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  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

Need Help With Engine Hesitation...

  • Thread starter Thread starter tblue
  • Start date Start date Jul 11, 2012

tblue

New Member
May 10, 2010
5
0
2
Tuscaloosa
Jul 11, 2012
#1
  • Jul 11, 2012
  • #1
I have an 04 GT, with 92k.

I purchased the car used. Here are the known mods
3.73 gears, cammed, 78mm TB, Off road H pipe, flow masters, tuner.....

Have had the car since April. The only problem with the car up until now is when I turned the A/C on the idle dropps below 500rpm and would have a hard time idleing.

2 weeks ago I filled up and that's when the problems started. I thought it was bad gas, but the problem is still there with the new tank of gas and after running seafoam through a tank of gas.

The car seems to idle fine, but has a very noticalbe hesitation/stutter under acceleration. It will smooth out some when the car warms up, but the stutter is still there.

I have cleaned the MAF and have driven with it unplugged, but the problem is still there.

I have cleanded the IAC and TB.

I replaced the fuel filter as well.

One thing I did notice is after I cleaned all these components, the car really ran well, I assume it was because of all the spray in the TB and IAC I used, but once all of that burned off the hesitation/stutter returned.

The car idles fine and revs fine,...it seems that from about 10%-50% throttle the hesitation happens, but anything about 50%-WOT it runs strong.

Maybe bad TPS?

Any ideas what I should check next?
 

jdviper6

Member
Mar 5, 2011
53
1
19
Kenosha,WI
Aug 12, 2012
#2
  • Aug 12, 2012
  • #2
I'm having the same problem. Sorry I'm no help.
 
K

Kilgore Trout

Fried or Broiled ?
10 Year Member
Mar 30, 2005
4,749
95
134
Aug 12, 2012
#3
  • Aug 12, 2012
  • #3
Have you looked at the spark plugs?
 

GOKBGO

Founding Member
Aug 17, 2002
285
0
17
I got....."No boundaries" :-)
Aug 12, 2012
#4
  • Aug 12, 2012
  • #4
Might be a bad coil-on-plug.
 
J

jibloni

Member
Oct 27, 2011
44
2
8
Sep 4, 2012
#5
  • Sep 4, 2012
  • #5
Has the EGR been deleted and have you gapped your spark plugs. Also how big is the cam you have in it, has it been tuned on a dyno.
 

ProchargeMe

New Member
Sep 4, 2012
2
0
1
Sep 5, 2012
#6
  • Sep 5, 2012
  • #6
Do a compression test, check for vacuum leaks, and check your catalytic converters.
 

jdviper6

Member
Mar 5, 2011
53
1
19
Kenosha,WI
Sep 10, 2012
#7
  • Sep 10, 2012
  • #7
I need to check all of the above, how do you check catalytic converters?
 

ProchargeMe

New Member
Sep 4, 2012
2
0
1
Sep 12, 2012
#8
  • Sep 12, 2012
  • #8
Tap on them with something and if it sounds like there's something rattling they are likely clogged up. I had a similar problem on a 94 gt. Replace or cut your cats off.
 
J

jgressley2003

Founding Member
Sep 21, 2002
73
0
7
Indiana
Sep 15, 2012
#9
  • Sep 15, 2012
  • #9
Do you have a check engine light on at all?
 

jdviper6

Member
Mar 5, 2011
53
1
19
Kenosha,WI
Sep 18, 2012
#10
  • Sep 18, 2012
  • #10
Nope, just feels under powered.
 

Matt1323

New Member
Sep 8, 2012
6
0
1
Sep 23, 2012
#11
  • Sep 23, 2012
  • #11
Check your coils...Fords engine seem to have week coils. I was having the same problem for about two weeks and just yesterday i changed them all out and the problem went way. i went with accel coil on plug... andy's auto sport has them for $200 a pack
 

trinity_gt

10 Year Member
Jan 31, 2003
3,125
81
99
Canada
Sep 23, 2012
#12
  • Sep 23, 2012
  • #12
jdviper6 said:
I need to check all of the above, how do you check catalytic converters?
Click to expand...

Your mod list says you have an off-road midpipe which means it has no cats.

You might want to check the O2 sensors. 10-50% throttle is still likely in closed loop so lazy or slow sensors could result in the car running goofy. Once you get into power enrichment the PCM goes open loop and basically ignores the feedback sensors.
 
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