If that's the case why would the scanner show that when the problem is happening that it's cutting back the fuel? Like its purposely choosing to give the engine less gas

 

I have noticed that it is worse when it's been raining or is very humid outside.

 

how old are your spark plug wires

 

They were replaced before I bought the truck about 1.5 years ago but they all look good. I pulled them out and inspected each wire and also checked the resistance through them all. If they were bad I don't know how that would only make problems when the motor was loaded. Any ideas?

 

I tried to find PID ranges for the Sct sf3 and no luck.

PID is Packet ID, each sensor and control has an unique ID tag, a number, when you select the TPS, or STFT the reader uses that PID to access that data from the computer(PCM).

The programmer(guy who writes the interface software for your SF3 model) for SCT will assign a range for each PID.
Most reader's software will use a % for the TPS or a voltage, 0% to 100% or 0v to 5v
So when the PCM sends its "position number" for the TPS to the reader, it will be in computerese, binary numbering, the reader's software translates that to "english", like 20% or .89volt, for closed throttle, which is good, understandable without much learning, lol

SF3 is using 7.6 for closed throttle from what I have seen, but not much use unless you know the lower and upper limits for this PID and software.

Same for STFT, in my mind .89 would be less fuel flowing than 1.00, but really don't know.
There should be a manual online for the SF3, and it should have the ranges and how to read them

Yes it is a tuner/datalogger

 

depends on the brand of spark plug wire

napa / orieilys / other are really crappy wires

over time the wires insulation breaks down

a easy way check for leaking spark plug wires is wait till night fall

prop the hood open , start the engine and with a water spray bottle , spray around the spark plug wires

and look for a BLUE electrical light show , ( almost like continuous lightning strikes over the engine )

 

Ron I'll see if I can find more information on that thanks a lot!

And I've done that in a closed garage with the truck running in darkness and a spray bottle set to mist and never saw anything. I also removed them and inspected the insulation and tested the resistance with their length in mind. I couldn't find anything wrong with them and I'm not sure why t would only be while under load that they would have problems.

 

i was reading another article about the same problem

it turns out that the pistons had sooo much carbon buildup on them that were absorbing the fuel preventing the fuel from igniting when the spark plug fires

i would borrow a inspection video camera and check the combustion chamber(s) for excessive carbon buildup

and run several tankfuls of 91 octane fuel with 1 can of seafoam to clean out carbon buildup

 

Thanks for letting me know man! I'll take a spark plug out and check for that. I've never heard of that but it's worth looking into. Since I've had the 91 octane in there and been driving it with that in it, it has been running better today but not completely ok. I've done sea foam in it before but may have to do it again

 

91 octane is all i use now

tried a couple tankfuls of 87 octane fuel , the ECM did not like it at all , no pinging but mileage went south .

you should also switch to nickel spark plugs , instead of platinum , even the mazda mechanic switches mazda engines over to nickel plugs , he states the engines run alot better with them

 

I used the seafoam in the brake booster line and then filled up with 91 octane again. 91 is the highest I could get without drive far to get 93. Truck is still acting up. Where is the inexpensive Bluetooth obd2 readers? Anyone have any recommendation on a cheap one that will tell a good bit of live data

 

how many miles have you driven so far on 91 octane fuel

just a suspicion ,,, but how long since you replaced the oxygen sensors on your ranger

 

Maybe 100-200 miles on the 91 octane fuel. The rear o2 sensor I replaced once I found there was a code for the heater circuit in it. That was probably a year ago. The other two sensors before the cat I've never replaced since I've owned it

 

Ron you know of a scanner that's good? Blue tooth kind you were talking about.

 

just found out from the mazda mechanic

any time you replace oxygen sensors , the ECM must be deeply reset

meaning the ECM software ( operating system ) must be rebooted

to start reading from the new oxygen sensors , or the ECM will continue to read from a pre-programmed fuel trim

 

How do I reset?

 

to do deep reset

the ford mechanic will have to do it , as i am told , it requires special software only the dealer has access too

 

I'm pretty new here and still learning, but the last time I checked one has to shut off all accessories, disconnect the ground on the battery.

Make sure it doesn't accidently touch the ground (I use a rag)
Connect the negative and positive terminal together to drain the capacitors.

I left mine sit for 20 minutes.

With all accessories still off connect the ground _ make sure your doors are closed when you do this.
You don't want arcing when connecting the ground.

This procedure will also clear the check engine light too. (at least it did on my truck)

 

the ECM uses a small lithium battery to maintain ( keep memory alive function )

dis-connecting the main battery does NOT reset the ECM`s operating system

the mazda mechanic made it clear to me , that dis-connecting the main battery does nothing

their computer is on a cart that uses sophisticated software that does the vehicle ECM software reboot

 

I took the cover off my ECM (PCM) to inspect it and I don't remember seeing any battery in there.
I was looking for burned circuits and/or corrosion.

I'm not trying to argue with you, but just trying to understand things.

If the battery is not inside the PCM, where else would it be ?

Ron mentioned in another thread that the computer will learn when a new component is installed based on the hard memory of the chip set by the factory.
Why would one need to change that memory ?

Why would an oxygen sensor need any special attention compared to any sensor for that matter eg. the cam shaft positioning sensor.
Some doofus installed my synchronizer more the 90 degrees out and the computer recognized the correct position right away after a fixed it.

 

I know a guy with a 2000 dollar computer. Think that would do it?

 

the ECM motherboard is exactly like a computer motherboard

it is small flat circular battery that maintains learned presets and connected sensors

even if the main battery is dis-connected , the keep memory alive battery is powering the ECM motherboard , and will detect any sensor that is dis-connected including oxygen sensors

if the computer detects a failed oxygen sensor , then the ECM software will switch over to the pre=programmed fuel trim program

as told to me by the mechanic , only a deep reset will force the computer to start reading from the new oxygen sensors instead of the fuel trim it was reading from

 

You have to have a PCM(computer) programmer to clear the Long Term Fuel Trims(LTFT).

Thats what needs to be reset but....................it should only take 3 to 6 days for LTFT to correctly reflect new O2 sensors.

LTFT is saved in memory because it is used to run engine when it is cold, when there are no O2 sensors to use.
So you DO NOT want to erase it when you reset computer, or reboot it.
Thats why you need correct software to clear LTFT.

But it does self correct from driving the vehicle, so really not a big deal

 

That makes sense.
I put a badly needed oxygen sensor in my old B2200 (it was getting horrible fuel economy)
Shortly there after the fuel economy came back, but I didn't have to go to the Mazda dealer and have them reset anything.

 

the newer models have more sophisticated ECM software now then back then in 1999