Brand new to this forum. Shade tree mech at best. Looking for advice.

2001 Ranger 3.0. 130,000 give or take.

Check engine code revealed issue cyl 4.

Plugs, wires, coil r and r. still flashed after a short drive.

Compression o.k.

replaced fuel injector cl 4. Light stayed off over a week.

Has came on again, but no flashing.

Am I right to assume it is a fuel issue?

 

Welcome to the forum


The PCM(computer) knows an engine will misfire all the time, all engines do, just FYI.
The PCM keeps track of misfires, i.e. RPM, engine temp, throttle position, cylinder #
If there is a reoccurring misfire then PCM will notify driver with CEL on, flashing CEL means engine damage could occur, and it will usually stop flashing once load is taken off the engine.

Compression is OK, what does OK mean?

3.0l runs 9.3:1 ratio, so 165psi would be expected
And compression test has to be done on 3 cylinder at least to determine OK, reason being compression gauge and crank speed are not consistent, so a sample is needed for comparison.
Best test is all spark plugs removed
Then test each cylinder.


No, in changing the fuel injector #4 you have to move around the wiring and coil pack, so you could have simply fixed a wiring issue temporarily by that action.
But good news is that it probably took compression issue off the table, outside of the exhaust valve seat issues on the 2003-2006 3.0ls compression doesn't tend to be intermittent, it is a hardware issue, so problem wouldn't go away and then come back


Fuel injector is just a solenoid/valve connected to a common fuel rail.
If you changed the injector on #4 and it stopped the misfire then you would assume bad #4 injector was the problem and all is well now with new injector.
But the fact that the #4 misfire returned would mean the injector was not the problem.
Fuel injectors just do not fail very often to begin with, people often change them on spec, they do get dirty, use Seafoam in gas tank to clean them.

Since fuel injectors share common fuel rail it would be hard to say this is a fuel issue since other injectors are not also effected.
Each injector does have it's own wire back to the computer, so computer can open each injector at the correct time, if the connector at the injector or at the computer was corroded then that could effect just that one injector.

The 2001 Ranger has the Computer connector in the upper center of firewall, these did get a cover added in 2003 because of water getting into the connector, leaking hood gasket allowed water to flow onto the connector.
Since you had to unplug the #4 injector and plug new one in it could be that connector is corroded or loose, so it lasted a week then started cutting out again, give it a close look, much more likely than computer connector.

But computer connector could also effect Coil Pack as well so worth a look

 

Well, my bluetooth code reader came from Amazon. The code is now P0401.
This is such a relief that it isnt missing!

If you dont have one of these $10 readers, I highly suggest one. So nice.

I think I probably need a new gasket on the egr, since I didnt replace it when I r and r the fuel injector.

 

P0401 is almost always the DPFE sensor, common issue on Fords.

But check the DPFE sensor hoses they get water inside and plugged up, they look like vacuum hoses but connect to exhaust, EGR pipe.
It does matter which hose is on which port, so keep track of that

 

is the the little doohickey on the front of the upper intake with 2 hoses?

 

I just had the identical issue with my 2003 Ranger 3.0L Flex, I started with changing out the plug and while that helped, I changed the coil pack and we are back to a nice smooth idle and no MIL...

 

Well, my issue was solved for nearly three weeks. Light is back on, flashing with misfires on 3 and 4. ??? I put a new fuel filter on as well.

WTF?

any suggstions?

 

I've noticed that 3 and 4 are on the same tower. I have tried a different coil,albeit is not new, but the result is the same.

 

Yes, 3 and 4 share the same coil, as do 1/5 and 2/6

Check the 4 wire connector on the coil pack
1 wire is 12volts with key on
Other 3 wires are the Grounds for each of the 3 coils inside the coil pack

So 3/4 coil will have its own wire back to the computer, computer Grounds the coil to power it up then cuts the Ground to spark the coil, same as all other ignition coils.

It could just be a loose connector or could be computer issue, computer has 3 separate transistor setups, one for each coil, to ground and unground each coil

2001 Ranger did have computer plugin in upper center of firewall, and there were issues with water intrusion in this setup, later models got a water resistant cover plate.
So may be worth while to unhook battery and pull off that connector to have a look for corrosion.

 

RF Veteran.
Thanks. I will pull and look for corrosion. I am comfortable feeling I am on the right track. Since 3 and 4 are missing together now.

