My son's 96 Ranger has a bad "stumble" under heavy load in higher RPM's (like when you're merging onto the interstate or passing someone). It almost feels like an electrical problem like someone is cutting the ignition off and on quickly.

When we got the truck, I had Autozone pull the following codes:

P0320 Ignition/distributor engine speed input circuit (from what I read this is the cam position sensor) - REPLACED

P0135 O2 heater circuit bank 1 sensor one (mine is broken off so I know why I’m getting this code) - Not replaced yet, but I do not believe this would cause the problems we have

P0401 EGR flow insufficient detected - I believe this is fixed (see my other post on this) as we replaced the EVR and vacuum lines, as well as tested the EGR

P1131 lack of HO2S11 switches - sensor indicates lean (see above re: broken O2 sensor).

We cleaned the MAF sensor (was pretty dirty), replaced the cam position sensor, replaced the EVR (had a broken nipple) and the associated vacuum lines. Also pulled the battery cable to clear the codes (I guess that still works for OBD-II?)

What are we missing? The thing is, the truck starts like a brand new one, and driving around town it drives like a champ, so I don't think it's jumped time one tooth. It just bucks like crazy under load and bogs down fairly quickly on longer grades on the Interstate (I know these trucks don't have a ton of power, but my grandpa has one just like it and it does great on the Interstate).

The only other problem is the idle seems to hang a bit in between shifts, but it is MUCH better now than it was. Maybe it's a little slow to drop by nature...I can't remember on my grandpa's truck if it does or not.

What should we check next? IAC? Could it be a coil pack, and if so, is there a way to test them? Maybe a crank position sensor (although it wouldn't start at all if this were the problem)?

In the mean time, I think I'm going to take it back to Auto Zone and have the codes checked again to see if anything has changed since the last bit of work.

 

On the 1995 to 2001 4cyl Rangers you can unplug the 3 wire connector on a coil pack and then start the engine
Engine should run fine with just the 4 spark plugs working, may have a lower idle and won't have as good performance but will run fine

So do that, drive using just one coil pack hooked up, then do the same using other coil pack
This tests all 8 spark plugs and both coil packs
If you have a misfire running one coil pack then you found a bad spark plug or wire, could be coil pack but probably not

There are myths that float around that sparks alternate or skip, the whole point of dual spark plugs in vehicles is better performance, so BOTH spark plugs in a cylinder fire at the same time and every time.
When engines started to have 4 valves it was better performance than dual spark plugs so this was dropped in favor of the 4 valves
In airplanes dual spark plugs was done for safety, two separate spark system entirely, but also used for better performance


O2 Sensor 1 1 is the upstream O2 so will absolutely effect performance, get it fixed
O2 sensors need to be above 650degF to work, which is why they are heated

O2 sensor 1 2 is downstream, after Cat Converter so not as important to short term operation, but will effect performance over time

Change fuel filter, every 5 years, or if you get stumbling at higher engine loads

On manual transmissions the RPMs should hold for 5 seconds or so with clutch pedal down, then only drop to 1,100 or so
RPMs should drop to 700-800(warmed up engine) only after speedometer is under 5MPH
This is for lower emissions, engines running under 1,000RPMs are big polluters, has to be Rich mix or engine will overheat

One of the biggest headaches car makers have with emissions are cold starts and idling(cold or warm), lol
Newer cars actually shut off the engine when you stop, then restart when you hit gas pedal to go again, you thought that was to save gas...............lol, it actually uses more gas it you are stopped less than 60 seconds.

 

Ok, I will certainly try that with the coils to eliminate them and/or wires and plugs. Also as for the O2 sensors, I ordered two today from Rock Auto so I’ll replace those soon. The upstream one is actually broken off in one section (does not allow an exhaust leak however) but the downstream is ok, or at least hooked up.

As for the idle sounds like mine is ok.

 

If the ignition mod has not been performed, four of the plugs fire on the exhaust stroke and the engine will certainly not run on that coil pack - search "Wasted Spark System". I did have a coil pack fail intermittently on a Toyota Camry and it would buck under load like the transmission was failing, so yours does sound like a coil problem.

 

And another poster spreading the myth.
Both plugs fire on compression and exhaust, all 4 plugs in cyl's 1 and 4 fire at the same time, twice for every revolution of the motor, same for cyl's 2 and 3
Engine will run with either coil pack unplugged.

