I'm having a ridiculous time trying to find the problem with my 2002 4.0 Eddie Bauer Edition. The issues I'm having all seem to be very closely related.

Here are the OBD Scan Results
p0125 (Low engine coolant level
Leaking or stuck open thermostat
Malfunctioning ECT sensor)
p1151 (Lean A Sensor)
p1152 (Rich A Sensor)

Here are the related issues
1. Is running rich, which effects cold starts occasionally, plus wastes gas
2. When Shifting from Park into Reverse, or Park into Drive, or from Drive into Reverse, the car does a huge lurch or surge, probably 1-2 feet. Applying the Brakes almost doesn't stop it (It feels exactly like I'm power braking it
3. When backing in and out of a parking space when I'm having to turn the wheel, the surging happens, and also the car will many times just die, or surge and die.
4. Gas mileage does seem less then stellar (which is probably partially due to it running rich)
5. Not throwing any Check Engine Lights, however, it does occasionally state that the Oil Pressure is low.

What has been addressed so far either by myself/dealership:
1. PCM Upgrade Completed: No change
2. IAC Replaced: No Change
3. MAF Replaced : No Change
4. Fuel Injectors Removed and Sonic Cleaned:
5. Fuel Injectors Flow Tested : No Change
6. Vacuum System Smoke Test: No visible leaks noticed.
7. Thermostat Changed: No Change

The Blue Oval Certified Dealership that I've been working with, is completely stumped, and cannot find the issue. It seems like I'm having problems that have plagued others, but the normal fixes just haven't done anything, and it's really starting to eat away at me. I'm trying to get this fixed up or at least identified tonight.

I have a relatively detailed scantool, via either my laptop or my ipad/iphone.

This forum has been really helpful reading through thus far, but I needed to have a meeting of the minds to help narrow this down. Thank you in advance for any assistance you might be able to provide.

 

P1151 and 1152 are pointing in opposite directions, but both tell you a story about one oxygen sensor and its wiring: the PCM is not happy with what it sees. Connect your scanner and watch the O2 sensors' output: they should normally sweep between 0 and 100, up and down, every 5-10 seconds. If you don't see that, the sensors and/or their wiring have problems. A bad oxygen sensor can cause the rich condition you're talking about, so making sure you have good (and fully functional) oxygen sensors would be a good starting point.

Regarding the surge/sudden death you mentioned, it appears that the engine control unit has a hard time maintaining the idle under variable loads (reverse/drive/park, or extra power required by the power steering pump), so it overcompensates and ends up revving the engine up or letting it die. You said you replaced the IAC valve, so, assuming your new valve works well (did you install a new one, btw?), you could have a problem with the TPS (throttle position sensor) such as a loose contact or bad wiring, thus telling the PCM that your throttle is open when it's not ... which leads to too much fuel for the little air that comes in ... whch leads to rich mixture and rev-ups of the engine.

Again, at this point it is still a guessing game for me, but I would start by making sure that the O2 sensors work well and are read correctly by the PCM. Check them out, replace the ones you found bad (if any), and let us know.

Good luck!

 

From looking at the list of things done ,not many of them seem at least to me, to be related to the problem.
This may not sound appealing to you , but I think a second opinion is in order from a different dealership.

 

The ECT sensor may be bad. If the ECM is being told the engine is cold it will inject extra fuel leading to a rich condition. The the O2 sensors say there's no O2 and the ECM leans out the mix, then the O2 sensors tell it's lean. Have you ever seen dog chasing its tail?

I guess you will find the problem between the O2 sensors, ECT sensor and TPS. And most likely you will find that the parts already replaced were still good.

It is also possible that an ignition problem and or a fuel delivery problem plays into this.

Please keep us posted.