Alright 2001 3.0 5 speed. Let it sit overnight or during work. Turn key to run, pause a sec or two in run to let it prime then crank. Fires up in about 1-2 sec of cranking. Idle goes up to 1200 or so running smooth then settles down about 1000-900 and starts to stumble and hesitate. Best way to describe it is on an old carb car you start it full choke fires up revs high then if your not quick with the manual choke it starts coughing and stumbling till you open the choke about 1/2 way then clears up. Giving it gas doesn't seem to affect it much. It does this for about 2-4 seconds then smooths out. Reving it while it stumbles after feathering the gas clears it up slowly then revs quick. Then idles smooth as it can be at 800 or so. Press gas revs right up no hesitation. Driving it even WOT runs smooth and accelerates as good as the 3.0 can haha.

What could it be?
has 205K miles
i have cleaned the MAF with its special cleaner
new IAC
new PCV
new cam synch
new air filter

have ran a few gumout FI cleaners and seemed to have helped but that was a tank or two ago. Did have a new fuel pump put in about 1-2 years ago.
dunno what it could be...

 

With fuel injection you have a true "air pedal", no gas pedal, at least on a carb the accelerator pump would add extra fuel when you pressed down on "gas" pedal.

When you press down on the "air pedal" you are adding more air and thats it, the TPS(throttle position sensor) lets computer know more air is coming in faster than MAF will so that prevents hesitation when accelerating.

The stumble on cold start could be low fuel pressure.
Try cycling the key on and off 3 times, then start engine, see if stumble goes away.
1998 and up Rangers use Returnless fuel system that runs at 50-60psi
If you are losing pressure as vehicle sits then the 2 second fuel pump run time with key on may not get pressure high enough so engine starts and pressure drops to low so it stumbles until pressure builds up again.

Could be ECT sensor
ECT(engine coolant temp) sensor tells computer how much "choke" to apply.
All engines need to be choked on cold start, fuel injection has no Jets so a choke plate won't work.
Computer reads ECT sensor with key on, if its under 140degF or so it will apply choke, which is richer fuel mix, advance spark timing and higher idle RPMs.
The higher RPMs at startup is normal warm or cold, IAC Valve is opened all the way with Key On, when RPMs are above 400 computer closes IAC to set target Idle, 900-1,000rpm is about right for ECT reading 50-90degF, colder temps will be higher idle, up to 1,100-1,200

ECT sensor gets 5volts from computer, return wire has 3volts cold and under 1volt when engine is warmed up, so voltage drops as coolant warms up.
If..........ECT sensor's connection is lose or sensor has a problem then it could read OK for startup then with engine vibration or ??, return voltage jumps or drops, causing the stumble as computer chokes engine more or less than it should.
ETC sensors are not too expensive, or hard to replace which is why I usually say "replace it" vs testing it.
But check connector first, unplug it and plug it back in, a little corrosion on terminals can lower voltage

 

Cool thanks!

Yea once its been started for the journey like lets say leave work (sitting for 8 hours at this point) stumbles a bit then clears up. Drives fine to a store a mile away then shut it off go inside for 20 -30 min come out and no pausing with the key it fires right up and idles smooth. Drive home or grocery store same thing. Temp gauge on dash reads smack in the middle when hot and below C when cold.

Is the ranger like GM stuff where theres 2 coolant temp sensors - one for gauge one for engine PCM?

Where is this ECT on a 2001 3.0 flex fuel?

Ill check the wires and terminals and hopefully find our fuel PSI gauge.

 

Yes, pre-2004, will have a temp sensor and temp sender
2004 got digital dash so computer sent temp to dash gauge, only one temp sensor then

2001 sender will have Red/White stripe wire(to dash), and Black white stripe wire(ground)

Both will be on top front of engine by thermostat housing(upper rad hose connection)
The sensor is next to thermostat housing
Sender will be farther forward on the hexagon shaped pipe on the front of lower intake
Be careful removing it that pipe gets rusty and is a pain to change out.

