Go Back   LS1TECH > SBC-BBC-LT1-LT4 PERFORMANCE > LT1-LT4 Modifications
Sign in using an external account
Register Forgot Password?
Register iTraderTimeslips Photos Members Search Today's Posts Mark Forums Read Used CarsVendor Directory
Search

LT1-LT4 Modifications
1993-97 Gen II Small Block V8

Welcome to LS1Tech.com!
Welcome to LS1Tech.com.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join LS1Tech.com today!


Reply
 
Thread Tools Search this Thread
Old 11-13-2010, 09:22 AM   #1
Teching In
Garage is empty, add now
 
Trader Rating: 0
Join Date: Oct 2005
Location: New Jersey
Posts: 28
Send a message via AIM to chupacabra Send a message via MSN to chupacabra
Default FIXED / HOW TO: IAC, engine dies when stopping, rough idle, TB bypass

Hello all, well my recently acquired LT1 bird just had it's first bug for me to iron out. I haven't picked up a wrench on any of my cars in over 2 years, so I was excited to have a chance to work on the car. I'm gonna post this so if other people have the same or similar problems, hopefully this will pop up in the search for them. I wasn't planning on doing a write up so the pictures are kind of scattered, but you'll get the point.

THE PROBLEM: Car had a super rough idle (no cam) and the engine slowly died when coming to a stop, or making 3 point or slow speed turns.

POSSIBLE CULPRITS: Idle Air Control Valve (IAC) or Vaccum Leak. I tackled the #1 suspect first, the IAC.

PROCESS OF FIXING: First thing's first, gotta remove the air intake system. My car being Ram Air was fairly easy, as a bonus I got to install my new K&N filter. Once your intake and mass air system are out of the way, it's time to un-plug all the tubes off the throttle body.

In order from top to bottom on the passenger side you have:
top- PCV tube (some oil might drip out of this one)
middle- vaccum hose that goes back towards the EVAP solenoid
bottom- stubby coolant line ran to the metal pipe runnig from the back of the passenger head.

On the driver side of the throttle body you have:
top- throttle linkage, to remove, just pull the cable to WOT (wide open throttle) and unhook the throttle and cruise cables.
Underneath that theres another coolant hose.


*** MAKE SURE YOU HAVE PLENTY OF TOWELS STUFFED UNDER THE TB AND ALL AROUND THE OPTI BEFORE YOU REMOVE THE COOLANT HOSES. COOLANT CAN AND WILL SPILL OUT AND RUIN THE OPTISPARK! ***
Click the image to open in full size.

Once all your hoses and wires are disconnected, unscrew the throttle body x4 10mm bolts. You should now have a throttle body in your hand.
Click the image to open in full size.

The IAC valve is sticking out of the bottom left side of the TB and held on by 2 torx bolts, unscrew them and it should slide right out. DO NOT MOVE THE PLUNGER IN/OUT OR TRY TO ROTATE IT, YOU WILL RUIN THE VALVE. Soaked the spring and plunger in wd40 for about 10 minutes, hit it with some carb cleaner, 5 QTips and compressed air, 125k miles of crud GONE.
Click the image to open in full size.

Take some time to spray down the throttle body and clean that out too, be careful not to soak the TPS sensor, Carb cleaner can ruin electrical connections. Used some more QTIPS to get inside the IAC housing.

I opted to do the THROTTLE BODY COOLANT BYPASS at this time, since everything was apart. Very simple, remove the stubby coolant pipe from the pipe going to the back of the head. I removed the alternator bracket for easier access, 14mm attached to the intake and 2 13mm on the alternator side. Once that tube is removed, take the tube that was originally running to the driver side of the throttle body and plug it into that metal tube. This is the long tube coming from the coolant overflow by the radiator cap. Finished witht the bypass and it looks stock too, so I was happy with that.
Click the image to open in full size.
Click the image to open in full size.

Put everything back together in reverse order and it's almost finished. YOU HAVE TO RESET THE IAC. Press in the clutch (if it's a 6 speed) and press the accelerator to the floor, crank the engine for 10 seconds, turn ignition to OFF position, wait 5 seconds then start the car. DONE.

I hope this helps anybody who's car was suffering the same symptoms as mine.

-Terry
__________________
TERRY - 1996 WS6 Trans Am T-Top M6
chupacabra is offline   Reply With Quote
Old 11-17-2010, 10:59 PM   #2
Staging Lane
Garage is empty, add now
 
Trader Rating: 5
Join Date: Sep 2010
Location: Kansas
Posts: 89
Default

i replaced mine & am still having the problem
__________________
99 Firehawk #210
Restored 68 SS350
-
03 Mercedes AMG E55 Kompressor
07 Infiniti G35X
carguyshu is offline   Reply With Quote
Old 12-02-2010, 03:04 PM   #3
Teching In
Garage is empty, add now
 
Trader Rating: 0
Join Date: Oct 2005
Location: New Jersey
Posts: 28
Send a message via AIM to chupacabra Send a message via MSN to chupacabra
Default

Quote:
Originally Posted by carguyshu View Post
i replaced mine & am still having the problem
your car was doing the same thing? did you reset it after installing the new one?
__________________
TERRY - 1996 WS6 Trans Am T-Top M6
chupacabra is offline   Reply With Quote
Old 12-02-2010, 03:35 PM   #4
TECH Apprentice
Garage is empty, add now
 
Trader Rating: 5
Join Date: May 2010
Location: Central Valley, CA
Posts: 365
Default

what year is your car? lol i seriously thought that the IAC was the black unit on top of the intake manifold right behind the throttle body plate in the first picture, where the green male pigtail plugs in, i guess im wrong lol...does anyone know what that is?
__________________
98' SS - LQ9, Turbo Cam, LS6 intake, Edelbrock Longtubes, E-Cutout, 400whp
05' ZX-10 - Stock
LT1559 is offline   Reply With Quote
Old 12-02-2010, 03:39 PM   #5
Staging Lane
Garage is empty, add now
 
Trader Rating: 5
Join Date: Sep 2010
Location: Kansas
Posts: 89
Default

it only has the problem when cold & it tries to idle at like 150 rpm & will surge and die. I had the car in storage for 3 years and got it back out this summer. If having a disconnected battery for 3 years doesnt reset it then I'm not sure what would
__________________
99 Firehawk #210
Restored 68 SS350
-
03 Mercedes AMG E55 Kompressor
07 Infiniti G35X
carguyshu is offline   Reply With Quote
Old 12-02-2010, 03:41 PM   #6
On The Tree
Garage is empty, add now
 
Trader Rating: 3
Join Date: Jul 2009
Location: michigan
Posts: 127
Default

LT1 ,that is called the map sensor..
__________________
"The Money Pit"
my1994z28 is offline   Reply With Quote
Old 12-02-2010, 03:41 PM
LS1Tech
Pontiac Firebird




Paid Advertisement
Reply

Tags
93, air, car, control, dies, engine, iac, idle, install, intake, lt1, reset, rough, stopping, turns, valve, z28


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 On
Refbacks are Off



All times are GMT -5. The time now is 05:35 AM.


Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.5.2
Advertising - Terms of Service - Privacy Statement - JOBS
Emails & Contact Details