low rough idle - MustangForums.com

Go Back   MustangForums.com > Ford Mustang Tech > 5.0L (1979-1995) Mustang
Sign in using an external account
Register Forgot Password?

5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

low rough idle

Thread Tools Search this Thread
Old 07-20-2006, 03:03 AM   #1
Join Date: Dec 2004
Posts: 4
Default low rough idle

Hi everyone this is my first post. I didn't find any threads that helped me with my problem. hope someone here might have some insight.
The other day i went to start my car and the fuel pump was dead(over 160K on the stocker) so i ordered a 155 LPH from SUMMIT. I bought their SUMMIT pump(made by walbro) and installed it. my car starts faster and has smoother acceleration but i now have a very low stumbling idle. nothing else was done to the car at the time. For along time i've had an idle issue running A/C at an idle to the point of dying and figure the IAC is the culprit, but i've never had an unloaded idle problem. Could it possibly be a pressure problem and i need an adjustable regulator? OK thats all i can think of right now. Thanks for any help.
'95 GT,AODE,transgo,KN,cold air int.,flowmaster.

95DkGrnGt is offline   Reply With Quote
Old 07-20-2006, 03:43 AM   #2
5th Gear Member
Join Date: Feb 2006
Posts: 2,524
Send a message via AIM to FiveLiterRiceEater
Default RE: low rough idle

pressure is probably fine. it sounds like you might have a dirty or plugged up iac passage. pop it off and clean it out real good. you can also do a koeo test and see if you get any codes.
FiveLiterRiceEater is offline   Reply With Quote
Old 07-20-2006, 03:51 AM   #3
5th Gear Member
Join Date: Mar 2006
Vehicle: 1989, Mustang GT
Location: Massachusetts, New Bedford
Posts: 3,035
Default RE: low rough idle

ORIGINAL: FiveLiterRiceEater
i like ur name btw.

1989 GT Bright Regatta Blue and Titanium
SVO GT40x Aluminum Heads, FRPP F303 Cam, Trick Flow Track Heat Intake w/ 3/8" spacer, 3.73s, Full Exhaust and Suspension

13.024 @ 105.8mph w/ 1.914 60' getting closer to 12s..

This Car is For Sale
nacanitihs is offline   Reply With Quote
Old 07-20-2006, 09:41 AM   #4
3rd Gear Member
Join Date: May 2006
Location: Kannapolis NC
Posts: 544
Default RE: low rough idle

I had a really rough idle, it was because the pump wasn't giving the engine enough gas.
If you still have the time or still up to it, try moving up to a 190lph or 255lph...it depends on everything you have on the engine.
RacquetballRyan is offline   Reply With Quote
Old 07-20-2006, 01:14 PM   #5
5th Gear Member
Join Date: Mar 2006
Location: Greenville SC
Posts: 2,317
Default RE: low rough idle

My 255 bumbed out and i just stuck a stocker in because its all i got till i get paid, im very curious about how much this is actually hurting my performance. It definatly is dragging *** on the top end now, only ran it up to there once, i worried about running lean at those higher rpms. I was watching my fuel pressure as i accelerated and it went from the 40's to near 10psi before i finally let off.

I also think its your IAC, as fiveliterriceeater said, get some carb and choke cleaner and spray it all in there and let it sit for a few min's. Then get scrub it really nice. Even get some compressed air and blow it out really nice.
1988 Notch. 306, 150NO2, AFR 185's, F-cam. 11.68@124mph.
1985 LX hatch. 69' 302 block, stock internals, MPT70, Megasquirt II, 42# injectors, C4 w/reverse manual/brake. Its a project in process......looking for mid-10's though.

88stangaruu is offline   Reply With Quote
Old 07-21-2006, 02:16 AM   #6
Join Date: Dec 2004
Posts: 4
Default RE: low rough idle

Thanks for the fast responses. I took off the IAC and cleaned it out with brake clean, it was all i had here, and it seems to be OK now. I have an idle of about 600-650 RPM and no surge with the A/C either.
'95 GT,AODE,transgo,KN,cold air int.,flowmaster.

95DkGrnGt is offline   Reply With Quote


50, 69, 95, ac, aod, fox, gt, idle, low, mustang, rough, start, startup, stumbling, supercharger

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
californiaspec kevans79@yahoo.com General Tech 0 08-18-2015 08:16 AM
Rough Idle Issue HELP!!!!!!!!!! fdnyems19 5.0L (1979-1995) Mustang 2 08-13-2015 09:36 AM
Need Help Diagnosing Have Codes (Confused) djbigskrilla 2005 - 2014 Mustangs 13 08-11-2015 12:59 PM
Rough idle bluovalguy 5.0L (1979-1995) Mustang 5 08-04-2015 09:26 AM
97 GT High idle/ no power belcher0213 4.6L (1996-2004 Modular) Mustang 1 08-02-2015 05:26 PM

Featured Sponsors
Vendor Directory
New Sponsors
All times are GMT -5. The time now is 03:10 AM.>

© Internet Brands, Inc.

This forum is owned and operated by Internet Brands, Inc., a Delaware corporation. It is not authorized or endorsed by the Ford Motor Company and is not affiliated with the Ford Motor Company or its related companies in any way. Ford® is a registered trademark of the Ford Motor Company
Emails Backup