Rough idle? Check your Power Control Module (PCM) relay

My 3.0 liter V6 Ranger (1993) has had an intermittent rough idle since
early 2012. I have read numerous forum posts on the problem, replaced
many parts (IAC valve, mass airflow sensor, coolant temperature sensor,
air charge temperature sensor, and both oxygen sensors). Some parts
were replaced to help my Ranger pass a smog test.

Some of these replacements seemed to help somewhat. I thought I could
live with the sometimes rough idle, which was unpredictable except for
one instance: driving through the pickup lane of a local McDonalds,
which I visit several times a week on my way to work.

Then I took the truck to a shop, one I trust (Auto Repair Master, Oakland,
CA), for a seemingly unrelated problem: diagnose and fix an intermittent
cranks, no start problem. Before I took the truck in, I replaced the fuel
pump relay (which made no difference), and checked fuel pump pressure,
which was good.

The shop kept the truck over a long weekend and reported an intermittent
problem with the PCM relay, and replaced the relay. Result: the idle is
smoother, as is the engine throughout its rev range (and more power). My
Ranger has been running very sweetly since the repair, 9 days ago. Best
$124 I have ever paid for a repair!

I learned that the PCM relay signals the fuel pump relay to activate
the fuel pump. I kept the old relay and intend to check it with a volt-ohm
meter, and compare it with the new one.

 

I replaced my plugs and my 3.0L smoothed right out, but then came back a couple of days later. I plan on a full tune up in the next couple of weeks. Hopefully, that will take care of it.

 

Check fuel trim.
If idle shows +on the high side your lean.....vacuum leak.
If idle shows + on the 2500 rpm you have

Lack of fuel
Too much air
Under reporting sensor

Lack of fuel......pump weak.....filter clogged.....injector clogged.....injector bad
Too much air......egr valve stuck open......intake leak......
Under reporting sensor......can look like anything....usually lean condition

Elm 327 wifi Apple......obd2 fusion
Elm 327 blue tooth....android.....torque pro.
$20 total cost for advance diagnostics.....

Computer compensates and smooths things out. That how it's designed.
Plugs and wires.....sometimes......i guess.

My rough idle was caused by #4 injector bad. I ohmed out all injectors and found that one had no resistance. The coil inside the injector was broken.
Used injector and the truck ran fine.

I also added the zip ties to the throttle cable. I conformed it was not opening all the way and lost power

 

My Rough idle was due to all the exhaust valve seats being bad....New heads no problem

 

I just got a 94 2.3l a few weeks ago, and the thing ran like crap unless the MAF sensor was disconnected. So I did all the basic things looked for vacuum leaks, checked all the gaskets and seals, clean and the replaced the MAF sensor. All to no avail.
Well 2 weeks later after checking and rechecking, researching and just plain pulling my hair out and banging my head against the damn truck. I come across a Video, a video showing where the PCV valve is located. I was like well I never did see it anywhere after thinking about it, so I watched it to find where it was. This thing is buried behind and under the intake manifold.

I find it and see that its disconnected, I thought I did that when I was messing with all the vacuum lines and other hoses coming off the manifold. I pulled the valve itself out to inspect it, boy was it dirty. Not the dirt of sucking in oil or being used for years, but loose dirt and grim from the motor. I cleaned it out, gave it a shake for that rattle sound and put it back in, reconnected the bottom line to it. Then reconnected the MAF sensor, and OMG the damn thing purrs like a kitten now. ARE YOU F******G kidding me i yelled. $200 in parts later to find that a $5 dollar disconnected part was to blame.

So for future reference check that damn PCV valve that thing is a killer.