inconsistent idle/ motor surge - Hot Rod Forum : Hotrodders Bulletin Board -- Hot Rod Forum

Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 12-12-2010, 09:18 AM
Registered User
Join Date: Dec 2010
Location: allen
Posts: 1
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
inconsistent idle/ motor surge

i have a 1977 ford f100, 302 with an edelbrock performer intake and performer carb. Once motor has reached normal temperature, the rpms will not stay consistent and the motor begins surging from 1400rpm done to 700 or so. I've fixed a few vacuum leaks and pulled the carb, checked floats, jets, ect.. and things look ok. a little corrosion on the metering rods. one main concern is the right air/fuel mixture screw, is not working. Would this be causing the surging problem and or could something else be causing the problem?

Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 12-12-2010, 10:45 AM
DoubleVision's Avatar
Not Considered a Senior Member
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 43
Posts: 10,733
Wiki Edits: 0

Thanks: 19
Thanked 77 Times in 71 Posts
Usually when a idle mixture screw doesn`t work it means there`s excessive trash in the idle circuit so no fuel is flowing through it. That or the fuel pressure is too high forcing fuel out of the booster or the float level is too high or the timing is too low which means the butterflies are open too far resulting in it pulling fuel from the boosters instead of the idle circuit. But since it`s only one side I`m thinking the idle circuit is plugged. Why the idle goes up and down is because it`s not getting any fuel on that side so it`s forced to pull it from the main booster which is giving it far more fuel than the idle circuit ever would so the idle goes up from the excessive fuel. Yank the carb and rebuild it, clean out all the passages so you know they are working correctly. If you were using a open plane intake it wouldn`t be as obvious, as 1 runner pulls off the entire plenum of the carb. On the dual plane performer it`s divided so you have one side getting fuel and the other getting nothing.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 12-12-2010, 12:54 PM
eloc431962's Avatar
Evil Wicked Mean And Nasty
Last wiki edit: Pilot bearing and bushings
Last journal entry: roof repair
Last photo:
Join Date: Nov 2008
Location: back in the garage.
Posts: 13,766
Wiki Edits: 37

Thanks: 50
Thanked 31 Times in 26 Posts
X2 with DV,

Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Posting Rules
You may post new threads
You may 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 On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Idle Restrictors on 750DP Mighty Demon? My68Vette Engine 43 02-21-2012 08:09 PM
Carb tuning issues - 750 speed demon lightningcow Engine 48 07-01-2009 07:32 AM
Help tuning 383 for street use strokey Engine 29 04-11-2008 05:51 PM
DARK brown--BLACK plugs SBC Joshua Lee Engine 128 02-03-2008 09:12 AM
Vacuum adv.. underdog305 Engine 58 01-30-2007 11:19 AM

All times are GMT -6. The time now is 06:28 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.