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  • SN95 4.6L Mustang Tech

is my fuel pressure right?

  • Thread starter Thread starter Brute03
  • Start date Start date Dec 2, 2007

Brute03

Member
Mar 20, 2006
232
0
16
Dec 2, 2007
#1
  • Dec 2, 2007
  • #1
hey guys, i'm trying to track down an on-going problem i'm having. my car idles rough, hesitates, gets poor economy and is down on power.

i checked the fuel pressure and i'm getting 26-28psi @ idle and around 38psi with the vacuum line off, are those numbers considered to be normal?
 

DBMSTNG

I fantasize about it being BIG!
Founding Member
Apr 23, 2002
2,120
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56
not quite here
Dec 2, 2007
#2
  • Dec 2, 2007
  • #2
sounds a little high for a stock setup to me, but not by alot.
 

Brute03

Member
Mar 20, 2006
232
0
16
Dec 2, 2007
#3
  • Dec 2, 2007
  • #3
high? i though it seemed a little low.
 

blkhorse

Founding Member
Oct 30, 1999
345
1
18
Dec 2, 2007
#4
  • Dec 2, 2007
  • #4
should be about 39 psi at 0" manifold pressure and 29lbs at 20" vacuum,so he's real close
 

Mike97gt

it doe snot
Founding Member
Jan 26, 1999
10,633
7
89
the people's republic of massachusetts
Dec 3, 2007
#5
  • Dec 3, 2007
  • #5
IF it drops while you are floored or under heavy load by a lot then I would look at the pump..

BUT since it seems ok

I bet you have a plug or coil concern, 99 percent of the time when these cars run rough and have the symptoms you have it's a secondary ignition concern..

Drive up a steep hill at low rpm's in 3rd or 4th gear and if this thing bucks and shudders then you have a misfire under load. If it's idling rough you might be able to tell what plug is not firing by pulling thme out and looking for the fuel fouled one.
 
F

ForPointSex

Founding Member
Mar 19, 2002
395
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16
Mercer, NJ
Dec 3, 2007
#6
  • Dec 3, 2007
  • #6
My car gets 40PSI. When my fuel pump was bad, it dropped down to 10PSI over 3500RPM. When the car was still, it showed no signs of being bad since the engine was not using enough gas for a pressure drop.


If you can, watch your fuel pressure while your driving and see if it drops.


I've also had a bad coil pack. It would miss under any load. It was fine on idle. I ordered a new one from ebay for $30 and swapped it 1 by 1 until I found a bad one.
 

Brute03

Member
Mar 20, 2006
232
0
16
Dec 3, 2007
#7
  • Dec 3, 2007
  • #7
well i bought all new accel replacements hoping that it would fix the problem but no such luck, so that's why i think the problem might be on the fuel side
 
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