Picture here: https://i.ytimg.com/vi/L_eJnt2o2-Q/maxresdefault.jpg

Wires are F*ed up in the picture
Orange top is sender


When you order the ECT SENDER you will be given a SENSOR the first time, 100% of the time, lol
So stress the word S-E-N-D-E-R
Open the box and look at the tip
sensor has cone shaped tip
Sender has cylinder shaped tip

Image here: https://encrypted-tbn0.gstatic.com/i..._ChBQ8V3BFHVSQ
CHT(cylinder head temp) is a kind of sender, just a longer version, picture is to show the tip differences

Temp Sensors and Senders are not interchangeable

 

Good to know.

This morning ready to leave for work i turned key to run and back off 4 times, heard the fuel pump whine for 2 sec each time. Started it up in 1-2 sec and still stumbles the same amount so I'm moving on to the sender.

 

Yes, good plan, just to take it off the table as the problem

Not a low fuel pressure issue from key on/off test

 

Changed sender - maybe helped? Still stumbles but maybe not as bad... Wring looked OK to it. that harness the wire goes to i unplugged and replugged all the connectors. The black rectangle about the size of a business card, 3 flat pin plug and 2 vac lines going to it the pins looked ever so slightly corroded. What is that?

 

Its the DPFE sensor. They can definitely cause a hesitation. It basically controls the EGR valve.

 

Yes, +1 ^^

Not vacuum lines, they run to the EGR tube, they have exhaust inside
DPFE sensor tells the computer how much exhaust gas is flowing into the intake when it opens the EGR valve.
One hose is closer to the EGR Valve than the other, the pressure difference between the two hose tells computer the flow rate
DPFE = Differential Pressure FEedback

I would expect a code if this was the cause and would have expected unhooking the EGR Valve's vacuum hose to settle that as possible problem or not the problem

 

Hmm good point - so if I unplug the egr valve and put a golf tee or something in the vac line to the engine and drive it, it will throw the SES light I know but would this eliminate the DPFE as a potential problem? I know it will eliminate the egr as a potential problem as well thats supposed to only open under a load and at speed not idle but if its sticky or leaks it can cause all sorts of issues as well.

I do have a code reader and no check engine lights or stored codes for anything when i check. Like i said once its warmed up runs and idles great. Maybe when the AC is on it it makes the truck vibrate a bit more but doesnt feel or anything like the morning startup with the AC off...Ill see if i can grab a video of its startup so you guys can hear it.

Is there anyway to test this DPFE sensor alone? or another way to word it is once i plug the egr and the problem is cured how do i know if its the egr or the sensor?

Only other things on my list of things to change are the O2 sensors - factory ones from 2001 with 205K miles on it but from my understanding the O2 sensors dont come into engine management play until it goes closed loop (aka warmed up). is that correct thinking?

 

O2 sensors need to be above 600degF to work, so yes the computer ignores them until they start switching voltage very fast, there is no timer, computer watches ECT(coolant temp) and O2s voltage switching to decide when it should try Closed Loop.

O2 sensors are also ignored at idle and at WOT(wide open throttle)
Idle needs Rich mix or engine will overheat
WOT is all about power not fuel economy, O2s are ignored


If EGR valve was leaking you would have a rough idle, so we can assume it is not leaking.
If you disconnect its vacuum hose, and plug it, then EGR valve can not open.
If EGR system was causing the drop out, it would go away if EGR Valve couldn't open.
You might get pinging/knocking on hard acceleration but no drop out.

As said exhaust gases slow the burn rate of rich fuel mix so reduce cylinder temps, no exhaust gas means cylinder temps can spike high, and this can cause pre-detonation, i.e. pinging and knocking, on regular 87 octane gasoline

 

Ive plugged the egr for S&G. seems like its got more oomph and drives smoother. Drove 14 miles with it plugged and no engine light yet. Will run it for a tank of gas and see what it does and watch the AM startups.

Last tank i got 20.3 mpg.

 

Started it cold this AM with plugged EGR - hardly any stumbling. I have noticed even before i plugged it if i start the truck with the AC on it doesnt stumble nearly as bad. I know the AC being on jumps the idle up 100 or so rpm right? Could something be not "choking" it enough?

engine light did come on finally so no surprise there.

Going to try a few times with AC off EGR plugged and see what that results.

Every vehicle ive plugged the egr or completely removed it seems to run so much better at low speeds- granted they were all high mileage when i did this...

