'04 3.0 Problem

[BeeEl]

Hey to all. Following is my problem. Thanks to all in advance for any help.

The check engine light was on. According to my HP Tuners Scanner the code was P0306. I pulled all the plugs and did a compression check. The lowest was 150 and the highest (cylinder 6) was 170. Since the code refers to cylinder 6, and it had the highest compression, I continued troubleshooting.
Firing order was correct
I put the plug in a different hole. No difference (side note: all plugs were installed brand new a month ago. They all still look brand new except 6 which is pretty black)
I swapped plug wires with a different one. No difference
I swapped #2 and #6 wires at the coil. No difference
I unplugged coil and turned it over several times. Pulled #5 and #6 plugs to compare. Neither were wet, which I found odd, but the engine was still pretty warm so I thought maybe the fuel on the plug(s) may have evaporated while I was removing it. Since they were the same, I moved on.
I then began to look at the injector which is new, by the way. We changed that a few weeks back trying to get rid of the code.
I noticed this time that the plug for the injector was not OEM. Both wires were black and were SOLIDLY spliced onto the factory wires. I had no doubts about the splices being good, but I thought maybe the metri pack end might have a problem. I got a new one and put it on.
I put everything back together and cleared the code. The light did not come back on (and still hasn’t).
So we took it for a drive. Seemed to do well until about 5 minutes into the drive. The light began to flash. At any time the light flashes, if you give it any throttle, it does the stumbling with zero power thing. It seems that if you get on and off the throttle, it helps it clear up, but that may be my imagination. This always seems to happen when coming out of a dead stop, but will occasionally do it while driving at speed but that is rare.
I came back and hooked the laptop back up to it. It showed no codes. I’m guessing that is because the light wasn’t staying on? I did notice there was a PID I was monitoring called Fuel System #1 Status (SAE). When it was running right, that PID would read CL-Normal and when it would mess up and the light would flash, it would read OL-Fault. I can only assume the CL/OL is open loop/closed loop. If you sat and watched it for a bit you would notice the light would flash and then go away, then come back, etc. So I began paying attention to that. I opened the TPS to 20% and kept it there. The Fuel System Status would go to CL-Normal for exactly 15 seconds, then go to OL-Fault for 30 seconds and then back, etc… Maybe the intervals would be different at a different TPS%, but that was at 20%. The flashing check engine light corresponded with the OL-Fault. The problem is I don’t what that OL-Fault even means nor do I know if it is the cause or effect of something else. Unfortunately, I can’t read the PCM piece that tells me what takes in and out of closed loop. (not supported by HP Tuners)
Somewhere in the middle of all this, I did a driving test with the fuel pressure gauge hooked up. It maintained 65psi the whole time, even when it was “messing up”.
I also cleaned the MAF with MAF cleaner as well as cleaned the throttle body.
The check engine light never did come back on steady and stay on. However, I show DTC of P0306 (pending).
All I know to do now is get a gallon of gas and a match, but it has now become a personal challenge. I’m hoping someone else finds it a challenge as well because I’m running out of ideas. Maybe new PCM?

 

[BeeEl]

bump

 

[RonD]

Missed this first time around

The higher pressure in #6 in compression test may indicate a leaking valve stem seal, the oil is doing a "WET test", which always increases compression numbers.
And the blacker spark plug tip in #6 would also indicate that
OR a leaking injector, gasoline seals rings almost as good as oil will on WET test

But the DRY spark plug tip should taking leaking injector off the table??

