• Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech

What would cause one side of my engine to be lean?

  • Thread starter Thread starter BlackFox5.0
  • Start date Start date May 19, 2004

BlackFox5.0

Founding Member
Aug 7, 2000
3,514
1
0
Massachusetts
May 19, 2004
#1
  • May 19, 2004
  • #1
I have been having a bucking (miss) problem lately. I took out all my plugs and looked at them and the passenger side of the engine had white ground straps on the plugs, the dirvers side were just normal looking, the tanish brown color.

I did pull the upper off to change my FPR, and I lifted the rail torwards the back of the engine (closer to the firewall) and that one injector came out of the intake I think.

Could I have a clogged injector or something? I can't figure it out
 

blown93feature

New Member
Dec 9, 2003
151
0
0
living on edge like the motor
May 19, 2004
#2
  • May 19, 2004
  • #2
I don't understand why the pass side is lean looking it's usually the driver side cylinder 7&8 and number five is usualy the one that gets left out of everything.I see that you have a "A" with a 306 and 36"s very nice.I didn't see you mention fuel pressure on wot do you know what it is?

I have 30"s with an s and factory fuel system except for the 2 255 pumps and I run the ffpr and have no chip or fmu at the time of dyno last week and If you want to see lean how about 14.7/1 can you say omg...I have put the fmu back on and were going back tomorrow and shooting for 500.Just for reference all my plugs were grey at the time of dyno and the best way to check plugs is right after you run the car at wot this way the motor dosen't have a chance to change the appearence of them.

edit" I forgot to ask what gap are you running and temp rated plug.I would check your plug wires to see if one is loose or arking.I run my gap around 38 to 40 thousands and use autolite 3923 plugs perfect set up..
 

BlackFox5.0

Founding Member
Aug 7, 2000
3,514
1
0
Massachusetts
May 19, 2004
#3
  • May 19, 2004
  • #3
I have a stock regulator right now, I'm putting my adjustable one back on as we speak, I also sprayed out the screens in all the injectors, and swapped the drivers side over to the passenger.

I have Autolite 23's for plugs gapped at .035"

Plug wires are fine, just checked them. All plugs are firing.

I also have a high pressure Walbro (holley) 255lph pump
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,260
17,944
224
Massachusetts
May 19, 2004
#4
  • May 19, 2004
  • #4
O2's?

Didn't you say 1 was original? They tend to fall out of calibration after so long
 

BlackFox5.0

Founding Member
Aug 7, 2000
3,514
1
0
Massachusetts
May 19, 2004
#5
  • May 19, 2004
  • #5
Yeah but I checked the output voltages, and they were ok. I am going to tune my FP and see how it turns out, when I just started it cold, it didn't stutter like it usually does, so maybe I fixed it...I'll post back...
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,260
17,944
224
Massachusetts
May 19, 2004
#6
  • May 19, 2004
  • #6
The output voltages may be good, but it could be reading lean as good if ya know what i mean. That's why i said the calibration tends to go off. It might think it's reading ok when it's not
 

BlackFox5.0

Founding Member
Aug 7, 2000
3,514
1
0
Massachusetts
May 19, 2004
#7
  • May 19, 2004
  • #7
Well it drives a little bit better, it seems to buck when I go down hill with my foot still on the pedal and not giving it any more gas. I set my FP to around 53psi.

I think i should change the O2's soon too....
 

Mustang5L5

That is…until I whipped out my Bissell
Mod Dude
Feb 18, 2001
43,260
17,944
224
Massachusetts
May 19, 2004
#8
  • May 19, 2004
  • #8
Just give me your supercharger. I think it will be happy on my car. I'll trade you my 02's in return!
 

BlackFox5.0

Founding Member
Aug 7, 2000
3,514
1
0
Massachusetts
May 19, 2004
#9
  • May 19, 2004
  • #9
You don't want it, it makes more problems. I didn't expect to spend so much more money after I got it
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
34
129
May 19, 2004
#10
  • May 19, 2004
  • #10
Chris, im with Mike on this one too. the Fuel pressure is a reflection of the primary delivery - if you have too little pressure, both banks are affected the same (more or less). since you are lean on one bank, i would look for things that are bank specific....like the lambda on that side.
someone in here has a thread where they say that they get O2's for 30 bucks each...im waiting for them to reply to see where they got them for that price (and it better not be 30 bucks plus 10-15 for shipping!).....i will post that info on your thread if it ever is revealed....

good luck.
 

