2001 XL 2.3l DOHC RWD

I have been hunting down the problem causing a stutter in acceleration when the throttle is open 30 degrees or more. I have a question about Spark plugs and fuel dilivery. Im getting a p0171. I have cleaned/replaced/checked:

MAF - cleaned
TPS - replaced
MAP- Cleaned
IAC - Cleaned
Air Filter - Cleaned
Fuel Filter - replaced
PCV - replaced
Confirmed no vacuum leaks using the IAC test suggested by @RonD
NGK Coil - replaced
Wires - replaced

All of these I confirmed were in spec using an OBDMate, multimeter, or diagnostic gauge.

1. When gauging fuel pressure using schrader valve, at key on/engine off was 35psi and 60psi at idle. After shut off fuel pressure seemed to ebb slowly as expected. I also confirmed that my injectors were not leaking. My question is when at 60psi during idle i would open the throttle, the pressure would drop secondarily to 50-55psi then shoot back to 60. is this normal?

2. Spark plugs :(
everything I see online states that spark plug resistance should be 3000-5000 ohms. I just bought a new set of motorcraft plugs(Ford Recommended) and installed them, then pulled an tested them, 2 of them were 9.3k ohms and one was 10k ohms and cylinder 3 was at 14.4k ohms. I just picked up a new box of plugs, the exact same type. All of these tested between 5.2k -6k ohms. I have a couple of NGK testing at 4.3k. So........ What is the correct resistance range for me? Can I use any plug I have? Was there something I could have done to the plugs that are now testing 9 and above? A new spark plug should have less resistance than a used one of the same type?

Thanks in advance

 

In 2001 the FPR(fuel pressure regulator) is in the gas tank with the fuel pump, so yes there could/would be a slight delay in responding to fuel demand at the engine end with a pressure tester
But would need to drop more than 20psi to effect engine performance, 5-10psi drop and return is expected

2001-2003 2.3l Rangers used IMRC(intake manifold runner control) this setup was known to cause running issues, Ford dropped it in 2004 2.3ls

Google: Ford Ranger IMRC symptoms

P0171 System too Lean (Bank 1)
This is a fuel calculation code, doesn't mean engine is actually running Lean, an engine will ping/knock if its running Lean

The computer calculates open time for each injector, based on air weight and pressure(MAF and MAP), air temp, engine displacement, RPMs and throttle position(load)
It ASSUMES, fuel pressure at 55psi, and injectors are stock size
That amount of fuel is added
O2 sensors can ONLY see Oxygen
Computer then looks at O2 sensor feedback to see if there is too much oxygen in exhaust(lean) or not enough oxygen in exhaust (rich)
Computer then adjusts open time for the injectors to get oxygen level at the correct point
This all takes less than 2 seconds, if that

IMRC directly effects combustion in cylinders, so effects oxygen levels seen by O2 sensor

If computer is constantly having to lower the oxygen level in exhaust it will set a code like P0171, letting the driver know there is a consistent issue causing its calculations to be off
Vacuum leaks and sensor errors can of course cause this
Low fuel pressure as well for P0171
AND
Exhaust blockage, this usually ONLY shows up at higher RPM and limits top speed/RPMs

 

@RonD

thanks for the info.

I think I’m reading that my fuel delivery is working. Also I should investigate the IMRC.

Do you have any info about my spark plug situation. Mainly I want to know if I can return the ones I bought today in the 5k-6k range and use the 9k ones I have. Should all four be similar resistance?

 

Yes, it will use resistor type spark plugs to reduce radio noise, AKA, suppressor type spark plugs
Lawn mower, snowblowers and outboard boat motors often don't use resistor type because.......................no radios, lol, well usually

The ohms difference you are showing wouldn't matter much
Spark plug wires average 10,000-14,000 ohms per FOOT
So even a 5,000 ohm difference would be like having a 6" longer spark plug wire, which wouldn't matter in the least

Gap matters more and Heat Range, 0.042 to 0.044 is the gap when I looked it up

 

Thanks @RonD

I understand what you are saying about the wires but what about the plugs themselves. That’s what I’ve measured all these resistances. I know it’s confusing. When I try and type only “spark plugs” info, all the search engine hits are for spark plug wires. It’s so dang hard to get info on just plugs.

I guess, what is the operating range for just a plug in ohms for 2.3l Rangers? Do all plugs need to be relatively in the same range?

 

Just as a heads up, when looking for engine parts, use 2002 Ranger 2.3l instead of 2001
Rangers had the 4cyl 2.5l Lima engine in 2001 and then in June of 2001 they got the 2.3l Duratec engine so mid-year engine change
This can get very confusing for on-line sites AND even local parts stores, lol
2002 ranger 2.3l was exactly the same so use it in searches

No, matching high ohms wouldn't matter, same as spark plug wire lengths can be different, within reason, V8 engines have 10" spark plug wires up thru 30" spark plug wires, thats a 20,000 ohm difference, minimum, from 10" wire to 30" wire, but spark plugs all fire at the right time and fully ignite the cylinders they are in

Ford specs the SP-439, officially AGSF32FEC, for the 2.3l Duratec engine, model L Mazda engine

Motorcraft spark plug number decoder seen here: MotorCraft Spark Plug Information - Jim's Site

AGSF32FEC is the number to decode, but won't give you ohms, just that its a "suppressor"(resistor) type spark plug

