I’m doing some work on my uncles 2002 4.0 v6. Had gas in oil no engine problems yet. changed injectors, plugs, plug wires, coil pack, IAC, cleaned MAF, oil pan gasket, valve cover gaskets, serpentine belt, air filter, oil change. Injector for cylinder 4 had a wire that goes into the firewall to the computer(ground??) spliced in, that wire popped out and I soldered it back in. Is that wire supposed to be there? starts up fine about 10-15 seconds after start up starts to stumble, surge, drops to 500 rpm and stays there. engine revs up fine no hiccups. First time on forums direct me elsewhere if needed thanks!

 

Welcome to the forum

Each injector has a 12volt wire(RED) it shares with the other injectors, so one wire that is daisy chained to each injector
Each injector has its own ground wire that runs back to the computer, so 6 wires on a V6, computer grounds an injector to open it in the firing order for the engine, called Sequential Fuel Injection

2002 4.0l #4 injector should have a brown/light blue striped wire that runs back to the computer

Does it idle/run better after it warms up?


You can get a $15 Bluetooth OBD2 reader(ELM327) and a $5 TorquePro APP for your phone
Works with ANY vehicle 1996 thru 2024, not a Ford thing or even a US car maker thing, ANY vehicle sold in US/Canada is required by law to use OBD2 after 1995

The reason to have this is to watch LIVE DATA from all the sensors, so you can see what the computer sees and what the computer is doing
Also reads and clears codes, lol
Sensors are expensive, so you can see if a sensor's data/voltage is out of range or incorrect, if not then doesn't need to be replaced


I think you may have an ECT(engine coolant temp) sensor issue, so engine is not being Choked on cold start
There are TWO temp units on 2002 4.0l
ECT sensor, 5volt, ONLY used by the computer, for Choke
Temp sender, 12volt, ONLY used by dash board temp gauge
They are both on top of the thermostat housing in the 4.0l SOHC engines, and NOT interchangeable

ECT usually has a grey/red wire and a green/red wire
Temp sender always a red/white wire, and if 2 wires, then a black/white wire

Make sure both are plugged in

Gasoline engines need to be choked on cold start, this means Richer fuel mix and higher idle, without this the engine will struggle to run UNTIL it warms up
With an OBD2 reader you can SEE what temp the computer sees from the ECT sensor with key on, should be outside temp
Then it should show increasing temp after start up as engine warms up

 

Thanks for the response, Both of those sensors are plugged in, I get an overwhelming fuel odor when she starts stumbling during idle. Most its idled for is 2-3 mins just feels like somethings going to give lol. When it warms up should something change indicating a part needing replacement? Thanks once again.

 

Owner of the vehicle says in the last 2 years that he’s owned the truck the transmission didn’t want to shift out of first gear 3-4 times. Says he’s pulled over turn the car off turned it back on and has worked every time. Could that ect sensor be the culprit for that as well? car shifts fine except for those few incidents.

 

No on the shifting and ECT
The 4RxxE and 5RxxE transmissions can do that when cold, but only when cold
A transmission doesn't warm up much by starting engine and letting it idle, putting trans in gear for 10-20seconds before moving warms it up faster

Prior to the work on the 2002 4.0l SOHC Ranger what were the issues?
i.e there was a reason for the "changed injectors, plugs, plug wires, coil pack, IAC, cleaned MAF.............."

Why the injectors?
poor MPG, stumbling

Plugs and wires are normal to change, as is cleaning MAF(once a year), coil pack is optional these rarely fail
IAC Valves rarely fail but are replace often, lol, you can only use Motorcraft or Hitachi brand IAC Valves, if you can't find new the used factory IAC Valve from wrecking yard is better than new 3rd party

Not sure what "Most its idled for is 2-3 mins just feels like somethings going to give lol.", means in this context?
Is there a noise or smoke or ????

Yes, computer has 2 basic modes of operation, cold engine is Open Loop(uses a few sensors), warm engine is Closed Loop(uses all sensors)


There is a test for leaking injectors, called "Clear Flooded engine mode" all engine computers have this
Key on(computer is on), engine off
Press gas pedal down to the floor all the way and hold it down
(when computer sees 0 RPMs and WOT(wide open throttle) it will shut off injectors for Clear Flooded engine mode, allows driver to dry out a flooded engine)
Try to start engine
It should NOT start or fire, has spark but no fuel from injectors, should just spin
If this happens then no leaking injectors

If engine fires/starts then possible leaking injector, but.................need to check for WOT from throttle sensor(TPS), would be good to have OBD2 reader for this, lol
Key off
Put a stick on the gas pedal to push it down all the way, other end against the seat to hold it down
Go to the engine and see if you can open up the throttle a bit more, if so then no WOT signal to computer
Google: Ford Ranger throttle cable mod
Simple fix to get WOT again
Repeat Clear Flooded engine mode test again

 

