98 gmc - Page 2 - Great Lakes 4x4. The largest offroad forum in the Midwest

Go Back   Great Lakes 4x4. The largest offroad forum in the Midwest > 4x4 Talk > Chevy Tech
GL4x4 Live! GL4x4 Casino

greatlakes4x4.com is the premier Great Lakes 4x4 Forum on the internet. Registered Users do not see the above ads.
Search
Reply
 
Thread Tools Search this Thread
Old August 21st, 2013, 03:11 PM   #21
wave_crusher
I'll Direc your TV
 
wave_crusher's Avatar
 
Join Date: 01-20-09
Location: Big Rapids, MI
Posts: 5,137
iTrader: (21)
Mentioned: 1 Post(s)
Default

Iac

You can use a multimeter to see if it is bad; I don't remember what you actually need to look for...just run to advance or autozone and look in one of their Haynes manuals.

The manual way that I know is to screw the end out all the way and start up your truck, it will probably die right away or idle very low. If the IAC is good then it should smooth out or at least go back to what is was before you screwed out the end of it. If the IAC doesn't move then it needs to be changed

I wouldn't think it's the TPS, in my experience a tps would just make the truck idle shitty, but once you're driving it would seem normal







....or maybe i am mixing up the two???? lol It's been awhile since I worked on a TB 350

Last edited by wave_crusher; August 21st, 2013 at 03:18 PM.
wave_crusher is online now   Reply With Quote
Sponsored Links
Advertisement
 
Old August 21st, 2013, 03:14 PM   #22
RivMan
Senior Member
 
Join Date: 04-18-10
Location: Belleville, Mi
Posts: 216
iTrader: (2)
Mentioned: 0 Post(s)
Default

Idle Air Control motor = the valve that opens and closes to adjust your idle speed.

High idle + a code for the IAC = BAD IAC.

Unplugging it just stops it from being controlled, if it's stuck open slightly, you'll see the exact behavior you describe.

-Rob
RivMan is offline   Reply With Quote
Old August 21st, 2013, 04:29 PM   #23
muddinman56
blood,sweat and beers
 
muddinman56's Avatar
 
Join Date: 10-06-08
Location: armada michigan
Posts: 3,691
iTrader: (18)
Mentioned: 0 Post(s)
Default

I unplugged the tps with no change.

The iac I unscrewed all the way put back in started the truck and pulled the iac off and it moved in close so I'm guessing that's not it?

And wave crusher I got ride of my 93 green chevy 350 tbi and now have a 98 red gmc vortec 350 lol
muddinman56 is offline   Reply With Quote
Old August 21st, 2013, 08:06 PM   #24
wave_crusher
I'll Direc your TV
 
wave_crusher's Avatar
 
Join Date: 01-20-09
Location: Big Rapids, MI
Posts: 5,137
iTrader: (21)
Mentioned: 1 Post(s)
Default

Quote:
Originally Posted by muddinman56 View Post
I unplugged the tps with no change.

The iac I unscrewed all the way put back in started the truck and pulled the iac off and it moved in close so I'm guessing that's not it?

And wave crusher I got ride of my 93 green chevy 350 tbi and now have a 98 red gmc vortec 350 lol
OHH maybe I should read then? lol 98 looks a lot like 93 right???

If you unplugged the tps and there was no change then I think you found your problem. Get a new one and make sure you don't scuff it when you put it in. If it doesn't work just take it back and say you got the wrong one. hence the not scuffing it part lol

It should be throwing a code though
wave_crusher is online now   Reply With Quote
Old August 21st, 2013, 10:29 PM   #25
muddinman56
blood,sweat and beers
 
muddinman56's Avatar
 
Join Date: 10-06-08
Location: armada michigan
Posts: 3,691
iTrader: (18)
Mentioned: 0 Post(s)
Default


My 98

I did get it scanned and auto zone but they can't tell what code is over lapping
The other it has a misfire but it does need a tune up badly but I know that's not causing the rpm problem.
They can't tell if the tps is overlapping the iac or the other way around.
But I'm not paying 60 bucks to get my truck live scanned just yet
muddinman56 is offline   Reply With Quote
Old August 22nd, 2013, 08:22 AM   #26
RivMan
Senior Member
 
Join Date: 04-18-10
Location: Belleville, Mi
Posts: 216
iTrader: (2)
Mentioned: 0 Post(s)
Default

An engine needs air to idle at 1300 rpm.

You have an air leak someplace, either a vacuum leak someplace, a dirty / leaking throttle plate, or a bad IAC.

-Rob
RivMan is offline   Reply With Quote
Old August 26th, 2013, 08:18 PM   #27
1994Dakota
No
 
1994Dakota's Avatar
 
Join Date: 08-17-10
Location: waterford
Posts: 39
iTrader: (0)
Mentioned: 0 Post(s)
Default

You might have a misfire and an idle problem because of a bad ignition control module. When those go bad they make the motor do some weird stuff

IIRC rock auto had them for like~40$
1994Dakota is offline   Reply With Quote
Old August 26th, 2013, 08:25 PM   #28
AJ Hall
Kickin' Up MUD
 
AJ Hall's Avatar
 
Join Date: 11-04-09
Location: USA
Posts: 1,988
iTrader: (5)
Mentioned: 16 Post(s)
Default

Spider injection is probably leaking. Very common. Also, the plastic is called the plenum and it bolts to the intake. Remove thay and you will see the spider injection. Thats the only bad thing with a vortec. Or simply the throttles sticking. I assume it idles high? Start it up and look at the throttle body..
AJ Hall is offline   Reply With Quote
Old August 26th, 2013, 08:28 PM   #29
AJ Hall
Kickin' Up MUD
 
AJ Hall's Avatar
 
Join Date: 11-04-09
Location: USA
Posts: 1,988
iTrader: (5)
Mentioned: 16 Post(s)
Default

Quote:
Originally Posted by muddinman56 View Post

My 98

I did get it scanned and auto zone but they can't tell what code is over lapping
The other it has a misfire but it does need a tune up badly but I know that's not causing the rpm problem.
They can't tell if the tps is overlapping the iac or the other way around.
But I'm not paying 60 bucks to get my truck live scanned just yet
Some autozones have a little bit bigger scanner. Like one step up from the little credit card ones they use. You can read live data on the bigger one. I know the one at airport and m59 uses one. But i dknt think your near waterford.. use facebook. You would be surprised how many people have scanners or access to a friends.
AJ Hall is offline   Reply With Quote
Old August 29th, 2013, 08:03 PM   #30
muddinman56
blood,sweat and beers
 
muddinman56's Avatar
 
Join Date: 10-06-08
Location: armada michigan
Posts: 3,691
iTrader: (18)
Mentioned: 0 Post(s)
Default

Well it's not a tps,iac,maf,or map sensors and is not a vacuum leak?????
muddinman56 is offline   Reply With Quote
Reply
Great Lakes 4x4. The largest offroad forum in the Midwest > 4x4 Talk > Chevy Tech

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

Forum Jump


All times are GMT -5. The time now is 08:03 AM.


Powered by: vBulletin, Copyright 2000 - 2012, Jelsoft Enterprises Ltd.
User Alert System provided by Advanced User Tagging (Lite) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd. Runs best on HiVelocity Hosting.
Page generated in 0.19369 seconds with 51 queries