The truck had idle problems for some time, occasionally shutting down at a stop, and lately speeding up in rpm with my foot off the pedal, but as to acceleration it had plenty of power with no hesitation, or lag whatsoever.

Current problem:
I had driven into town, made 4 stops, and it started and ran fine each time, then drove 25 miles at 60-70 MPH, with plenty of power, excellent acceleration, and no roughness whatsoever, got home and shut off the key. The next day I tried to start it, and it but it just surged, and shook, but wouldn’t run, and I got Codes P0107 lean, P1506 IAC over-speed error, and P0453 EVAP ECS sensor High.

Due to the P1506 code, I replaced the IAC valve, and got the engine to run, and it ran fairly smooth at idle, ran strong when increasing RPM, but when I took my foot off the pedal, it abruptly quit, and would not restart immediately.

The fuel pressure was 55 PSI with key on engine not running, and 60 PSI running at idle.

I subsequently, cleaned the MAS sensor, replaced the EGR valve, replaced the TPS Sensor, and also, replaced the Fuel Cap, due to the P0453 Code.

Now the engine runs, but with a fairly rough idle, and the acceleration is terrible, as I can push the pedal to the floor, and it lags as though the brakes were on, and the Code Reader is giving the same codes as at the beginning, 0107, 1506, 0453, but no misfire codes.

I’m at a loss, can this all possibly be due to a vacuum leak???

 

I would put away the parts shotgun. You have fired it too many times already.
Loss of power in most cases can be caused by fuel supply problems. If the filter is clogeed, pump weary, pressure regulator out of
whack, or the inlet to the pump clogged.
You had it running fine, and it was slow and cranky when it next was used. The IAC, TPS, and fuel cap likely did not wake up and
decide to throw a tantrum ovenight.
I would check fuel PRESSURE, pressure with the regulator disabled(pull the vacuum line and put a finger over the end), and
FUEL DELIVERY volume. Pressure can be high, but as soon as the block is released, it will drop quickly, and may or may not
be delivering fuel in volume. Measure volume for 15 seconds, do some math, calculate volume in GPH. I think 6 is good, but
you should check. If low, could be pickup filter in the tank, pump, fuel filter, failing fuel lines. Pressure should bump if the
vacuum line is pulled from the regulator.
Did you look up symptoms for a P0107 DTC?
tom

 

Thanks for the reply.

The fuel system on my 2.5L is a single line with no return, so there is no Pressure Regulator at the engine location; but the fuel pressure, at the rail, is a consistent 59 psi while idling, so not likely that fuel starvation can be causing the rough idle, and there are no misfire codes.

Stated symptoms for P0107 are numerous, most of which I've already addressed, such as dirty MAS AF sensor, faulty IAC Valve, and faulty TPS Sensor, and it's hardly likely that the fuel filter, or lines could become clogged overnight.

I'm also getting a P0453 code, "Evaporative Emission System Pressure Sensor/Switch High", but I'm not sure how that could cause a rough idle, or decreased power condition?

I'll try a smoke test to see if there is a minor vacuum leak somewhere.

 

I just remembered a F150 that had a rough idle. The one thing I did not check was the vacuum to the power brake booster.
You might try blocking the large vacuum line to see if the diaphragm is intact inside the booster. It was a noiseless leak.
The deal with fuel supply is that a liquid contained in a volume can have the pressure increase easily as the fluid will
go no where. Once you let the fluid flow, the pressure will drop quickly if the flow is impeded, which is why you measure
delivery volume.
Have you tried climbing a long hill? That will in many cases expose a poor fuel supply that cannot keep up with demand.

Do you have hesitation when you try to accelerate? Many times a failing MAF will cause poor acceleration as it cannot
measure the air flow accurately, and the fuel mix gets off causing lean. If you unplug the MAF, you may find your problem
condition is covered up as the ECM will use 'guestimated' values when it loses the MAF input. The values may be a lot
closer than what the flow meter thinks is happening.
tom

 

One of the symptom's other than the rough idle is extremely poor, lagging acceleration.
I did clean the MAS sensor , but I did not replace it.
I have a new MAS sensor, including the housing, on hand, but I've been hesitant to install it without being sure it is the problem.
Maybe, I should try it? Throwing another part at it can't hurt anything but my pocketbook.

 

DID YOU READ THIS:

Do you have hesitation when you try to accelerate? Many times a failing MAF will cause poor acceleration as it cannot
measure the air flow accurately, and the fuel mix gets off causing lean. If you unplug the MAF, you may find your problem
condition is covered up as the ECM will use 'guestimated' values when it loses the MAF input. The values may be a lot
closer than what the flow meter thinks is happening.
tom


Unplug the MAF. The computer will use defaults. If it improves, try the new one. If the new is non-OEM, it may not
work so well. Actually a used one from a pick your part may even be better than an off-brand.
Can you read?