2004 ford ranger Edge cylinder 4 misfire on idle only - Ranger-Forums - The Ultimate Ford Ranger Resource

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Old 07-27-2017
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Join Date: Jul 2017
Location: Mississauaga
Posts: 4
2004 ford ranger Edge cylinder 4 misfire on idle only

2004 Ford Ranger Edge SuperCab
3.0 Vulcan pushrod motor
New spark plugs and wires
Front pads
Front control arms/ ball joints
Rear drum hardware kit/brake assembly
Right rear brake cylinder
New ebrake cables
New right rear axle seal
C bearing for the differential
Crankshaft position sensor
New Coil Pack
New injectors
New Water pump and gasket kit
New Timing cover/gasket kit
New timing chains

Differential flush / gasket
Coolant flush

I've done a compression test all cylinder tested fine.

Opened the pcm everything good on the circuit board.

The spark for cylinder 4 is intermittent
Cylinder 1 0
Cylinder 2 0
Cylinder 3 0
Cylinder 4 -30
Cylinder 5 0
Cylinder 6 0

That's what the spark looks like
On idle.

I've always had a misfire in cylinder 4 only on idle
For example at a red light if I sit for too long it will misfire but only cylinder 4
It's will stumble for a couple secs with engine light flashing
Then it will stay solid and misfire is gone
A little help
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Old 07-27-2017
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Join Date: Jan 2014
Location: Vancouver, BC
Posts: 9,276
Welcome to the forum

2004 to 2006 Rangers with 3.0l engine had a TSB for recessed exhaust valve seats.
Seen here: Ford Technical Service Bulletin (TSB) 05-26-3

Just a heads up
At idle compression is at lowest point when running, if #4 was even slightly lower compression than the average on cold test you may need to do warm engine test

Try running Seafoam or other injector cleaner in the gas tank
If injector tip is dirty fuel will drip at idle instead of spray this will cause misfire

On the coil pack cylinders 3 and 4 share the same coil in the pack, both spark plugs fire at the same time
Reverse 3 and 4 wires on the coil pack, see if problem moves to #3 misfire

Makes sure threads on #4 spark plug are clean and its wire is routed away from any metal that could cause reduced spark voltage at idle
The two Spark plugs are wired in Series, so one spark is "normal", center to tip, #3 I think, the other sparks in "Reverse", from tip to center, so threads are what gets the spark and sends it to center/wire and back to coil pack.

Last edited by RonD; 07-27-2017 at 12:20 PM.
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Old 07-27-2017
Thread Starter
Join Date: Jul 2017
Location: Mississauaga
Posts: 4
I changed the injectors and tested the wiring
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Old 07-27-2017
Join Date: Jul 2017
Location: Conroe
Posts: 31
I'm having the same problem. I have had the truck almost 3 years, and it's been a constant issue for the last 2. I found that running Seafoam through the brake booster fixes the misfire for a few days.

I am looking online now for a newer set of heads.

Also, I have to keep my left foot on the brake while stopped at a red light... and my right foot on the gas at around 1500 RPM to prevent the misfire.

I used to be able to just put it in park, and rev to around 1k RPM's and it would subside... not anymore.
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Old 07-28-2017
Thread Starter
Join Date: Jul 2017
Location: Mississauaga
Posts: 4
That's the only thing I can think of but for one cylinder to be off spark it's weird
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