As far as the exact ohms on each spark plug I would expect to see new unused spark plug of same model, to be similar ohms, so your 5,000-6,000 looks OK
Used spark plugs will usually be higher after a month or two of use, so yes, used spark plugs will usually test at higher ohms, as they do run very hot

But as said 10,000-15,000 ohm used spark plug works just fine, like it had an extra 1ft of spark plug wire on it

 

@RonD thanks so much.

is there a way to bench test or test the IMRC valve/system? It’s 130.00 for the part and I’d like to try an spare myself.

also, after remounting the Intake manifold I got the runner control clicking. I noticed I had knocked it off it’s spring loaded arm connected to the actuator. I put the ball back in it’s joint but I’m still getting the clicking or it’s even worse. Do the butterfly flaps need to be oriented a certain way? Am I missing something?

 

Sorry don't have one to test

Google: Ford Ranger IMRC

Seems to be alot of info out there on how they should work and symptoms of when they are not working


Just as a "what it is for"
Intake manifold "runners" are the air passages that run from the Carb or in this case upper intake, to the back of the intake valves
When an engine is running and intake valves are opening and closing, each time the intake valve closes, air flow is suddenly STOPPED, this creates a Pressure Wave that goes backwards up the "runner"
When the Pressure Wave hits the upper intake(or carb) it reflects back toward the intake valve
If that Pressure Wave hits the back of intake valve just as it opens again its like a mini-turbo BOOST, it pushes more air in, so you(computer) can add more fuel and get more power

So there is an "art/science" in intake manifold design as far as the "runner" lengths and at what RPM the intake valves need to be at to get the "mini-boost"

IMRC has flaps that in essence change the length of the "runners", so it will have two different RPMs to get that mini-boost
On paper its a good idea....................and does work, until it doesn't and there is a problem with it, lol

Ford dropped it in 2004 2.3ls because of issues

 

@RonD

i can’t find any info but does 820 ohms for the IMRC actuator sound right? Is it supposed to change in resistance as the spring is pushed in? I hope actuator is right. It’s the “swirler “ with the spring arm on the back of the IM.

A diagnostic video for the IMRC actuator stated the resistance for the solenoid is about 30 ohms but I can get info for the actuator..

my IMRC solenoid valve has passed all its tests so far.

thanks.

 

Sorry I don't have a way to test IMRC components, so don't know what they should read

 

@RonD

I just tried going for a spin without the IMRC and the tubes winched off. There was no change, worse even, but not because of that. It was a colder day than when last I drove it.

im thinking I missed something for p0171 code this is all causing.

my MAP says 29.2 inHg at about 55 degrees. Sound right? I tried replacing it once with no effect

my O2 readings are:

before cats- o2 sensor bounces between .1 and.7ish. I think that’s normal

after cats - o2 sensor doesn’t always stay on .7ish. It bounces around at idle but my understanding is the computer is ignoring it then but when I’m accelerating or driving it will jump down to .19ish. It’s a brand new sensor too.

An exhaust blockage could be causing this? The cats are brand new but the muffler and pipe past the cat are old As the truck I bet.

is there like a total computer reset? Can the PCM be adjusted?

 

No, PCM can't be adjusted unless you have the software to do that, its expensive

Look at local airport websites, smaller airports will have local barometric pressure and temp on their site for private pilots
Barometric pressure(and temp) is specific to your location

After cat O2 looks OK
Upstream O2 sounds OK

P0171 would be set by upstream O2 sensor showing too much Oxygen(lower voltage) in the exhaust manifold, when running on Computers fuel calculation
So computer opens fuel injectors longer to lower the oxygen in exhaust, if that longer open time exceeds 20% then P0171 code is set

O2 sensors use
0.1v for high oxygen
0.9v for low oxygen

0.4v is the sweet spot the computer tries to maintain

Computer's air/fuel calculation is based on engine size and fuel injector size/fuel pressure, RPMs, throttle position, and sensor data for air weight(MAF), and air temp
Engine size is probably not changed, lol
injector size either, but only you would know
fuel pressure should be 60psi, +/- 8psi, there is no fuel pressure sensor
RPMs are what they are, so are OK most likely
Throttle sensor as well, as it would set its own code if failing, throttle sensor and MAF are linked as "compares" so they are tested against each other, and codes would be set for these if either was "out of range" of the other, or RPMs

Air temp is important since air gets HEAVIER when its cold, i.e. "hot air rises", thats because warmer air is lighter, think hot air balloons
Air/fuel mix of 14.7 to 1 is a WEIGHT ratio, 14.7 pounds of air to 1 pound of gasoline

Intake air leaks means computer is doing the calculation with the wrong data, unreported air is coming in so its calculation is wrong
1st rule for computers is "garbage in = garbage out" this doesn't mean computer's never make mistakes, but 99.99% of the time it not a computer issue, its bad data

Lower fuel flow, same thing, computer is basing its calculation on wrong data

 

so, it couldn’t me my MAP sensor or an exhaust blockage?

 

@RonD

i just back probed my MAP and got these numbers

@ warm and at idle, 790rpms, 1.26v, 9.3inhg

2400rpms, 1.16v, 8.6inhg
3000rpm, 1v, 7.7inhg

The info I found online I dates the numbers should be going the other way.

Are these reading what I should find for the MAP sensor?

 

Yes, that seems to be reversed readings