Came in for rebuilt suspension front and rear, had puddles of oil on my floor had oil all down the block pulled the stick to see if he had oil and it was halfway up the dipstick smelling like gas. That’s why Injectors were changed. Gas has been eating away at the seals and were leaking that’s why valve cover and oil pan gaskets were changed. Never had a tuneup owner had it since 120k it’s at 170k he didn’t have any service records, complained about poor mpg figured new plugs(NGK-7316)wires(NGK-52015), coil pack(standard motor products FD-480T), and injectors(FJ438) wouldn’t hurt. Started it up that’s when I started having the problems, cleaned MAF didn’t work, cleaned IAC then replaced it, cleaned both sides of the throttle valve still having problems. Yes, there is white smoke coming out the exhaust and little backfires during idle. I let it get warm today and seemed to get slightly worse as it was creeping up in temp still smoking still stumbling. have a video of the tac bouncing if I can post it here or get your Facebook or number.

 

On the fuel rail is a Pressure damper at one end, has a vacuum hose attached, check that vacuum hose for gasoline, shouldn't be any of course

Recheck coil pack wiring, easy to reverse a wire or two which causes the back fire and rough running
1 2 3
5 6 4
front

Diagram here: https://www.explorerforum.com/forums...ohc-jpg.62630/

The 1 2 3 is usually OK, the 5 6 4 side is what can get reversed, its not 4 5 6
Follow each wire from coil to cylinder, then do it again, then have a friend do it
There are 2 kinds of people that work on gas engines, people who have messed up firing orders and LIARS who say they haven't, lol


White smoke out the tail pipe indicates moisture in the exhaust system, but should go away as exhaust gets fully warmed up, but if its cold out(you can see YOUR breath) then you will see a little white smoke even after warm up

If it stays alot of white smoke then blown head gasket can cause that, but simple test for that
Cold engine
Remove rad cap
Top up radiator if its low, should be full to the top
Start engine
Watch rad cap opening
Might see an initial "burp" of liquid come out but thats it
Let engine idle for 2 min, if fluid starts to over flow during that time you do have a blown head gasket, nothing else can cause that



When gasoline(H) is Burn with Oxygen(O) in an engine one of the by products is H2O(water)
This is why tail pipes drip water, and exhaust systems rust from the inside out, lol
When you shut off an engine the water vapor in the exhaust system condenses back to liquid water and settles in the low spots
When engine is restarted and exhaust warms back up the liquid water is vaporized again and comes out as white smoke, but that should clear out after a minute or two
Starting and stopping an engine after just a few minutes builds up more water in the exhaust system, so you would get quite a bit of white smoke if letting run longer to get exhaust hot, but as said once exhaust gets fully warmed up it will be gone

Coolant leaking in from a bad head gasket keeps adding more liquid to the exhaust so white smoke is continual, also smells "sweet" like coolant
Bad head gasket can also cause the back fire and rough running

 

I went through firing order one more time everything correct, did the WOT test all it did was crank never turned over or tried to. I took the third party IAC off. Put the original part back on, unplugged MAF and it idled perfectly. Replaced MAF went back to running like ****, unplugged the new MAF ran beautifully. Now I’m thinking defective part or vacuum leak? Once again thanks a lot for the consistent replies.

 

MAF(mass air flow) WEIGHS the in coming air, that's what the "mass" means
Computer already knows exactly how much air is coming in, it is programmed for a 4 Liter engine, so at any RPM and throttle position its a simple calculation(for a computer) to get the exact volume of air being used by the engine at any given time

Air fuel ratio for a gasoline engine is 14.7 to 1 and this is a WEIGHT RATIO
14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline

Gasoline's weight does not change much, cold or warm
Air's weight changes A LOT by temp(hot air rises because it lighter) and by elevation above sea level, a liter if air is lighter in Denver vs LA
So that's what the MAF sensor is for, weighs the in coming air
But it only samples 10% of the air as it passes by the sensor part, so even a small error is multiplied 10 times by computer, so can make a big difference

These rarely fail but rarely is not never
And in a 2002 model MAF sensor with 6 wires the air Temp sensor(IAT or ACT) is also in there
Unplugging the MAF sensor puts the computer into Open Loop, so if engine runs better that doesn't always mean the MAF is the issue, computer also doesn't use O2 sensors in Open Loop
Computer is running air/fuel mix tables in memory when in Open Loop, not doing "on the fly" air/fuel mixes
So its a double edged sword when you unplug the MAF sensor, could be bad MAF but could also be computer or another sensors is the problem, its not a definitive test

This is when an OBD2 reader comes in handy to view Live Data from the sensors
You can see the MAF data, the air temp data, the O2 data in real time, same as computer sees it
The Bluetooth OBD2 readers like the ELM327 are $15 and the Torque Pro APP for your phone is $5
Way cheaper than any new sensor
And works on ANY vehicle 1996-2024 sold in US or Canada, its the law, so not a Ford thing