Hello,

I have a 2005 ford ranger 4 cylinder 2.3L 2wd. Recently my engine has been shaking, I replaced all the spark plugs and spark wires hoping that was all it was but it still continued. I checked the errors today and had 14, all were misfires for cylinders 3 and 4. I thought it might be bad fuel but it doesn't make sense since their were only 2 coils misfiring. Is it possible the cylinders are in a series and the ignition coil or coil pack is going bad? Any ideas?

 

What did the old spark plugs in #3 and #4 look like?

Did they show oil or carbon build up?

How many miles on the vehicle/engine?

The coil pack only has 2 coils inside:
Ford uses the "Waste Spark" system
#1 and #4 use the same coil, #2 and #3 use the other coil

So the spark plugs in #1 and #4 both fire on each 1 revolution of the crank, one will be on compression stroke the other on exhaust stroke, so one spark is "wasted"

Same for #2 and #3

I would rent/get a compression gauge and remove all spark plugs then do a compression test.
Write down results

Compression is a fixed result, it can't be intermittent like spark or fuel, so you won't waste your time chasing spark and fuel issues if it is a compression issue.

If you can rent/get a fuel pressure gauge at the same time you can also take off the table, it is another you got it or you don't result.

 

I've got 178,000 miles on it. The plugs all looked okay except the 4th one, it was missing the white ceramic looking internal part. I should go about renting a compression guage

 

178k isn't much for the 2.3l Duratec engine so not a mileage relayed issue.

When doing compression test make sure you hear 4 or 5 "hits" of compression stroke, start at #1 and when removing tester check the end for fuel, there should be some, then clean off the end
When you get 3 and 4 also check, you are looking for possible fuel pressure or injector issue, lack of fuel on the end of tester.

 

My 2000 2.5L had the same symptons and threw code P0303. I replaced the rear coil pack and it took care of the problem. I have 186,000 miles. Soon, I will replace the other coil pack just for good measure. Coil packs for mine are about $60 at RockAuto.com.