Engine Intermittent Power Loss Wot

merc123

Active Member
Jan 27, 2003
420
2
39
North GA
www.bluemustangregistry.com
I've had an intermittent power loss issue at wide open throttle and I'm stuck.

I can get car rolling and put into second (1500-1600 RPMs) and stomp it. It will hesitate and stumble a little (normalish) and then accelerate hard like normal. Then you can feel the loss of power all of a sudden (like wheel spin) and it will make a fluttering type sound.

It would clear up and then come back about three times through the RPM range all through the one gear. The car never stops pulling, just feels like you turned the A/C on then off. It is very frequent when motor is colder and more intermittent when motor is at operating temp.

I can half throttle all the way to redline in 2nd gear and it runs fine. Just when you "stomp it."

2003 GT, 123k miles, 3.73 gears

Been through 3 full tanks of fuel from two different stations (Shell and RaceTrac)
  • Replaced EVAP thingy in passenger fender recently (had codes). Replaced hoses also.
  • Replaced gas cap (codes).
  • Cleaned MAF.
  • Checked injectors (ohmed and unplugged)
  • Checked COPs and have spark. Unplugged also to check change in RPM.
  • Checked PCV, it rattles when shaken.
  • Seafoamed it and put rest in gas tank.
  • Replaced fuel pump (Delphi) a few hundred miles ago. Don't remember if changed filter.
  • Unhooked and plugged EGR hose
  • Unhooked MAF and drove, no change.


Motor does use oil and has a blue puff on take off if I idle at a redlight or so. I assume valve seals are the culprit.
 
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wmburns

SN Certified Technician
Aug 14, 2009
5,838
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Suggest having the alternator tested for correct output and excessive AC ripple (bad diode). No excuse to skip this step has almost all auto parts stores will test for free.

What has been done to rule out excessive EGR flow? One method is to disconnect and plug the EGR vacuum line to the EGR valve. Does this make any difference?
 

Jinx

I like cats, cats like me. Cats and I fully agree.
15 Year Member
Oct 2, 2003
11,562
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Cat Country
check for a collapsed or thin elbow tube at the throttle body. They sit too close to the engine and the heat has been know to make the walls thin or burn a hole through them. If the walls are thin and you stomp the gas, they will collapse under the rapid increase in vacuum and restrict the proper amount of air in the system.

I had this happen to my 03 once and eventually a hole developed in the elbow and so much unmeteterd air was entering the system that the car stalled out. I'll post a pic if I can find one.

 
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merc123

Active Member
Jan 27, 2003
420
2
39
North GA
www.bluemustangregistry.com
I'm guessing that's on the front side of the throttle body and goes to the intake tube?

I went ahead and broke down and am taking it to a mechanic that has one of those high dollar Snap On diagnostic computers. Irony is the car ran like a dream there and back. I took it back up there today to leave it with him and it's running fine?!
 
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