4.3 liter vortec, need help with strange issue. - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- 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
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 11-13-2012, 08:52 PM
Registered User
 
Last photo:
Join Date: Jan 2010
Location: Vancouver, B.C.
Posts: 141
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
4.3 liter vortec, need help with strange issue.

Hey guys. Truck is a 1994 Chevy S10 SS 4.3 vortec. Engine has developed a strange condition where it will surge every now and then, even while cruising at highway speed with foot off the throttle. It happened while my friend was driving it and she almost rammed into the car ahead of her as the truck just took off on its own, even while she was standing on the brake pedal, as if the throttle and pedal are being depressed at the same time! Did some preliminary checks and Ive found nothing obvious...... No check engine light, no misfire (I think) etc. Without a check engine light on this is very hard to diagnose, Im thinking a sensor is on its way out and signaling for fuel when its not needed? Possibly an O2 sensor sensing a false lean condition and signaling for more fuel? Anyone had similar pblems with these engines?

Thanks,
Keith

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 11-13-2012, 09:15 PM
31 five window
 

Last journal entry: Master cylinder
Last photo:
Join Date: Oct 2007
Location: louisiana
Age: 57
Posts: 1,577
Wiki Edits: 0

Thanks: 1
Thanked 14 Times in 14 Posts
I am far from an expert on these newer vehicles but I have a 94 GMC Sonoma with the 4.3. It might be the throttle position sensor.Hope this helps.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 11-13-2012, 09:30 PM
Registered User
 
Last photo:
Join Date: Jan 2010
Location: Vancouver, B.C.
Posts: 141
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Hey thanks for the suggestion, never thought of that and it would make sense. Just strange that there is no check engine light on thus no codes for any failed sensors. Will have to lool into that though
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 11-13-2012, 10:19 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 13,097
Wiki Edits: 326

Thanks: 781
Thanked 1,063 Times in 882 Posts
Toyota had the same problem a few years back when I sold Toyotas, happened to me on a test drive with a customer. Check with the local dealer, see if there has been a recall.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 11-14-2012, 05:02 AM
Registered User
 
Join Date: Jun 2010
Location: TX
Posts: 1,218
Wiki Edits: 0

Thanks: 0
Thanked 108 Times in 99 Posts
There is not much room between the accelerator and the brake pedal on S10 vehicles. If the brake pedal gets too low and if you foot is not positioned correctly on the brake when it is applied, you can accidentally depress the accelerator and the brake at the same time. That has happened to me a few times and it is scary. Bleed ABS brakes of any residual air to prevent the pedal from sinking to the level of the accelerator pedal. There were recalls in the 1990s about such incidents and I am sure some were related to the ABS brakes having air in the system.

When I drive my S10, I often wear Simpson high-top racing shoes that have narrow soles. The soles on those racing shoes were designed years ago to be used in front engine dragsters that have a small foot box. You should never wear work boots or wing tips while driving an S10. .
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 11-14-2012, 06:11 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 60
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by 383SBC View Post
Hey guys. Truck is a 1994 Chevy S10 SS 4.3 vortec. Engine has developed a strange condition where it will surge every now and then, even while cruising at highway speed with foot off the throttle. It happened while my friend was driving it and she almost rammed into the car ahead of her as the truck just took off on its own, even while she was standing on the brake pedal, as if the throttle and pedal are being depressed at the same time! Did some preliminary checks and Ive found nothing obvious...... No check engine light, no misfire (I think) etc. Without a check engine light on this is very hard to diagnose, Im thinking a sensor is on its way out and signaling for fuel when its not needed? Possibly an O2 sensor sensing a false lean condition and signaling for more fuel? Anyone had similar pblems with these engines?

Thanks,
Keith
I have no ideas per se- but still check for codes, even w/no CEL lit.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 11-14-2012, 07:08 AM
gearheadslife's Avatar
MentalMuffinMan
 
Last photo:
Join Date: Nov 2012
Posts: 2,328
Wiki Edits: 0

Thanks: 130
Thanked 310 Times in 288 Posts
do the 4.3 vortec have the spiders that leak and cause this on the v8's

just a thought..
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 11-14-2012, 08:11 AM
Registered User
 
Last photo:
Join Date: Jun 2010
Location: Syracuse, NY
Posts: 2,291
Wiki Edits: 0

Thanks: 606
Thanked 236 Times in 211 Posts
This is very unorthodox, but it happened to me; in a 96 S10. I had the cruise control activated and was resting my left foot lightly on the brake pedal; my right foot was on the floor in front of the accelerator. I stepped on the brake for an upcoming exit and the truck surged. My right foot had accidentally lodged the floormat under the accelerator pedal
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 11-14-2012, 08:41 AM
1Gary's Avatar
Registered User
 

Last journal entry: 383 dyno sym
Last photo:
Join Date: Oct 2010
Location: Roch,NY
Age: 67
Posts: 1,538
Wiki Edits: 0

Thanks: 201
Thanked 156 Times in 142 Posts
1994/1995 was a transitional yrs for 4.3's.In 1994 it could be either a TBI or with the W engine a CPI that does have spiders that might leak.A fuel pressure check is going to help to better understand one part of this.Also check engine lights doesn't happen often with a clogged Cat.If the problem goes away by removing the 02 before the cat and running it open,then it is likely a clog Cat.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

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:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

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
Strange Voltmeter Issue Leoman Electrical 7 02-27-2013 01:11 PM
strange overheating issue... 19deuce71 Engine 8 09-21-2010 06:00 AM
very strange issue Geddy Engine 1 09-09-2009 10:08 PM
Really strange 200R4 issue, Night Wolf Transmission - Rearend 13 07-30-2007 03:43 PM
Very strange brake issue. Help! 68NovaSS Suspension - Brakes - Steering 5 03-21-2006 12:06 AM


All times are GMT -6. The time now is 01:44 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.