I'll push the accelerator to the floor, it immediately clears up and starts running normal again....so O2 sensor and fuel injectors sound like a great place to go from here and was thinking along those lines too for a while now...

Thanks again for all the great help and guidance.

 

[RonD]

Also, no sir, disconnected and blocked vacuum line and let fuel run full flow

How did the FPR fail then?
Was fuel leaking into the vacuum hose?

 

[franklin2]

Stay calm, this is a thread jacking.





So... Special circumstance question for you Canadian God, since we're on the subject of injectors, and since WildBill did ask about MS...

With Megasquirt, the Volumetric Efficiency is calculated from Wideband O2 readings; the computer adjusts the VE map to in turn change injector pulsewidths in order to match the AFR table the user programs. Slick system, and gives a very good idea of engine performance at a glance.

My FPR died on me over the summer, so I disconnected it and I let the computer remap around having a significantly higher fuel pressure I could get a new one. This changed my AFR tables significantly, but I noticed no difference in running from the butt dyno or from datalogs.

As of right now, I'm working on the Turbocharger install. I had considered getting a rising rate FPR to make up for the boost pressure affecting fuel regulation, but I'm a cheap b*stard, and havent purchased one yet.

Knowing that I can get the system to make adjustments based on a lack of variable fuel pressure, would it make sense to you to run without a FPR, and to let the system make VE and fueling adjustments knowing I'll have a consistent fuel pressure and volume on a return system?

Have a Kemso 340 LPH pump in the tank ($34 on eBay, and they allow the deletion of the rail pump - really need to write that article as well...). Supplies 340 liters of fuel per hour at 43 psi, so pressure and volume shouldn't be a problem...

My concern is if removing the FPR from the system would cause lean issues; I know I'm going to knock a 93mm hole (or six) in my oil pan eventually, but I'd rather it be from a 3.0 going through my intake, and not from burning lean...

The problem with running very high fuel pressure and relying on the computer to compensate with injector on time, it can get to the point where the computer/injector combination can't react fast enough and accurate enough to control the fuel at idle. The engine uses so little fuel at idle, that it has to turn the injector on for a very short period of time, and then quickly turn it off. The electronics can handle this, but the injector is mechanical and it has it's limits.

That's why some people get into idle problems when they install larger injectors. A larger injector has to be turned on and off quicker to get a clean idle, and sometimes the limits are reached.

 

[PetroleumJunkie412]

How did the FPR fail then?
Was fuel leaking into the vacuum hose?

Yessir. Disconnected vac line and capped and clamped both ends.

 

[PetroleumJunkie412]

The problem with running very high fuel pressure and relying on the computer to compensate with injector on time, it can get to the point where the computer/injector combination can't react fast enough and accurate enough to control the fuel at idle. The engine uses so little fuel at idle, that it has to turn the injector on for a very short period of time, and then quickly turn it off. The electronics can handle this, but the injector is mechanical and it has it's limits.

That's why some people get into idle problems when they install larger injectors. A larger injector has to be turned on and off quicker to get a clean idle, and sometimes the limits are reached.

Current injectors are Saleen 24lb four hole

 

[1986RangerXL]

How would an engine behave if there was no O2 sensor?

 

[RonD]

Computer would stay in Open Loop and use pre-set air/fuel mix tables, like it does when warming up, MPG would drop down about 15%, maybe 20%

Mix tables are rich because lean melts pistons

Closed loop literally means the computer has feedback via the O2 sensor(s) so mix-burn-result-mix-burn-result-mix-burn-result is a CLOSED LOOP

Open loop means no feedback, no result, so computer just runs pre-set AFR tables

 

[wildbill23c]

Computer would stay in Open Loop and use pre-set air/fuel mix tables, like it does when warming up, MPG would drop down about 15%, maybe 20%

Mix tables are rich because lean melts pistons

Closed loop literally means the the computer has feedback via the O2 sensor(s) so mix-burn-result-mix-burn-result-mix-burn-result is a CLOSED LOOP

Open loop means no feedback, no result, so computer just runs pre-set AFR tables

These ECU's don't have the ability to tell us which injector(s) aren't firing properly correct? I was going to replace them all anyhow since the whole fuel rail has to come apart anyways, no point in replacing just 1 or 2. The ECU in the Ranger & Bronco 2 were far too old to give much detailed information like that? Any potential issues to look for when replacing the O2 sensor? Any issues replacing fuel injectors? I can't think of any but thought I would check with the experts. Thanks.

 

[RonD]

No, and new ones(OBD2/EEC-V) don't either, but new ones do have misfire detection which can be cylinder specific, which can point to a failing injector once other reasons for a misfire are checked, i.e. spark and compression

And yours is probably Batch Fire in any case, on a V6 that means there are only 2 fuel injector ground wires for the 6 injectors, so 3 injectors open at the same time, 2 on one bank and one on the other bank, then next rotation the other 3 are opened
So closer to a carb setup where the lower intake is just kept full of air/fuel mix and each cylinder just sucks in what it needs

But it can be sequential injection, just look at one bank, 3 injectors, all will have the red 12v wire, if you only see 2 different color ground wires then its batch fire, if you see 3 different colors then its sequential

 

[Paulos]

These ECU's don't have the ability to tell us which injector(s) aren't firing properly correct? I was going to replace them all anyhow since the whole fuel rail has to come apart anyways, no point in replacing just 1 or 2. The ECU in the Ranger & Bronco 2 were far too old to give much detailed information like that? Any potential issues to look for when replacing the O2 sensor? Any issues replacing fuel injectors? I can't think of any but thought I would check with the experts. Thanks.

I'm no expert, but i have learned here at TRS that unlike OBD2 systems, OBD1 doesn't have the ability to tell you much, if anything, about the injectors.

Also, when removing the old injectors, check the micro filters inside the inlet side of the injectors for debris, etc. If there's debris there, I would consider cleaning the fuel rail (acid bath). The fuel rails are known to corrode on the inside due to ethanol and/or water in the fuel; especially after the truck has sat for a length of time.

 

[wildbill23c]

I'm no expert, but i have learned here at TRS that unlike OBD2 systems, OBD1 doesn't have the ability to tell you much, if anything, about the injectors.

Also, when removing the old injectors, check the micro filters inside the inlet side of the injectors for debris, etc. If there's debris there, I would consider cleaning the fuel rail (acid bath). The fuel rails are known to corrode on the inside due to ethanol and/or water in the fuel; especially after the truck has sat for a length of time.

Thank you for the tips. I kind of figured the OBD1 don't have much to say LOL.

I'll definitely clean the fuel rail as well, I wouldn't have thought to do so, so thank you.

 

[franklin2]

Years ago I had a SVO mustang and thought I had injector problems. I took them out and took them to the Ford dealer. They had a machine there that they hooked each injector to, and was able to run some cleaner through them and check the flow and the spray pattern. I don't know if they still do that or not, but it was not that expensive and did not take them very long to do it. They let me go back and watch when the tech did it.