There was a TSB for the 2004-2006 3.0l Rangers
There was a batch of bad valve seats installed in these heads so they would cause intermittent issues in compression
TSB here: https://therangerstation.com/ford_ranger_buyers_guide/Ford_technical_service_ bulletin_tsb_05-26-3.shtml

This doesn't read like what you have but it was a known issue

Flashing CEL means engine damage may occur, usually happens when one or two cylinders are misfiring pretty bad
This doesn't set a code

The fact the #6 injector wires were changed means this has been a long term issue on the vehicle
#6 injector should have a Light Green/orange stripe wire that runs back to pin99 on the PCM(computer)
You could test the wire to make sure is not shorting to ground in the harness, which OPENS the injector flooding out #6 and could cause the black spark plug tip

Other than that you are down to the PCM as the problem

The 3 things a cylinder needs to fire
Compression, above 120psi
Spark, at the right time
Fuel, in the correct mix with air

Compression is high enough
Spark is OK, since swapping 2 and 6 didn't effect #2
So fuel is left

You could try a NOID light on #6 that would tell you if PCM or wire is grounding #6 injector out of time

Unfortunately you can't just swap out the PCM to try another one
You have PATS and the HEC dash to deal with


You could try unplugging the Cam Sensor(CPS) and see if engine will start, some engines won't start without CPS pulse
If it does start see if it runs better no misfire in #6, are more misfires on 4, 5 and 6

Without CPS signal PCM may switch to Batch fire injection, which opens injectors differently, keeps left bank(or right) of intake full of air/fuel mix and then each cylinder just sucks in what it needs, so more like a carburetor setup.
This is less fuel efficient than sequential injection, but an injector can fail and engine would still run OK, it would just set a Lean code on that bank because the two remaining injectors have to be opened longer

 

[rusty ol ranger]

Ron is waaay smarter then i am but...

You said it held good fuel pressure even during these episodes?

A bad cam sensor should throw a solid CEL.

Im betting is a ECM issue.

 

[BeeEl]

Ok. I can try to round up a NOID light to test #6.
Speaking of HEC, I tried to go into "dealer test mode" (or whatever it is called). It simply wouldn't do it. I'm sure I just wasn't doing something right.
I don't completely follow the logic on unplugging the CPS because I thought these use batch fire anyway (two cylinders using the same coil), but I will try it anyway - assuming I can find the CPS.
If I'm not mistaken, the red wire that is on the injector is shared among all of them, which is 12V. Each injector fires from a ground coming from PCM which in this case is light green/orange stripe, correct?

Thank you!

 

[RonD]

Batch Fire is for fuel injection, it was used on the original fuel injection computers
In a V6 batch fire would mean 2 injectors on one bank would open and 1 injector on the other bank would open at the same time, then on the next revolution of the crank the other 3 injectors would open, so each RPM it is reversed
This keeps the intake full of the air fuel mix so each cylinder pulls in what it needs when its intake valve opens

If injector #6 was not working then Batch Fire would allow #6 cylinder to keep working, no misfire from lack of fuel

With Sequential injection a bad injector would cause a misfire, with Batch Fire it would cause a Lean code

The Cam sensor has more resolution to fine tune sequential injection since it spins at half the RPMs as the Crank, so computer can open injector when intake valve is open so less fuel is lost on coating the port in the head, all fuel released is sucked into the cylinder, so better MPG

My hope was that with Cam sensor disabled the computer would switch to Batch fire and if it did #6 would no longer misfire so you would know #6 injector or its signal is the issue

But on some engines, 3.0l is one, the engine will not run at all with cam sensor unplugged, as no cam sensor pulse can also mean no oil pump, which would be very bad on a running engine, lol.


Try using this for HEC: http://www.carlogic.org/bg/data/Ford HEC dealer mode.pdf

 

[BeeEl]

Yes, it held 65 psi even in these episodes

Ron,
Gotcha.

That is the document I followed. I never could get "test" to show on odometer. I held the reset for several minutes.

But back to the original issue, it is so strange that is is much much more prone to do it at idle RPM and rarely at part throttle and NEVER does it immediately after cranking up. That is how we have to leave a stop sign from time to time. The most puzzling thing to me is even if #6 is just not firing at all, I would think it would try to get moving even on 5 cylinders. If we are on an uphill, it will roll backwards even with your foot basically on the floor (assuming the CEL light is flashing).
As far as the injector, it is new. However, I know it could still be defective, but the one I pulled out for it was acting the same way so the odds of both being defective sounds like a stretch but possible nonetheless. It is leaning more and more like harness/PCM output.