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Help W/ Hesitation Under Hard Acceleration

  • Thread starter Thread starter folky15
  • Start date Start date Mar 18, 2015

folky15

Member
May 10, 2007
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13
Chicago
Mar 18, 2015
#1
  • Mar 18, 2015
  • #1
I'm stumped and looking to see if anyone has a possible solution to this!

2001 Bullitt with 77k miles. Car idles and runs great except when accelerating over 4000 rpm.

Right around 4000 rpm, in every gear, the car hesitates dramatically and occasionally shuts itself off. I've noticed that it also does the same hesitation when I am accelerating and hit a large bump.

I've just replaced the fuel filter and that didn't seem to have any effect on the problem. The fuel pump was replaced about 20k miles ago. Car isn't throwing any codes.

Anyone know what might be causing this?

MAF? COP? ECU? Alternator?
 

COramprat

...I can take it. I think.
20+ Year Stangneter
Mar 2, 2003
8,474
1,463
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Sea of Tranquility
Mar 18, 2015
#2
  • Mar 18, 2015
  • #2
Check the Fuel Pressure sensor. Usually throws a code though.
 

squeak93

15 Year Member
Jun 2, 2005
2,266
364
164
Joplin, Missouri
Mar 18, 2015
#3
  • Mar 18, 2015
  • #3
+1 on a fuel problem. New parts don't mean they are still or ever were working as planned.
 

1987stangman

Member
Jul 12, 2006
684
24
19
Mar 18, 2015
#4
  • Mar 18, 2015
  • #4
I would check for codes anyway. Just because the service engine soon light is not on does not mean there isn't something stored. If no codes start from the basics and check fuel pressure with a mechanical Guage and verify it is within spec then go from from there.
 

Mineral4.6

Member
Mar 17, 2015
76
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18
Mar 19, 2015
#5
  • Mar 19, 2015
  • #5
Im having almost same problem except its all before 3k. once i get past 3k or WOT it runs fine. i originally had a mass air sensor code, changed that out and ran great for a week now its back to same problems but throwin O2 codes.
 

folky15

Member
May 10, 2007
11
23
13
Chicago
Apr 28, 2015
#6
  • Apr 28, 2015
  • #6
Just following up - turned out to be a COP boot that had worn out. I found this by just checking out what was loose under the hood. One of the COP's moved around more than the other ones so I replaced it ($6 part). Worked like a charm!!
I guess the engine vibration above 4k rpm and when going over bumps was enough to shake the COP and cause a misfire.
Hope this helps someone else.....
 

trombonedemon

Well-Known Member
Jun 25, 2009
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U.S.A, U.S.A., U.S.A.!
Apr 29, 2015
#7
  • Apr 29, 2015
  • #7
Thanks for the reply, and solution!
 
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