BlackFox5.0

Founding Member
Aug 7, 2000
3,514
1
0
Massachusetts
May 20, 2004
#11
  • May 20, 2004
  • #11
Thanks. It did get better for sure, but I can feel it mostly in 5th gear and cruising around 2000-2500rpm I'll have to see what the plugs are like now.

I've gotta fix this before saturday!!!!!!!!!
 

blown93feature

New Member
Dec 9, 2003
151
0
0
living on edge like the motor
May 20, 2004
#12
  • May 20, 2004
  • #12
HISSIN50 said:
Chris, im with Mike on this one too. the Fuel pressure is a reflection of the primary delivery - if you have too little pressure, both banks are affected the same (more or less). since you are lean on one bank, i would look for things that are bank specific....like the lambda on that side.
someone in here has a thread where they say that they get O2's for 30 bucks each...im waiting for them to reply to see where they got them for that price (and it better not be 30 bucks plus 10-15 for shipping!).....i will post that info on your thread if it ever is revealed....

good luck.
Click to expand...


I get my 02's for 36 bucks @autozone can't beat it!!!
 
B

blk9450

Founding Member
Jan 31, 2002
1,507
0
0
your moms bed
May 21, 2004
#13
  • May 21, 2004
  • #13
i was amazed the other day when i bought o2s at autozone. i remember at the other place by me like 2 years ago the things were like $80 each. bosch units too autozone=
 

HISSIN50

"How long does it take to get help in here?
15 Year Member
Nov 29, 1999
31,179
34
129
May 21, 2004
#14
  • May 21, 2004
  • #14
Blown, thanks for the info. i should do them, if i ever get off my butt.
thanks again!
 

BlackFox5.0

Founding Member
Aug 7, 2000
3,514
1
0
Massachusetts
May 21, 2004
#15
  • May 21, 2004
  • #15
Ok, I unplugged my O2s, and the car is bucking more than withthem plugged in....what does that say?

My friend just did O2s on his car and gave me the ones he took out to test on mine, He said one sensor is like 6 months old. If it's nice out today I am going to put them in and see what happens
 

astronut1885

Founding Member
Jan 31, 2002
1,899
4
39
Assonet, MA
May 21, 2004
#16
  • May 21, 2004
  • #16
I got new Denso O2s for 45.00 a piece at a local store, and they helped calm my idle alot. Hopefully my fuel mileage will go up with working O2s in the system. Good luck with my old ones chris.
 
You must log in or register to reply here.

Similar threads

T
Fuel Looking for a little guidance
  • Tufgriz
  • Sep 11, 2025
  • Fox 5.0 Mustang Tech
Replies
9
Views
363
Fox 5.0 Mustang Tech Sep 12, 2025
Noobz347
T
  • Locked
Digital Tuning A9l issue or something else
  • Tufgriz
  • Sep 11, 2025
  • Fox 5.0 Mustang Tech
Replies
2
Views
290
Fox 5.0 Mustang Tech Sep 11, 2025
Noobz347
9
Engine Donor '00 Mountaineer meet '91 Fox
  • 91firecracker
  • May 11, 2026
  • Fox 5.0 Mustang Tech
  • 2 3
Replies
41
Views
917
Fox 5.0 Mustang Tech May 28, 2026
91firecracker
9
Electrical 88 EEC Injectors batch firing ?
  • Dustin 86GT
  • Dec 8, 2025
  • Fox 5.0 Mustang Tech
Replies
10
Views
440
Fox 5.0 Mustang Tech Jan 8, 2026
gkomo
L
95 gt engine vibration
  • lenzgt
  • May 11, 2026
  • 1994 - 1995 Specific Tech
Replies
6
Views
216
1994 - 1995 Specific Tech May 26, 2026
lenzgt
L
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • Fox 5.0 Mustang Tech
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?