 

Reads like leaking EGR valve

EGR system will give better performance on Regular gas because spark curve can be less advanced, don't have to head off pre-ignition

You want full explosive force in a cylinder when the piston is about 10deg ATDC, earlier and you don't get best leverage pushing down on crank, later and you aren't adding as much power as possible.
Standard 14.7:1 air:fuel ratio has a known burn rate from spark to full explosive power, and thats what base spark timing is, 10deg BTDC spark has full explosive power at 10deg ATDC, but thats at 650rpm for example
When RPM increases the piston is moving faster from 10deg BTDC to 10deg ATDC, but the burn rate stays the same...........so spark has to be advanced to say 20deg BTDC to get full explosive power at 10degATDC

And thats what centrifugal spark advance did in distributors, the weights

If you have a Richer fuel mix, i.e. accelerating, that changes the burn rate, it burns faster, and thats what Vacuum spark advance was for, it retard the spark for the faster burning rich mix.

Computer does all this calculating of spark advance now
With EGR system the spark curve needs to be less aggressive to avoid possible pining/knocking
With EGR system computer can adjust spark for best power.


If a computer controlled engine runs better without the stock EGR system, then something was wrong with the EGR system, lol.

 

hmm my options are leave it plugged (free) or $43 for a bwd one...Like i said im gonna leave it plugged and see how it does. Started just fine after work with AC off no stumbling stayed higher idle longer but eventually settled down to what it thinks is normal. I know its probably not good for the catalytic converter to leave it plugged tho...

 

If removing the vacuum hose from the EGR Valve helped then EGR valve is probably OK.
The problem will be the EGR solenoid most likely.

The computer controls the EGR solenoid, it is a vacuum valve that passes vacuum to the EGR valve to open it, a little or alot.

EGR solenoid gets 12v key on and computer controls its ground.

If the EGR Valve itself was leaking then disconnecting vacuum hose wouldn't change anything, it would still be leaking.

But if the EGR Solenoid valve was leaking vacuum..............then it would pull open EGR valve slightly causing issues with idling or in some cases running.
EGR solenoid has full vacuum access all the time, it should be hooked to the Vacuum Reservoir, like the cab vent system, so it can hold EGR valve open when intake vacuum drops, i.e. when accelerating, which is when EGR system is used the most.

EGR solenoid should not pass air from port to port when power is off, and should pass air when powered on, 9v battery or car battery.

Pretty easy to test it
And then test its two wires, key on
One will be 12v the other not a ground, lol, i.e. if you connect volt meter to the 2 wires it should show 0 volts, key on engine off
Then start engine and it should also should 0 volts, might go up and then drop back down, depends on if computer runs an EGR test.
Slight steady voltage on the 2 wires would cause vacuum to pass and hold EGR valve open a bit

 

sounds easy enough to test. Ill mess with it tomorrow and see what it shows.

appreciate your help Ron! Usually on my vehicles when the cat dies egr aint far behind so generally both get removed from my vehicles so ive never really troubleshooted the egr system (that and the egr valve has been stupidly expensive - single port vacuum one for my s10 was $94 for the aftermarket replacement - delco one was well over 100 bucks...no electronics at all just a single vacuum line...)

 

Alright tested some of it, key off 0v on both wires. Key on 12V to one wire 0 on other.

Now i took a piece of vacuum line and stuck it on the upper port - sucking air just sucked straight thru and the thing buzzed. blew air thru it and it blew air out the bottom port. Plugging bottom port while blowing i couldn't force air thru. Hose on bottom port, sucking caused it to buzz but blowing i could slowly pass air thru the upper port but took a bit of effort. This was all key off or electrical conenctor unplugged so you say it should not pass air either direction thru the ports?

Sounds like its leaking to me...

Started raining like a **** to try engine running voltages...

 

Yes, it should not pass air in either direction when close, if it does then engine vacuum will pass thru and pull EGR Valve open a bit when it should be closed

If you go to a parts store take a short hose with you and test a new one, should be tightly closed

 

Hmm bought a new BWD one and upper port when blowing air passes thru to bottom port the same as my old one and bottom port when blowing air slowly passes thru to top same as old one...This is unpowered mind you. does it need to be powered to do its thing?

 

No, doesn't need power

Any vacuum solenoids I ever test were firmly closed with no power, may the EGR valve has a strong enough spring to prevent opening unless vacuum gets above 3" or so???