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

1990 Msutang GT will not idle on its own and struggles to get even 25mph

  • Thread starter Thread starter DSGB347
  • Start date Start date May 29, 2009

DSGB347

New Member
Mar 7, 2009
14
0
0
45
Fort Walton Beach
May 29, 2009
#1
  • May 29, 2009
  • #1
I am having trouble getting my car drivable. I resently bought it with a super charger with 6lbs boost I believe. It will not idle on its own checked everywhere for vacuum leaks; found none. even temp duct taped around the couplings to make sure the where sealed good. I am not sure if the pipe that would usually dump smog/unspent fuel into the exhaust matters but the exhaust is after maket and there is no smog tube one it but i pluged the smog tube anyhow still no idle. I installed a Kirban adjustable regulator and no matter where it is set doesn't help. It does seem to smell rich if I turn it up high. I have a FMU I'm running the also. Right now I can only get the car running when its warm after a few tries of starting and feathering the gas. I've tried a new TPS the IAC is new EGR and EGR valve is new I tried to adjust the TPS voltage but it doesn't matter where it is it still won't idle. and turning the idle screw to far just makes the fast idle sore way too high only to drop off and not idle correctly. If I trie to drive I can only get to 25mph and that comes with poping in the exhase not matter where I adust the timing. It has a Walbro 255 lph fuel pump must recently today I got a code 87 and 95 I'm goin to change the fuel pump relay tomarrow but I don't think thats the problem. I just don't know what to do. Should I try to gut the smog stuf to make its simpler. It still has a smog pump. I am stopped I know this car has run set up the way it is before. I'm also using autolite 24s gapped and 35degress I don't think I'm getting spark blow out? 92octane gas, boost controller. What else should I do? I'm starting to miss my 347 stroker car.
 
9

90bluegt

Founding Member
Dec 9, 1999
592
0
16
Jun 3, 2009
#2
  • Jun 3, 2009
  • #2
You need to get it tuned.. Just my opinion, but go get a moates Quarterhorse (Welcome to www.moates.net! : Moates.Net) and Clints BE/EA (EEC Analyzer) and tune that car. Also, hit the site EECTuning.org • Index page and you'll see what I mean.

People will probably dis-agree with me, but after everything that I tried with my car to get it to run. I bought a tweecer first (got it running well) then sold that and got the moates QH and tuned it. Thing runs like stock now, just with a lot more horse.
 
S

stangbang302

New Member
Jul 13, 2007
180
0
0
fort valley, ga
Jun 21, 2009
#3
  • Jun 21, 2009
  • #3
my car used to do that it hesitated to rev and wouldnt go fast at all, found out that my problem was clogged fuel injectors
 

86turbo

Member
Apr 8, 2006
183
0
17
Sep 24, 2009
#4
  • Sep 24, 2009
  • #4
sounds like fuel to me. I would take the blower off and try and get the car running right. Wouldn't be the first time i've heard of someone putting a sc on an engine that isn't running well anyway..

just a thought

Drew
 

ddonaca351

Active Member
Dec 1, 2002
2,055
1
48
56
Camas Washington
Sep 24, 2009
#5
  • Sep 24, 2009
  • #5
(imho)
Set the distributor to 10-12 degrees, no more.
Set the fuel pressure regulator to 38-40 psi at idle
Set the idle adj screw to 1 turn past first touch
Set TPS voltage to .95vdc or less DO NOT go over 1v
Make sure the MAF is the correct cal for the size of injectors that are in the car.
Check the daiphram in the FMU to make sure it's correct for the injectors and boost level of the car. (blower manuf. web site / tech line should be able to help)

If none of that helps, you could try a local tuner or remove the blower kit, but try the simple stuff first.
 
You must log in or register to reply here.

Similar threads

S
Fuel ‘88 GT Runs Rich Cold — Fixes Itself When I Unplug Sensors (ECT, MAF, O2, etc.)
  • Sufarry
  • Nov 6, 2025
  • Fox 5.0 Mustang Tech
Replies
12
Views
884
Fox 5.0 Mustang Tech Nov 9, 2025
Mustang5L5
Engine 1990 LX 5.0L EFI Mustang Fuel Management Problems - HELP!
  • 5.0LXStanger
  • May 25, 2025
  • Fox 5.0 Mustang Tech
  • 2 3
Replies
45
Views
2K
Fox 5.0 Mustang Tech Jul 11, 2025
5.0LXStanger
8
Engine Rough idle and aggressive sputtering when accelerating
  • 88vertible
  • Aug 13, 2025
  • Fox 5.0 Mustang Tech
Replies
4
Views
1K
Fox 5.0 Mustang Tech Dec 13, 2025
Jarhead67
J
S
Fox '87 GT can't get to stay running
  • spilly
  • Mar 29, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
  • 2
Replies
27
Views
845
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 20, 2026
spilly
S
L
95 gt engine vibration
  • lenzgt
  • May 11, 2026
  • 1994 - 1995 Specific Tech
Replies
6
Views
224
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?