Having issues with my 1996 ford ranger 2.3cyclinder motor. In the last year I have replaced the iac, tps, timing belt, plugs & wires. If you are working at the motor and you move the throttle cable you can hear for like a split second that the motor is bogs down for a split second and then will pick up to full speed. It feels even worse when you are driving it because when you get on the accelerator it like jerks the truck. If you get off the gas and back on real quick it is really bad almost like a universal is going out, but I know it is not that
. Any thoughts anyone? Any help is appreciated.

 

Wow, that sounds so familiar. That is a known problem on classic VW 009 distributors (commonly referred to as a dead spot). Not sure what you have, and I know it isn't a vw. The cure for vw's was to change springs and weights (not 100% effective) or go with a SVA (single vacuum advance) distributor. Always at the same place, just off idle. Sorry I'm of no help.

 

Check the TPS voltage.
Need a volt meter and a sewing pin to pierce the wires

Key on engine off
Do not remove wires, use pin to pierce a wire to test voltage
Top wire should have 5volts
Center wire under 1 volt, .69 to .99 is spec
As you slowly open the throttle the Center wire voltage should go up, no jumping or dropping of voltage, nice and steady all the way to WOT(wide open throttle) where it should show above 4.5volts, 4.50-4.99 is spec
Open and close throttle a few times making sure Center wire voltage is stable, no jumping or dropping

TPS voltage tells computer driver wants to accelerate or slow down.
Normally the MAF(mass air flow) sensor tells the computer how much air is coming in and so how much fuel to add to intake.
But if you want to accelerate quickly the MAF sensors air flow data would have a slight delay before reporting the increased air flow from throttle opening.

Same problem occurred on carburetors, sudden opening of throttle plate dropped vacuum in carb so less fuel was sucked out of the Jets and engine would hesitate before accelerating, so an Accelerator Pump was added, when you pressed down on gas pedal Accelerator Pump would squirt extra fuel into the engine for faster throttle response until Jets could catch up to engine RPMs.

When TPS voltage goes up quickly computer adds more fuel quickly like accelerator pump did on a carb, allowing MAF sensor data to catch up to engine RPM

 

Great tip RonD!

 

RonD, when I get home I will check this later tonight. Does it seem normal for something like this to be failing even when I'm not getting engine codes?

 

How would computer "know" it is failing?

If it failed outright i.e. no voltage on Center wire then yes, computer would set a code.

But TPS is Driver controlled, so Driver can feather gas pedal or press it to the floor and then release it completely, so voltages going up and down are "normal".
So there is no "comparison" computer can use unless there is no volts or above 5volts.

Now the computer can, and does, compare TPS voltage(throttle position) to MAF air flow and engine RPMs, i.e. if TPS is showing 3volts but engine is idling then it would set a code.

Point being it is possible for TPS problem to not set a code.

And TPS may be fine, but testing is free, so take it off the table so you can either fix it or move on to something else.

 

RonD, I checked the tps this morning, everything checks out to your specs for those instructions. Any other ideas?

 

Thats good.

Next would be vacuum leak.
Vacuum gauge is cheap, under $25 and can tell you a whole lot about engine condition.
Good read here: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine

Works on any gasoline engine.

It can tell you what is happening when you open throttle.

2.3l uses a timing belt which will stretch as it gets older, this can cause a hesitation when you change RPMs under load because cam falls slightly behind crank so compression drops off until it catches up

For a quick test for vacuum leak:
Warmed up engine, idling
Unplug IAC(idle air control) Valve's wires
IAC Valve will close and engine RPMs should drop to 500 or engine may even stall, either is good, it means no vacuum leaks
If RPM stay above 700 then there is a leak

Also when an engine is warmed up and it has an EGR valve, the computer will activate the vacuum solenoid for the EGR when accelerating.
The EGR valve won't cause hesitation but if vacuum hose FOR the EGR valve has a leak then you get the hesitation from that vacuum leak which won't show up on idle test.
Long shot

 

Ok, someone else had already mentioned to me about unplugging the IAC. The rpm's do drop when I do this although the truck never came with a tachometer I can tell the drop low, but never to a point where theatrics will shut off.

I had thought of the EGR valve, but I was told that usually you get very poor mileage when they don't work and I still am getting around 20 mpg. I will take a look at this tomorrow to see if anything shows up. Thanks

 

RonD, I fall had a chance to look at e vacuum. Everything seems to be working, it holds at 19 and when you hit the throttle it spikes high, down to zero and comes back up and holds at 19. Here is a question when I changed the timing belt and I align all the arrows I notice the arrow for the camshaft does not align up perfectly like the book says. I've tried it both ways with the arrow before and after. It seems like when I set it before I don't have the power. Have you ever seen this?

 

I was doing some research online, does my 4 cyl. Have a camshaft position sensor? If so could this be the problem

 

Yes, it will have a CPS, yes, could be the problem.

CPS "reads" AUX gear, turned by timing belt, which is why you need to time that gear

 

Not sure what you mean by timing that gear, do you have any better instructions on this?

 

The 3 gears all have timing marks
Crank gear
Cam gear
Aux gear

Drawing here: https://motogurumag.com/i/routnda-t7...er-WRSMmUW.jpg
And here: https://motogurumag.com/i/ford-23l-l...er-khFEoXi.png

Middle one is Aux gear, it drives the oil pump, and since it is the same size as the Cam Gear it can be timed so a CPS can be used on it instead of actual Cam gear, just easier to mount CPS there

 

Hey, RonD. Been having log in problems so wasn't able to reply. I have the truck running better. After looking at my tinming again, I realized that the oil pump sprocket was not set correctly. Besides the diamond on the pulley there is also a arrow on it as well. I was going off the arrow instead of the diamond. After correcting this I was able the set the arrows for hand camshaft correctly. I have my power back again, although I still get a continuos fast idle every now and then when I come to a stop. Not sure if this is a IAC not working correctly or not.