At My Wits End!

This is on a 2004 Explorer, XLS, 4.0L (FLEX FUEL) SOHC - - - - - -

Here's an update: I thought I'd do it this way instead of starting a new topic.

I have zero psi back pressure on both banks. I blocked every vacuum port on the intake manifold. Still getting a ST Fuel Trim driving Max Lean on Bank 1, because it's too rich. Bank 2 looks better at about 2 to 5%. Have not run it long enough since KAM reset to get any LT Trim results yet. Both O2 Sensors have been replaced. MAF replaced. Cam timing tool set is in hand and that is the next step.

This has certainly been a challenge and I have turned into a Parts Changer! LOL

Thanks, everyone for the great input!




I have Bank #1 - Rich and Bank #2 - Lean Codes! ???? P0300, P0301, P0302, P03

03, P0316 Codes were corrected by replacing the plug wires and cleaning/gapping the plugs. I have new plugs on hand and will replace them, since I'm Shifting into "Parts Changer" Mode.

I used to think I was fairly savvy at diagnosis, but those days are gone! LOL

I have changed the Intake Plenum Seals, Plug Wires, Cleaned and checked Plug gaps, MAF Sensor, will replace Upstream Oxygen Sensors and PCV Valve and Spark Plugs. SES Light flashes after idling for a relatively short time (about 5 minutes), indicating misfire(s). My SOLUS shows the O2 Sensors are switching, but Short Term Trims are maxing out on Bank 1 toward lean and Bank 2 toward rich. We were discussing (and cussing) it at my buddy's shop and fuel injector "Crud" came up, given the vehicle sitting for so long. This might be an "Ah Ha!".

I finally got it licensed and registered, so got on some hard pavement. Floored it and it seemed pretty darned good for a 4.0 with 125,000 miles. That made me believe the Catalysts are okay. I'll check back pressure when I get it on the hoist.

I'm getting ready to "slug it" with LUCAS Fuel Injector Cleaner and then, discovered that it has no Fuel Pressure Test Port (Grrrr!). Fuel Pressure on my SOLUS shows 39.8 psi. and no injector electrical faults. I guess I'll pull the intake plenum again and remove and clean each injector and replace the O-rings. I have an injector pulser and might give that a try before removing them.

This one sat out in the open, on a concrete slab in Northeastern North Dakota for about 2 years, 6 months and started right up with a new battery and PCM. I immediately filled it with fresh fuel. I have looked for wire "Chew Throughs", since I found a nice "Squirrel Habitat" in the upstream side of the air filter.

After the O2 sensor, Transfer Case and Transmission Service, I'm "detail stripping the interior" and will look for more signs of "damage by residents".

Other than all that, it's a fairly clean vehicle, with little rust. I thought the price was right at $500.00. It is still in the "Good Deal" category, given the market prices I've seen around here.

If anyone has ever had this experience, or has any ideas, I would be very appreciative of what you have.

did you reset the kam in the pcm after all the repairs?? your scanner should have it in functional tests

also when is the bank lean?? at idle?? if so raise the rpm up see if the lean bank improves you might have an intake gasket that might be leaking on one side and overfueling the side that isnt...

BOBBA LOUIE wrote:
I used to think I was fairly savvy at diagnosis, but those days are gone! LOL

LOL! We've all had those days! Don't lose the faith. You'll bounce back.

Short Term Trims are maxing out on Bank 1 toward lean and Bank 2 toward rich

What are your Long Term Fuel Trims?

Does fuel pressure bleed of after turning the key off. Can you do an injector balance test?

SES Light flashes after idling for a relatively short time (about 5 minutes)

Is there a, noticeable, Misfire while the light is flashing?

I agree with cheryl about resetting KAM.

Double post removed.

You likely have a breathing problem. One side isn't breathing as well as the other so it confuses the pcm. The side with the rich codes/trim isn't breathing like it should. Plugged exhaust, cam timing, intake manifold runner control. Did the 4.0 have intake runner control? I can't remember.

The MAF reads all the air coming into the engine and the pcm assumes each cylinder is getting equal amounts of air. But if you have a problem on 1 bank then it is getting less air than the computer thinks so it takes fuel away. And the side that is breathing properly is getting more air than the computer thinks so the pcm adds fuel to that bank

I reset the PCM BY shorting the disconnected Negative Battery Lead to the Positive overnight. They drove right back up. Pain in my rear!

I did and the graphs headed toward Zero. That's when I changed out the seals on the Intake. I blocked off the PCV Line at the Port on the Intake and replaced the EVAP Cannister hose. Next, the Brake Booster Line gets blocked.

I'll put it on the hoist tomorrow and will check back pressure on each side when I replace the O2 sensors. The 4.0L doesn't have Intake Runner Controls.

Long terms are maxed out at -25, Bank 1 and 25, Bank 2. Doesn't take long for them to go there after a PCM reset. Problem now is that it's so darned cold up here that I can only be out there for so long before I have to take a "warm break". LOL

Fuel Pressure holds up well. Have not gotten to the injectors. Still trying to get Bank 2, O2 Sensor loose. Had 0 psi back pressure at 3000 RPM on Bank 1, so the right Cat, cross over pipe and muffler are clean. My hands are too big to do much with the Bank 2 Upstream Sensor. At least, the Propane supply got delivered.

I did reset/clear KAM before checking back pressure. Thanks.

I did reset/clear KAM before checking back pressure. Thanks. Misfire not evident.

Great point! When I get the sensor off Bank 1 and check the back pressure, I hope that gives me a better "picture".

I think the EGR valve is on the bank 2 manifold. Pull a hose off it to check back pressure on bank 2

Not sure I replied correctly. I used Quick Reply. The misfire isn't very bad and most times, not noticeable. When I rev it up a bit, SES light stops flashing.

The EGR tube comes off Bank 1 Exhaust Manifold at the rear to the EGR fitting on the Intake on this one. The V-8 must be different. Still working on it. Have/will not give up. LOL

I'm starting to believe there's a cam timing issue, but want to satisfy myself that the left side cat is not plugged.