03 Explorer just lacking normal power when warm.

[kryhavoc]

Gents,

I have a 2003 4.0 SOHC that i have recently completed timing chain surgery on. Engine is back in and works with no codes at all. Now that i remembered the coil is 123 465 for the wiring. Dumb mistake on my part which had me chasing a misfire for far to long for my ego.

Codes were cleared and KAM was cleared twice with complete driving cycles between them in an attempt to get the computer to relearn the engine.

Now on to driving results. When the engine is first started in the morning cold the power off the line and through the gears seems normal. Once the engine reaches operating temp it seems to be "lacking" something in the lower RPM range. I swear it feels like my 98 Cummins diesel truck did when i had driven it in town on too many short trips. I had to take it out on a longish drive (45 minutes or so) and really heat it up to blow the carbon out of it and wow... back to normal. Thats what this explorer FEELS like to me today and yes for giggles i did try the "Italian tune up" i read about on these forums.

I have the Forscan program and an OBDII scanner with graphing capabilities and have looked at everything and maybe i am blind but i can't really see anything wrong.

I have replaced/cleaned/worked on the following very recently mostly as a result of pulling the engine and replacing all the timing chains.

New Platinum plugs - Autolite and gapped correctly
New 8mm silicone sparkplug wireset
New air filter
New driver side catalytic converter (and successful back pressure test)
New knock sensor
New EGR valve (old one had a blown diaphragm)
Replaced the coil pack with a junkyard sourced one... it was very new looking
Cleaned the intake manifold runners and IAC valve while they were off.
New PCV valve and rubber tube
New Intake gaskets and i tested for leaks with intake cleaner and watching the OBDII graphs.
Cleaned the original MAF sensor then replaced the MAF with a cleaned junkyard sourced unit.
Replaced the Crank Position sensor
Replaced the DPFE EGR sensor.
Fuel pressure checked... 65Lbs and very steady looking on my new guages
Compression test completed and 170Lbs across the board for each cylinder.
Cleaned the fuel injectors in a bath of berrymans fuel cleaner for about a week.
Replaced the thermostat housing with new 195 degree thermostat and all gaskets. I did reuse the ECT sensor but it does not leak at all and reads the expected 196 degrees when engine is running.
I probably have other stuff i have worked on but left off this list.

I am positive i have an issue left that is holding the engine back from producing normal power when it is at operating temp... but i have no idea where to look anymore. Any thoughts would be appreciated.

 

[kryhavoc]

I should also mention the previous owner said he changed out all four O2 sensors in response to an O2 heater ciruit failure code. When i removed them to look while the engine was out they were all Bosch and fairly new looking and checking the wiring harness proved that i had a common power wire fault causing the O2 heater circuit code. That was fixed before any of this started.

What should ST and LT fuel trims look like on a normal engine? Mine run near zero on the ST... with fluctuations while driving that stay within 8% of zero most all of the time.

 

[swshawaii]

Engine is back in and works with no codes at all. Now that i remembered the coil is 123 465 for the wiring.

^ No misfire codes, so this has to be typo, yes?

 

[kryhavoc]

No, just not clearly communicated on my part.
Looking at your picture of the coil wiring
cylinder 1 (black) cylinder 2 (darker pink) cylinder 3 (light green) <--- i got this right
cylinder 4 (light pink) cylinder 6 (light blue) and cylinder 5 (purple) <---- i wired cylinder 5 to the light blue hole on the coil pack and cylinder 6 to the purpler hole...

 

[swshawaii]

#4 and #6 wires mixed up on YOUR coil?

http://www.explorerforum.com/forums...replace-of-fuel-injector.410088/#post-3310309

 

[imp]

#4 and #6 wires mixed up on YOUR coil?

http://www.explorerforum.com/forums...replace-of-fuel-injector.410088/#post-3310309

Regardless of that, here's what I've just recently found about HO2S "Heater Resistance", which I got both banks, both downstream, both simultaneously. P0054 "HO2S Heater Resistance Bank 1 POS 2", and P0060 "HO2S Heater Resistance Bank 2 POS 2".

Wiring and O2 sensors heater resistance spec: 3 to 40 ohms. My upstreams measured 5 ohms, downstreams 9 ohms, replaced anyway, due to 153K miles. Same codes. Went searching. Unmetered Air leakage. Between MAF and cylinders, somewhere, can cause PCM to throw these codes. I realized suddenly, I had removed and replaced Throttle Bodies a number of times using the old gasket over, which appeared OK. Today I installed a new one. Tomorrow will tell the tale! imp

 

[kryhavoc]

so... a smoke test... i'll do that.

but outside of a leak..... what should ST and LT fuel trim numbers be?

 

[kolb]

I'm having the same problem with mine (02 4.0) so I hope you find it. I'll be watching this thread and if I find the problem first, Ill let you know what I found.

 

[plasticseng]

so... a smoke test... i'll do that.

but outside of a leak..... what should ST and LT fuel trim numbers be?

This is a good read on fuel trims:

http://www.longislandcatalytic.com/understanding-fuel-trims/

and another:

http://www.autoserviceprofessional....-works-and-how-to-make-it-work-for-you?Page=3

 

[kryhavoc]

Smoke test found a very small leak near the PCV valve. I fixed it but no change.