Will update.

 

Ford's Waste Spark system wires 2 spark plugs in series, like 3 and 4
So one spark plug will spark from center to tip(normal) the other one will spark from tip to center(reverse)

This is why you should only use regular copper spark plugs or Double Platinum, single platinum will be the same as regular copper on one bank, so waste of money.

This also means one bad wire or spark plug could effect 2 cylinders, series wiring requires complete path to ground

 

Ron D.

Well, it was that damn plug on the firewall! I didn't notice ant corrosion, but r and r and the truck doesn't miss. Drove 75 miles this morning...smoooooth. No light.

Thank you!

 

Good work

Thanks for the update and what fixed it

 

Hey guys.
Not wanting to kick over a can of worms, but a garage locally talked me into going straight pipes from the manifolds back. I'm dealing with about 12 MPG, but I was before the exhaust mods as well.

I of course am getting codes. P0171 (due to the rear 02?) and I also get a P0401 on the EGR Flow.

Bank 1 too lean...whats that all about?


Anyway to get this mpg back to par?

138,000 miles.
New plugs, wires, fuel filter, egr as well.

Please don't preach about emissions and cats, I know, I know....

 

All Rangers have a stock Tuned Exhaust, tuned for mid-RPM band power
Just FYI

P0401 - EGR flow is most likely a DPFE sensor problem

EGR system has 4 parts
The Computer
The EGR Valve
The EGR solenoid
The DPFE sensor

NOX is a toxic gas
NOX levels spike very high when cylinder temps get high
Cylinder temps get high when engine is under load

If you add exhaust gases to the cylinders it lowers the cylinder temps, yes HOT exhaust gas LOWERS temperature in cylinders, lol, go figure
Doesn't hurt power, just lowers temp, as a positive side effect........EGR system prevents Pinging/Knocking, which are caused by higher cylinder temps pre-igniting fuel

So the computer will open EGR valve using the EGR solenoid when engine is under load to cool cylinders
EGR solenoid is hooked to engine vacuum and EGR valve's vacuum valve
Computer can vary voltage to EGR solenoid to open it a little or alot, to sends a little or alot of vacuum to EGR valve, adding a little or alot of exhaust gases to the intake/cylinders.

DPFE(pressure feedback) sensor is hooked to exhaust manifolds EGR tube, in TWO places
It measures the pressure difference between the TWO hoses
One hose is near the EGR valve, the other farther away
As EGR valve opens the pressure will drop in the closest hose but not as much in the farther away hose, this pressure differential tells Computer how much exhaust gas is flowing back into the engine.
Computer can then vary the flow based on RPM and load.

P0401 means either DPFE sensor or its TWO hoses are having a problem OR.....EGR valve or its exhaust manifold tube are having a problem, getting clogged up

Computer is trying to get correct flow but can't
And it could also be the EGR solenoid, a vacuum leak so computer can't fully open EGR valve.

Leaking or stuck open EGR valve will cause lower MPG and general lack of power


P0171 - bank 1(passenger side), O2 sensor 1 was Lean, computer setting for fuel injector open time is higher than it should be.
Computer calculates fuel injector open time based on RPMs, throttle position and MAF air flow data.
After fuel is burned on Bank 1 that O2 sensor is showing too much Oxygen in the exhaust, Lean burn, not enough oxygen is Rich burn, O2s can only see Oxygen
So computer will open injectors a little longer on Bank 1 to get lower oxygen level
And it will open them longer and longer until O2 sensor reports Oxygen Level is correct
Computer has a limit marker to set a Lean code if its calculations are too far off, to give the Driver a "heads up" that something is wrong
Engine was/is never running Lean.

Exhaust manifold leaks SUCK IN air, so will give False Leans and cause low MPG.
Failing O2 sensor causes false Leans.

The Rear O2 sensor is called the Bank 1 Sensor 2, and it has its own Codes, P013X
So no, P0171 is not related to that
Since you are not using rear O2 swap it with Bank 1 sensor 1
Rear O2 sensors see "cleaner" exhaust so last much longer than front O2s
But you should have some P013X codes if rear O2 is not connected or installed

 

@RonD this is the exact same issue my truck has, but the OP on this thread is apparently way better at describing things than I was in my post. However, the conditions at which these issues occur remains the same. Below 4000 rpm everything is good but at WOT above 4k is when my engine unloads and evetything goes to hell.