• Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SVT Tech Forum

rough idle and very slight miss

  • Thread starter Thread starter JDavis83
  • Start date Start date Jun 16, 2018
J

JDavis83

New Member
Jun 14, 2018
1
0
1
Peoria IL
Jun 16, 2018
#1
  • Jun 16, 2018
  • #1
ROUGH IDLE (slight miss)
<<<steps taken>>>
1.o2 sensor Bank 1 sensor 2 (donstream) and New MIL o2 sensor deletes added in place of old ones due to CEL code thrown
2.Oil Changed Mobile 1 5w20 with mobile one filter
3.Spark plugs motorcraft platinum (originally gapped at .54 then regapped at .45 to improve spark)
4.Throttle position sensor (TPS) swapped
5.Intake Air Control (IAC) swapped
6.Coil Packs (motorcaft) swapped
7.Wires (MSD 8.5mm) swapped
8.Mass air swapped ran worse so swapped back
** Discovered gas was in oil and fumes were recircualting back into intake from PCV causing idle to be worse
9.Injectors (Accel 24#) swapped
10.new upper plenum gasket
11.cleaned upper intake and all channels
12.IAC adjusted (raised) by 10% and adjusted throttle body to rise low idle from 675rpm to 750-800rpm
13.Compression Check... all were perfect and extremely close tripple checked
(1=179, 2=180, 3=180, 4=180, 5=180, 6=180, 7=180, 8=179)

others issues that need tending to...
I've owned the vehicle for 2 weeks. previous owner had cleaned the throttle body and washed out the coating inside the throttle body and adjusted the stopper screw (I could tell cause the blue Loctite was missing and I could see where the threads had pliers taken to them. also the intake tube is permanently bent due to the stoke intake tube being partnered up to a fender well cold air. any suggestions would be appreciated. I've exhausted so many options and so much time in the past two weeks I'm losing my mind. what else could it be. noticed a small pool of oil in the lower intake when upper was taken off. I got deal of a life time on the car and now its turning in to an average priced cobra at this point after all the money invested.
 

bret@pastreets

Founding Member
Jun 19, 2002
148
0
16
Lansdale PA
Aug 23, 2018
#2
  • Aug 23, 2018
  • #2
Vacuum leak?
 

BarnStang

Founding Member
Mar 2, 2001
1,260
3
39
Hagerstown, MD
Sep 24, 2018
#3
  • Sep 24, 2018
  • #3
What about the lower intake gaskets? It does sound like a leak. My bet was on coil paks and wires but you covered that...unless I missed it-what year cobra? Hopefully you dont have to deal with IMRC plates...
 
You must log in or register to reply here.

Similar threads

M
Help! 2003 GT misfire when hot
  • Modular03
  • Feb 10, 2026
  • SN95 4.6L Mustang Tech
Replies
4
Views
379
SN95 4.6L Mustang Tech Feb 13, 2026
Mustang5L5
Tuners come on inside
  • squeak93
  • Feb 13, 2026
  • SVT Tech Forum
Replies
1
Views
250
SVT Tech Forum Feb 20, 2026
squeak93
A
Rough idle - cylinder 1 and 6 misfire HELP
  • austindavies935
  • Jul 24, 2025
  • SN95 4.6L Mustang Tech
Replies
12
Views
702
SN95 4.6L Mustang Tech Jul 24, 2025
gkomo
SURGING IDLE / NO IDLE CHECKLIST FOR 1996–1998 MUSTANG GT (4.6L 2V) - Work In Progress
  • Noobz347
  • Aug 30, 2025
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
0
Views
727
1996 - 2004 SN95 Mustang -General/Talk- Aug 30, 2025
Noobz347
SURGING IDLE / NO IDLE CHECKLIST FOR 1999–2004 MUSTANG GT (4.6L 2V) - Work In Progress
  • Noobz347
  • Aug 30, 2025
  • 1996 - 2004 SN95 Mustang -General/Talk-
Replies
0
Views
885
1996 - 2004 SN95 Mustang -General/Talk- Aug 30, 2025
Noobz347
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SVT Tech Forum
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?