On a second note i did fill the truck up with 85% Ethanol since mine is a FFV. The much higher Octane 105+ (i know it varies due to local concentrations and the weather) and cleaning action seems to have helped throttle response a good bit. This tank should be done in the next day or so and i plan on switching back to regular 87 octane. I am curious is performance drops back to "meh" levels or stays where it is now.

 

[imp]

I should also mention the previous owner said he changed out all four O2 sensors in response to an O2 heater ciruit failure code. When i removed them to look while the engine was out they were all Bosch and fairly new looking and checking the wiring harness proved that i had a common power wire fault causing the O2 heater circuit code. That was fixed before any of this started.

What should ST and LT fuel trims look like on a normal engine? Mine run near zero on the ST... with fluctuations while driving that stay within 8% of zero most all of the time.

@kryhavoc Would you be good enough to tell me what the harness "fault" consisted of? This thing's driving me nuts. Sometimes it takes >100 miles driven to throw the DTC, always P0054 "HO2S Heater Resistance Bank 1 Position 2. Car runs and drives fine.

See: https://www.yourmechanic.com/articl...ter-resistance-bank-1-sensor-2-by-john-nelson

 

[kolb]

Kryhavoc - does yours have a slight timing chain rattle at idle? The reason I ask is, my primary chain rattles intermittently. I'm wondering if the chain rattle is being picked up by the knock sensor and the pcm is pulling timing. The retarded timing would cause the truck to be sluggish. Anyone's thoughts?

 

[kryhavoc]

The chains are brand new.... there should not be any rattle. The knock sensor is also brand new. I found the old one with burnt/smashed wiring and replaced it when i had the motor out. I wonder if i could unplug the knock sensor and see if that has any effect.

Does anyone know if the 4.0 SOHC computer would freak out in any way if the knock sensor is undone?

 

[kryhavoc]

@kryhavoc Would you be good enough to tell me what the harness "fault" consisted of? This thing's driving me nuts. Sometimes it takes >100 miles driven to throw the DTC, always P0054 "HO2S Heater Resistance Bank 1 Position 2. Car runs and drives fine.

See: https://www.yourmechanic.com/articl...ter-resistance-bank-1-sensor-2-by-john-nelson

It was a wire that was mostly broken. Vehicle movement caused it to not provide power to the O2 sensors heater circuit (common circuit for BOTH O2 sensors) on a irregular basis which affected their operation... and in turn, the vehicles performance.

 

[imp]

It was a wire that was mostly broken. Vehicle movement caused it to not provide power to the O2 sensors heater circuit (common circuit for BOTH O2 sensors) on a irregular basis which affected their operation... and in turn, the vehicles performance.

@kryhavoc Makes sense to me! Problem now is that only one is being thrown, P0054, have driven several hundred miles with no P0060. The harness is really difficult to get at. I considered lowering the rear mount & crossmember when replacing the 4 sensors, but did not, my hands looked like dog meat when I got through!

What do you think of simply cutting off the heater feed wires at the harness side of the O2 sensor, and at the fuse feeding it and the PCM, replacing those two conductors? Leave the screwed-up connection(s) lay dead in the harness? imp

 

[imp]

@kryhavoc

"Does anyone know if the 4.0 SOHC computer would freak out in any way if the knock sensor is undone?"

A guess: Depends on how the knock sensor communicates with the PCM, and whether there is no communication (i.e., no current flow) until "look-up" advance values prove too much given the existing engine speed/load/temp. at which time PCM retards a bit, watching result, until knock disappears.

Then too, the whims of the designers.........but look at it this way: suppose a knock sensor croaks. Will the system be A.F.U.? Nah. It might throw some codes, though, if you unplug it, which would have to be erased to get rid of the CEL. Just my 2 cents. imp

 

[kryhavoc]

@kryhavoc Makes sense to me! Problem now is that only one is being thrown, P0054, have driven several hundred miles with no P0060. The harness is really difficult to get at. I considered lowering the rear mount & crossmember when replacing the 4 sensors, but did not, my hands looked like dog meat when I got through!

What do you think of simply cutting off the heater feed wires at the harness side of the O2 sensor, and at the fuse feeding it and the PCM, replacing those two conductors? Leave the screwed-up connection(s) lay dead in the harness? imp

For a power wire.... i would do it. For a wire that is supposed to feed a voltage/resistance measurement... i dont know how the new wire would compare to the old and if it threw the data off. I had the engine out so the wiring harness was nothing to replace at the time. Having done it now... i could do it again with the engine in place though... i didn't thin it was too bad.

 

[kryhavoc]

so i think i have a resolution... i have replaced the IAC valve, the driver side B2S1 O2 sensor and i have run three tanks of E85 through the system.... the power isn't perfect but it is so close that i think its fixed.

I replaced the IAC in response to a idle that was running around 1100RPM when 867 was commanded.
I replaced the B2S1 O2 sensor due to what i perceived was a slightly lazy response time.
I ran the E85 because it has a much higher cleaning factor and much higher octane than regular 87 gas.

still working it but i am happy for now at least.