Originally Posted by KnockingDiesel
I ran into a similar problem, it was a harness under valve cover. I was going to CO. it was rough idle and low RPMs, but good above 2000rpm. the engine needs the computer to run at low rpm but mechanically over comes it at 2000 rpm and above. hope this gives you an idea.
The engine absolutely needs the computer through the entire RPM range brother. The computer is actually one of our limiting factors in gaining higher RPM's in performance applications.
Who told you otherwise?
I know that it isnt the harness. At least its very unlikely as I just replaced them with new ones and they only have about a thousand miles on them or so. And this is a 550 with 4.88 rears so i hit 2k RPMs at about 55 mph and I run it at about 70 usually.
Codes that I pulled were P0472, P1209, P0603, P1211, P1212, P0732, P0541, P0237, P0541
And that is pulling the codes once then clearing them driving another hour or two and pulling them again.
It has to be something so simple!! Grrr its killing me!!
P0237 - Turbo Boost Sensor A Circuit Low Input / MAP sensor code, might come into play here.
P0472 - Exhaust Back Pressure Sensor Circuit Low Input / I'd probably ignore this, it won't cause the issue you're having.
P0541 - Manifold Intake Air Heater / Ignore, nothing to do with this issue.
P0603 - Internal Control Module KAM Error / Ignore this code anytime you see it. It's caused by resetting the PCM with a hand held tuner more often than not. Not an issue in any case.
P0732 - Gear Two Ratio Error / Are you having trans issues?
P01209 - Injection Control System Pressure Peak Fault / ICP was to high for to long, might come into play.
P01211 - ICP Not Controllable - Pressure Abow/Below Desired / Self explanatory, it's having issues controlling ICP.
P01212 - ICP Voltage Not at Expected Level / IPR code, think we found the culprit.
First, just because you replaced the UVCH's doesn't mean they aren't the problem. More often than not the problem isn't the harness, it's the connector outside the valve cover. It's poorly designed and will loosen up on you. Ford has a wedge that fits in the connection and holds the safety to keep a tight connection. If they're not already installed, you can pick 'em up at a dealer. Or, do a search for the "50 cent mod" and you'll be in business for the price of two quarters.
Now, I think your problem is almost definitely IPR related. The IPR is on the HPOP. HPOP is under the fuel bowl. The IPR threads into the pump, at the bottom of the pump, on the drivers side. There is a two prong/two wire connector going to the brass solenoid on it. The brass solenoid has a stamped brass nut holding it to the IPR. Make sure this nut is tight, and make sure the two prong connection is clean and undamaged. I think that your brass nut has backed off the solenoid and is messing with the voltage.
As for the MAP sensor. During acceleration, the PCM will look at the MAP for a fuel to boost reference. If it's not seeing boost through the MAP, the PCM won't command more fuel to match acceleration and throttle position. This could cause the hesitation and stumble you're reporting. So, check the wiring harness and connector to the MAP sensor as well. I don't think they're very expensive, so if there's nothing visually wrong with your IPR, replace the MAP sensor.