I boought this 2000 ranger 2.5 with a bad transmission. It has 129k miles on it. Im not sure how long it sat but I think it sat more than a year because the tags that was on the truck was from 2016. Anyway it always fires right up and runs good for the most part. I got my transmission in and drove it this week to work and home 550 miles this week. I did have3 check engine codes all pertaining to the o2 sensors. I replaced both of them yesterday and the check engine light went out.

Getting new o2 sensors really clear up alot of the missing and rough idle. But it still has a slight miss and a slightly rough idle. I dont know how to move forward as I have no check engine lights to go off of. I dont want to throw parts at it blindly. That costs money. Think it would be worth getting new plugs and wires? Or is there anything else I should check that these motors are known to have issues with?

 

So.i did a little looking at my truck. Turns out #1 plug wire on the forward oil pack wasn't even plugged in. I plugged it in and did a coil pack test I suppose. I unplugged the rear coil pack and the truck started just fine and idles likening always does. Then I plugged the rear coil pack back in and unplugged the forward coil pack and the truck will barley start and hardly idles. So this tells me I have issues with the rear coil pack. So with both coil packs plugged in, I started the truck. And pulled the plug wires off the coil one at a time, and stuck a screw driver down each hole to see the spark. The forward coil pack had strong spark in each hole. The rear had strong spark in 3 and 4. But in 1 and 2 is was real weak. Almost non existent in plug #1. So I'm assuming that back coil pack is bad. I also noticed on the rear coil pack that where you plug it in, the connector was super loose almost feels like it's broke or going to fall off.

 

The 1989 to 2001 2.3l and 2.5l Lima engines have dual spark plugs for extra power, both spark plugs fire at the same time to get the extra power, there is NO alternating, lol

Benefit of dual spark plugs is extra power
Drawback of dual spark plugs is you can never tell if a spark plug is bad until BOTH spark plugs in the same cylinder are failing/bad

So do this test once a year, or now in your case
Unplug the 3 wire connector on one coil pack, and move it away from coil pack as it can arc
Start engine
These Lima engines ran and run just fine on 4 spark plugs, did so from 1974 thru 1988 with a distributor
See if you have a steady miss or miss's, that means at least 1 spark plug on the working coil pack is bad or its wire is
REV engine a few timers, you CAN drive it this way as well, as said millions of miles were driven on these engine with just 4 spark plugs

Then reverse it, plug that coil pack back in and unplug the other one
Restart

If engine runs smooth with either coil pack then not a spark issue

And you can move on to compression or fuel

 

I bet we was typing at the same time. Lol