2005 Ford Escape XLT 3.0L V6 DOHC - starts and idles fine. Good power up to about 1500 rpm and then again above 2000 rpm. Problem does not exist outside of this range. Pressing the gas pedal is when the symptoms show up within that range. If I let go of the gas pedal and it is in that range it will not buck. No engine codes show up.

When it is bucking within that range occasionally the Theft light will come on with a notice of no power slightly but the car will keep going.

I have done the following to try to assess and fix the issue with no changes to the actual problem:

- Replaced Fuel Pump, Fuel Filter, ICV (Idle Control Value) and Gasket, EGR Value, Inner Manifold Gaskets, Spark Plugs, Coil-on-Plug Boots, TPS(Throttle Position Sensor), Air Filter and the PCV Valve

- Cleaned Throttle Body and MAF (Mass Airflow Sensor) with the proper cleaner, tried using different fuel octanes and fuel cleaners as well

Have used both a mechanic code reader/live data tool along with my own BlueDriver code reader but nothing is coming up out of the ordinary.

Another thing I have noticed is when I punch down on the gas pedal to the floor in order to gain quick speed I do feel some slight hesitation spurts where, in my opinion, feels like fuel is having issues getting through but you would think that some sort of code would show up.

I'm stumped at this point and instead of throwing more money towards additional parts and taking it back to the mechanic again (they were unable to find the issue the first time) I though I would try here.

 

From what you describe, it does sound like a coil is breaking down when under load, just speculating

 

I did replace the coils along with the spark plugs at the same time and the old ones looked like in good shape but did it anyways. I took a look at the new coils and they all seem to look good. One thing I'm going to do this weekend is try doing a vacuum test to look for any leaks in the hosing and/or gaskets as it seems to be okay when the vehicle is cold but when it starts to heat up it gets noticeably worse.

I'll keep you guys posted!

 

Did you ever check/change the fuel filter?

 

Update .... So i took some time this weekend to try to determine the issue but had no success with getting any closer to solving the issue.

Sprayed some soapy water on the hoses to see if i could locate any cuts or even if there was a change in the running engine but nothing found. Took off a few of the lines to visually inspect them but they all seem to be ok and nothing seemed to be blocking the lines.

As for the Fuel Filter this was changed out at the same time when I replaced the Fuel Pump at roughly 5,000 kms (was still having the same issues with this back then too).

 

One of the things that changes when you change throttle pedal position is the "Throttle position sensor". Before considering replacing it , it can be checked with an ohmmeter if done carefully. You would watch for possible "no contact" or drop out as the throttle is slowly depressed. Before moving on to anything else, this needs to be confirmed working properly..