Truck was running like a champ and blew a gasket which caused engine swap out. Hooked everything up started it and all was well ran great going down the road and sitting in the shop. Next day I started it up and thought it was going to blow up it ran off the tach on RPM's. Switch it off wait a few minutes and visually check it out under hood and start it up again. Now it won't idle at all sputtering horrible and cuts off. I've changed everything I can think of except for the ECM (computer). Anyone have any advice for I would be very grateful and interested to hear what you have to say.

 

Welcome to the forum

I assume a 4.0l engine but Rangers used two different 4.0ls
4.0l OHV, 1990-2000
4.0l SOHC, 2001-2012

Whats your year?

RPMs can only be created by air flow, that's the point of the throttle plate/gas pedal setup used since day 1 on gasoline engines
So "gas pedal" was always the wrong term, it is, and has always been, an Air Pedal

You can feed extra gasoline into the engine and all you will get is a flooded engine, no increase in RPMs, more air is what increases RPMs, more gasoline just keeps engine running as more air is added

So first thing to check is the return spring on the throttle plate, it must be strong enough to close the throttle plate against full air flow into the intake.
And throttle plate must move freely, no binding of the rod or throttle cable to gas pedal(and cruise control, if so equipped)

High RPMs is always an AIR leak, and too much air can also cause Lean fuel mix so pinging/knocking and/or no start

 

Yeah I have checked that first thing and replaced all the sensors that are related to having this type of problem. Any other ideas

 

sensors rarely fail, so bad move, and may be your problem now

"new" used to mean tested and working
"new" now means "you test it for us, and we will replace it if it doesn't work"

You should test sensors when you can, check connector for corrosion, and then replace only as last resort and only that 1 sensor
If new sensor doesn't change anything then replace it with old one, and move on

90% of DIY sensor replacement was not needed
50% of Pro Mechanic sensor replacement was not needed, but most of that is done for "padding" the Bill, not much money in just cleaning a connector, lol

be nice to know which engine you have?
4.0l SOHC has 3 timing chains, 4 if 4WD, very high RPMs can cause one to slip, so one bank of engine will have lower compression after that

Have you tried manually adding fuel to intake for startup?
Gasoline in spray bottle or Quick Start(ether in a spray can)
Called 50/50 test

Tells you if fuel or spark is the issue

If it doesn't start smoothly with fuel added then either spark or compression is the issue
Compression is black and white, mechanical, so best to test first so no wasted time if thats the problem.
2000 and earlier should be 150psi
2001 and later should be 165psi

Used engine?
and I assume no history?

Matching years?


Couple of easy tests
Remove IAC Valve, plug its two wires back in
Turn on key, IAC Valve should open all the way(for starting)
Unplug the two wires, IAC Valve should close all the way
Plug wires back in, and it should open all the way again
Repeat a few times to make sure it is not sticking


Unplug TPS(throttle position sensor), it can cause issues and can turn off fuel injectors
See if engine starts better, TPS is used for quicker throttle response

Unplug MAF sensor, computer already knows its running 4.0l engine so already knows air/fuel ratio at any given RPM, MAF is there to fine turn for air temp and density
See if it runs better


Ranger V6 engines have an oldball coil pack wiring
3 4
2 6
1 5
front

the 5, 6, 4 side gets me every now and then, reverse wires
One of those "I checked it 3 times!!!"
And 4th times a charm, lol.

 

There's an extra timing chain if 4wd??

 

Yes, 2001 was first year Rangers got the 4.0l SOHC and also Live Axle, always locked front hubs, Live axle Rangers were seen as earlier as 1999 but 4.0l OHV(or 3.0l OHV) engine wouldn't have an issue because of less rotating mass

Engineers thought the always turning front drive line may start harmonic vibration with the 4.0l SOHCs rotating mass, so they added a balancer shaft to the 4.0l SOHC for use in 4WD Rangers, counter rotating to offset any vibrations, thats what the 4th timing chain operates.

More than a few have swapped in 3 timing chain engines into 4WDs and reported no vibrations, and visa versa.

So as far as I know it was an "on paper" issue, a maybe that was engineered into the design

 

Hello, i am having the exact same problem as you dricribe only difference is that mine didn't run like a champ on the first start. Mine started rough but wouldn't idle and then a couple starts later it redlined and died immediately. Curious as to if you have found a solution? Thanks.