 

Welcome to the forum


You need to search "Waste Spark"

As 2011Supercab said waste spark MEANS each spark plug fires at every TDC(top dead center) in every cylinder, compression stroke TDC and exhaust stroke TDC, so a spark is "wasted" on the exhaust stroke, hence the name "waste spark"
Ford, and many others, use Waste spark because it is simpler to use when you don't have a distributor.

First gasoline engines made used Waste Spark, so its the oldest spark system, and pretty much all single cylinder engines, like on lawn mowers, use Waste Spark, way simpler to time spark with crank

And no, spark on exhaust stroke is NOT for better emissions, doesn't help or hurt, spark is just Wasted


Totally unrelated to Waste Spark is the Dual spark plugs used in the 2.3l and 2.5l Lima engines
Dual spark plugs were used on a few inline-4 and inline-6 engines, hard to fit them in on V6 or V8 engines, dual spark increases performance, simple as that, so BOTH spark plugs fire at the same time or there would be absolutely no point in having the Dual Spark plug setup.

The advent of 4 valves per cylinder gives better performance than dual spark plugs so they are no longer "in fashion", lol

 

Good info RonD. So is the 2.3 a Wasted Spark system as well as Dual Plug? I have read that the wasted spark is much weaker than the "primary" and I have also read that the electron flow direction of the wasted spark is reversed so it wears out copper plugs quickly.

Autolite Myth Busters: Copper Plugs and 'DIS' Engines

https://www.ngk.com/glossary/8/spark-plug/W

 

Yes, 1989-2001 2.3l and 2.5l Lima Dual plug all used waste spark system
As did 4.0l OHV and SOHC, 1990-2011
And 3.0l 1995-2008

And most Ford models once distributor was gone
Earlier 2.3l Lima, 1974 to 1988, used a distributor and 4 spark plugs

No, on the weaker spark in waste spark
2 spark plugs, in different cylinders, are wired in series, so one will spark normal, center to tip, the other will spark reverse, tip to center.
But the spark voltage is the same on both

With normal spark, center to tip, the tip would wear out faster than the center, that's when Platinum coatings were first used, on the tips.
But on the Reverse spark plug you need platinum center instead of tip

People may have put in single platinum tipped spark plugs and then noticed that 1/2 the spark plugs were wearing out faster than the others, "WTF, I guess with waste spark one spark plug is weaker so spark plug doesn't wear out as fast"
But it's just the wrong coating, so with waste spark go double platinum or regular copper/nickle, skip single platinum

 

…….fuel filter, 02 sensor,the first one closest to the motor, maybe check fuel pressure at the rail...if its fallen a little(fuel pump efficiency declining) maybe its not enuf to support load

 

I drank the Kool-Aid on the ignition mod, but I am coming back to life learning about causes of spark plug wear.

 

With things like the coil pack mod its more about what makes you "feel like its better performance", it doesn't have to actually be better performance

All Rangers with fuel injection came with Cold Air Intakes(CAI) since the mid-1980's
And dyno tests have shown add-on, 3rd party, CAI's don't change a thing, some even make HP worse, lol, but again it doesn't matter, its the idea of it that makes for the better performance

 

The 2.3 Ranger is so underpowered it is like driving a VW bus. I had read that the Lima OHC up to 97 suffered from poor intake flow and a pleated fabric filter (K&N) did help, and there does not seem to be much out there to get it to breathe any better. I had done the ignition mod many years ago and it did seem to run a lot better, but I had also changed plugs, wires and cleaned the MAF at that same time, so I am sure THAT is what caused the improvement. At the time that I tried the mod, there was not a lot of details to confirm what a crock it was. I did see some of the details as to why it would have no effect before my first post on this thread, but it took a while to digest it. I think I really wanted to believe that it would work.

 

This 2.3l engine was first used in 1974 Ford Pinto, it is nick named "The Pinto Engine" because of this

It is heavy and under powered, but it just keeps on running, lol
So its 1970's technology and there has been quite a few improvements in engines since then but....................

Double overhead cams, 4 valves, variable valve timing all have higher failure rates than the old 2.3l Lima, so its a trade off. as it usually is. with better technology

Mustangs used the 2.3l Lima for many years, so Mustang forums are a good sources for power upgrades, what works and what doesn't work
But in the end it is what it is 1974 engine