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How Rough Should A Stock Fox Run?

  • Thread starter Thread starter 2007_Crown_Vic
  • Start date Start date Apr 28, 2017

2007_Crown_Vic

Active Member
Aug 19, 2016
133
26
48
Apr 28, 2017
#1
  • Apr 28, 2017
  • #1
Hi Guys,

Should a stock foxbody run fairly smooth? My 1990 GT had a bit of a bounce idling at red lights. Don't get me wrong, I love the old big block muscle cars with carburetors that ran like that but seemed odd that a basically stock injected 302 would have any of that.

Tonight after work I went and changed the PCV and cleaned that screen assembly that is under it. Then I changed the cap and rotor. I didn't think this would really change the way it ran at all, I was just trying to get to all the routine maintenance items done because the car has sat for so long and I have no idea when (if ever) they were done.

To my surprise, when I fired the car up and did the test drive, that bounce is almost all gone and it is noticeably smoother.

The PCV valve appeared to be original but the piece inside was still moving freely, and the screen piece was dirty but really didn't look that bad. The cap and rotor I took off had some build up on the terminals but again, didn't look that bad. I was just really surprised that the two made such a difference.
 

mikestang63

SN Certified Technician
Aug 27, 2012
11,606
8,859
214
In the garage
Apr 28, 2017
#2
  • Apr 28, 2017
  • #2
like any other stock motor, it should run smooth
 

5.0specialist

Active Member
Jul 10, 2016
141
53
48
venice fl
Apr 28, 2017
#3
  • Apr 28, 2017
  • #3
2007_Crown_Vic said:
Hi Guys,

Should a stock foxbody run fairly smooth? My 1990 GT had a bit of a bounce idling at red lights. Don't get me wrong, I love the old big block muscle cars with carburetors that ran like that but seemed odd that a basically stock injected 302 would have any of that.

Tonight after work I went and changed the PCV and cleaned that screen assembly that is under it. Then I changed the cap and rotor. I didn't think this would really change the way it ran at all, I was just trying to get to all the routine maintenance items done because the car has sat for so long and I have no idea when (if ever) they were done.

To my surprise, when I fired the car up and did the test drive, that bounce is almost all gone and it is noticeably smoother.

The PCV valve appeared to be original but the piece inside was still moving freely, and the screen piece was dirty but really didn't look that bad. The cap and rotor I took off had some build up on the terminals but again, didn't look that bad. I was just really surprised that the two made such a difference.
Click to expand...

Replace the spark plugs with motorcraft ASF42C copper plugs, and if the ignition coil looks old, replace it. Mine began idling on the choppy side and I replaced with a motorcraft replacement coil. Not only did the idle smooth out completely, but the car felt more alive. There was a definite increase in power. I think the coil was the original 91' coil. lol
 

2007_Crown_Vic

Active Member
Aug 19, 2016
133
26
48
Apr 29, 2017
#4
  • Apr 29, 2017
  • #4
Good to know. The coil and plugs were already on my list anyway. Next time I place a Rockauto order I will add those. Or maybe see if LMR has them. I want to do the subframe connectors too and Rockauto doesn't have them.

It is really nice to get a car in as good of shape as this one due to it sitting for so long, but it seems what you get in the body being in great shape and low mileage, you pay for in the things like suspension and routine maintenance that has gone over looked for so long.
 
Reactions: 5.0specialist
S

sal5.0

Member
Jul 14, 2007
40
12
18
Apr 30, 2017
#5
  • Apr 30, 2017
  • #5
In my opinion... Nothing compares to stock/factory as far as driveabilty, and being reliable. It should run very smooth as long as everything is operating the way it should the day it rolled out of the assembly line.
 
S

stpete

Well-Known Member
Dec 26, 2015
320
151
63
Apr 30, 2017
#6
  • Apr 30, 2017
  • #6
There's a bunch of common things that cause a rough idle. Google "Mustang Surging Idle Checklist" and follow that. My car took a lot of effort as just about every step helped. I eventually got it idling perfectly cold and hot. You started off right, I think the checklist assumes you started by doing a basic tune up.
 

General karthief

wonder how much it would cost to ship you a pair
5 Year Member
Aug 25, 2016
27,872
10,542
203
polk county florida
Apr 30, 2017
#7
  • Apr 30, 2017
  • #7
No where here have I seen that you looked for codes, codes can be present without the check engine light on.
https://www.stangnet.com/mustang-fo...codes-from-eec4-in-86-95-5-0-mustangs.889006/
This will tell you how to pull codes, another link is the surging idle check list, a lot of people contributed to these help threads and they work, just follow the directions and you'll be running smooth again.
http://forums.stangnet.com/showthread.php?t=698148
 
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