Hi guys.

I have a '96 Ranger with the 4.0L engine. It appears that cylinder 6 is dead. I get a P0306 code, and it runs rough. Here's what I've tried:

New plugs and wires. No change. Old plug looked fine.

If I pull the plug wire off the coil pack, the engine doesn't run any worse. With any other cylinder, the truck runs noticeably worse with the wire disconnected. On the faulty cylinder, I can hold the plug wire an inch from the socket on the coil pack and the spark will jump the gap so I assume I'm getting sufficient spark.

Compression tester shows 100 psi in cylinder #6; 110 psi in cylinder #5. Both briefly jump to 120 psi while cranking. This is with the engine warm but not hot.

It's getting at least some fuel (I can smell it while cranking during the compression test.)

Emissions test shows HCs off the chart.

Recently got a P1443 along with the P0306; after replacing the evap purge sensor and solenoid, P1443 has not returned.

This thing had a history of occasionally running poorly. It would show multiple misfires for a week, and then run fine for months. I never could track it down, but when I cleaned the MAF, it seemed to run fine until this P0306 started showing up.

I'm not sure what to check next. It's about 10 psi down from the other cylinder I checked, but above the 90 psi minimum listed in the Haynes manual. Oil is not milky or thinned out, so I believe that eliminates the head gasket.

I'm officially stumped. It failed the emissions test (7 times the maximum limit on hydrocarbons), so I've had to park it until I can resolve this. Any ideas would be appreciated. Thanks.

 

Alot of oil into that cylinder?

 

How would I be able to tell? Spark plug is clean, and it's my only vehicle that doesn't consume oil.

 

If you have a good compression reading, (warm, WOT) and a good hot (blue) spark, you need to check the injector.

A smell of gas while cranking is not sufficient to eliminate the injector..

Pull 2 injectors and switch them, if the failure follows the injector...

Either run concentrated injector cleaner (pressure tank) through the rail, or send the injector out for cleaning/replacement.