I have a 2003 Escape V6 that seems to stumble when I get the car above 40 mph. On top of that it seems like there is something holding the car back from accelerating as the tachometer will climb with the acceleration, but drops back down to around 2000 and the engine will start to stumble or lack the power to accelerate. Below 40 mph (and driving around the neighborhood streets when the tachometer is around 2000), the car seems fine and the idle seems okay. When I got the car home, I used a scan tool and got the (pending) codes P0301 and P0316. My CEL did not come on during the drive and the scan tool doesn't read it as being 'on'. So far these codes are telling me that I have a misfire in the #1 cylinder and a misfire withing the first 1000 revolutions of the engine. So far I have changed out my spark plug, swapped the ignition coil, changed out the fuel injector, cleaned both quick disconnects for the injector and the coil and changed out my upper intake gaskets. Each time doing a test drive of at least 10 miles or more on neighborhood streets and on the freeway I keep getting the same (pending) codes P0301 + P0316 with the same stumbling reaction from the car during the test drive and no CEL that comes on EXCEPT for the last and most recent test drive. The CEL did come on briefly for about 10 seconds and it was blinking, but it went away. By the time I got home and scanned it, the reader was telling me that the CEL was in a 'non illuminated' or 'off' state. Something is telling to look at the wire harness leading to the coil or the PCM. What else am I missing? I am just getting tired of taking of the intake manifold and putting that back on only to get the same fault. Any help would be greatly appreciated.
I would check fuel pressure and delivery volume. Almost sounds as if it is being underfed whenever you get some demand for higher speed. I make the assumption that you swapped one of the COP units to see if the misfire followed, and it didn't. Ditto with the spark plug and injector?
The fact that #1 is the one singled out for tattling by the system does not mean it is the only one. It may just be the strongest of cylinders, and its output is noticed more when missing by the system. I think the crankshaft position sensor CPS, is used to calculate the angular velocity [rotation speed] of the crank after each cylinder fires. When the rpm's drop a misfire is assumed by the ECM. At least that's how I would have done it. So a good cylinder not getting fuel could be called a misfire, but in actuality is not spark related..
Thanks for the quick reply. Technically I did swap the COP however it wasn't to another position, it was for a new one. The same goes for the spark plug and the fuel injector. Since this is a salvaged vehicle, I figured that I change these items so i don't have to worry about them later on. I'll check the fuel pressure. If that doesn't work, could the EGR also be a problem?
The EGR system can give a 'trailer hitch' effect if it is causing the engine to misfire while at speed. Bad plug wires can cause similar symptoms, but you have none. If you haven't, check all the plugs for proper gap. I have seen a picture of the inside of an ECM that was cooked because of misfiring COP coils. I am assuming that a back EMF made the smoke get out. If you can find the EGR diaphragm, you can plug the vacuum line with a golf tee for an experimental run, but don't leave it that way as it will ping.
It wouldn't hurt to inspect the air filter as it could be choking off the air supply when demand increases.