Hello all,

I recent started driving my 1994 4.0 5 speed ranger and noticed how only can reach 1800 rpm in 5th gear.

I have to basically be in 4th gear to maintain 65-70 and when I shift to 5th it goes back down to 60. And slowly slows down.

also it feels great at lower speeds and even up hills going 30-35.

let me know if this is normal, I also have 3.27 gears and the truck has 180,000 miles, but it runs nice.

also something to add, it idles at about 600 rpm once warmed up, and when unplugging the right 3 plugs on the coil pack, the engine doesn’t bog down, but does when I pull one from the left side.
Left and right looking at the front of the truck,
the left side exhaust manifold also gets much hotter and quicker than the right.

thanks In advance, and sorry for so much I am just trying to have something reliable for the winter in MA.

 

Fords with Coil Packs use Waste Spark system
In a V6 there are only 3 coils in the coil pack
One coil fires 2 spark plugs at the same time
The Matched Pairs on Coil Pack are
3 4
2 6
1 5
front
So 1/5 spark at the same time because both pistons are at TDC, one on compression stroke and one on exhaust stroke, so exhaust stroke spark is "wasted" hence the name Waste Spark System
Actually first spark system ever used on gasoline engines back in the late 1800's, uses Crank shaft timing not Cam shaft timing like a distributor

3/4 fire at the same time as do 2/6

Recheck firing order on coil pack, the 5 6 4 side often gets mixed up, trace each wire on that bank to its cylinder
Ford V6 engine cylinders are numbered like this
3 6
2 5
1 4
front

Because 2 spark plugs are hooked up in series one spark plug fires from center to tip(normal spark) but the other spark plug fires from tip to center(reverse spark)
Either way is the same spark "power"
BUT...........if you unplug the reverse side the normal side keeps on working, if you unplug the normal side BOTH spark plugs stop working, this is why the engine RPMs changes more when you unplug one spark plug on one side vs other side
So unplugging spark plug wires on a Waste spark system is NOT a good test for spark like it was on a distributor


As general maintenance I would pull, clean and regap spark plugs at 0.054" thats spec
4.0l OHV wears out spark plugs pretty fast
And because its Waste spark never use single platinum spark plugs, use regular(no coating) or double coating, single coating will wear out on one side same as no coating, so waste of money

Change fuel filter, ever 5 years
Change/clean air filler

Check exhaust flow, use vacuum gauge, partially block exhaust cause limited power and RPMs
You can also pull out the 2 O2 sensors and go for a drive, it WILL BE LOUD, if engine is peppier then you DO have partially clogged exhaust, Cat or muffler collapsed

O2 sensors are the only sensors that have limited life, 100k miles or 12 years, period, change them if you are not sure how old they are
They only set codes when they are "dead" and at that point you have probably spent $500+ on wasted fuel

 

First off I Thank you greatly

the information on those coil packs definitely makes A LOT more sense to me, ( that explanation was excellent)

Also I will check all spark plugs, might just replace them since I only have put about 300 miles on the truck since I bought it. Air filter looked fine when I checked it but I will definitely change the fuel filter, I’ve also heard that as a culprit for problems.

As for exhaust flow, I will have to test that. Also I will replace the oxygen sensors since they look quite beat up and the actually cracked.

So just a few more things to add to my ever increasing list of things to do to this damn truck.

Anyway, thanks a absolute ton for your answer it certainly helped me understand my own truck

Also since I am currently on vacation for another week or so I’ll add a update eventually.

 

Hello again,

At this moment in time i am wondering and haven’t really gotten anywhere

I have replaced the spark plugs with new double platinum plugs, replaced the fuel filter, put in a new pcv valve since it was only cheap as hell, and put in 2 new o2 sensors

Something I had noticed before this happened was cylinder bank 2 manifold was considerable less hot than bank 1, maybe clogged or faulty injectors?

anyway it’s back to figuring it out

 

And checked coil pack wiring?

You could have clogged exhaust
Pull out the 2 new O2 sensors
Go for a drive, it will be LOUD
If you have more power then you have a clogged exhaust

Clogged injector(s) would cause pinging/knocking when accelerating which you don't mention and would be noticeable

 

Coil pack wiring is correct

I will take out those o2 sensors and go for a drive

Also I just tested exhaust it’s at 19 in of mercury and does move a smidge

will update tomorrow

thanks