Reply
Go Back   TexasBowhunter.com Community Discussion Forums > Topics > Around the Campfire
 
Thread Tools Display Modes
Old 04-06-2018, 12:26 AM   #1
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default Mechanic Help!!!

Ok mechanics I need some help. I have a 1998 gmc 1500 5.7l 350 that I had to replace the heads on. I replaced the heads and every gasket/o ring from the heads up. After conpleting the install the truck runs very smooth and sounds good. Howeer it will not drop below 2500rpms at idle. After doing some research I have gone as far as to tear it back down to check the intake gaskets again to make sure they set good and re siliconed the ends. Other things replaced are all 4 O2 sensors, IAC sensor, pcm hose, all new plugs and wires. After the second time in I cranked it and it does the exact same thing. Fires right up but sits a contamt 2500 rpm. Pleae let me know if you have any suggestions or knowledge with this issue. Thanks for any help in advance.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-06-2018, 02:49 AM   #2
pervis
Ten Point
 
Join Date: Jul 2015
Default

Had something similar one time w a 350 vortec. I didn't give the lifters an oil bath b4 installing em. Took em out, soaked em 're install, ran like a top
pervis is offline   Reply With Quote Back To The Top
Old 04-06-2018, 04:52 AM   #3
91cavgt
Ten Point
 
91cavgt's Avatar
 
Join Date: Jun 2013
Location: Waco
Default

Double check your vacuum lines. You just moved a whole bunch of 20 year old brittle hoses around in the process of removing the intake.
91cavgt is offline   Reply With Quote Back To The Top
Old 04-06-2018, 05:14 AM   #4
Goldeneagle
Pope & Young
 
Goldeneagle's Avatar
 
Join Date: Oct 2006
Location: Allen, TX
Hunt In: Where ever I get a chance.
Default

Quote:
Originally Posted by 91cavgt View Post
Double check your vacuum lines. You just moved a whole bunch of 20 year old brittle hoses around in the process of removing the intake.
This^^^^^. And check the throttle cable and make sure it is in the proper spot.
Goldeneagle is offline   Reply With Quote Back To The Top
Old 04-06-2018, 07:01 AM   #5
Texas Tracker
Pope & Young
 
Texas Tracker's Avatar
 
Join Date: Nov 2006
Location: Wimberley Texas/Hunt every place I can!
Default

Quote:
Originally Posted by 91cavgt View Post
Double check your vacuum lines. You just moved a whole bunch of 20 year old brittle hoses around in the process of removing the intake.
Start with the vacuum lines then replace your idle control sensor and check wires going to it.

https://www.bing.com/videos/search?q...D3EC&FORM=VIRE
Texas Tracker is offline   Reply With Quote Back To The Top
Old 04-06-2018, 07:03 AM   #6
WTucker
Eight Point
 
WTucker's Avatar
 
Join Date: Aug 2016
Location: Orangefield
Hunt In: Mauriceville
Default

Possible vacuum leak
WTucker is offline   Reply With Quote Back To The Top
Old 04-06-2018, 07:27 AM   #7
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Ok so idle sensor has been replaced and i have wore myself out searching vacuum lines. A buddy hooked his computer to it and cannot see anything out of the normal on the readings. If it was a vacuum issue would it have some variences in the idle? It is spot on 2500 rpms and does not fluctuate much at all.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-06-2018, 07:44 AM   #8
BETTERLUCKYTHANGOOD
Ten Point
 
BETTERLUCKYTHANGOOD's Avatar
 
Join Date: Feb 2007
Location: Liberty hill
Hunt In: Have bow will travel
Default

Is the truck TBI or TPI?
TBI, check the gasket under the Throttle body and make sure the line going to the brake booster is hooked up correctly.....I would plug that line just to rule out a bad brake booster.
TPI, make sure the fuel lines inside the intake aren't leaking, we called that the octopus. I've also seen the fuel pressure regulator on that system leak and cause high idle.
But i'd put my money on a vacuum leak.
BETTERLUCKYTHANGOOD is offline   Reply With Quote Back To The Top
Old 04-06-2018, 07:49 AM   #9
Radar
Ten Point
 
Radar's Avatar
 
Join Date: Jul 2016
Location: Wilson County
Hunt In: Wilson County
Default

Do you have a plastic intake manifold?
Radar is offline   Reply With Quote Back To The Top
Old 04-06-2018, 08:34 AM   #10
miket
Pope & Young
 
miket's Avatar
 
Join Date: Oct 2008
Location: Plantersville
Hunt In: Grimes County, Victoria
Default

Quote:
Originally Posted by IAFFHunter18 View Post
Ok so idle sensor has been replaced and i have wore myself out searching vacuum lines. A buddy hooked his computer to it and cannot see anything out of the normal on the readings. If it was a vacuum issue would it have some variences in the idle? It is spot on 2500 rpms and does not fluctuate much at all.
I dont know if they worked the same in 1998, but when I replaced my wifes 2009 Tahoe Throttle Body it did that. Was crazy. I read that even cleaning it or moving it at all could cause the issue. Most said turning off and on and letting it run would make the computer re-calibrate but it wouldnt. Ended up having to take to dealer and they re flashed it ( whatever that means ) and it went straight down to normal. Was like $99
miket is online now   Reply With Quote Back To The Top
Old 04-06-2018, 08:47 AM   #11
txhunter-1
Four Point
 
txhunter-1's Avatar
 
Join Date: Feb 2018
Location: Texas
Hunt In: Texas
Default

Sounds like everyone else said, vacuum lines and rule out the brake booster. Take you a can of starting fluid (ether) and simply spray it in areas that may be pulling a vacuum, like the brake booster and large vacuum lines. When spraying, if it idle increases and increases the idle, you have pinpointed the issue/location. Good luck...
txhunter-1 is offline   Reply With Quote Back To The Top
Old 04-06-2018, 09:09 AM   #12
mastercraftka
Eight Point
 
mastercraftka's Avatar
 
Join Date: Oct 2016
Location: TEXAS
Hunt In: South Texas
Default

Totally agree with the vac leak possibility easy and cheap to eliminate that option first before anything else.
mastercraftka is offline   Reply With Quote Back To The Top
Old 04-06-2018, 09:36 AM   #13
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Quote:
Originally Posted by Radar View Post
Do you have a plastic intake manifold?
Yes sir, checked it for leaks, sprayed all around it and found nothing. Also replaced the gaskets there as well.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-06-2018, 09:39 AM   #14
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Does anyone know how many vacuum lines there are? Just want to make sure I am checking them all. I may also add that it did not do this prior to replacing the cracked head and gaskets. This started after all this.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-06-2018, 10:20 AM   #15
Rubberdown
Eight Point
 
Join Date: May 2015
Location: Houston
Default

Did you try the ole starting fluid or whatever spray in various spots and see if the idle fluctuates.... helps you find your leak. That's what I always do to find leaks.

Ryan
Rubberdown is online now   Reply With Quote Back To The Top
Old 04-06-2018, 10:40 AM   #16
mastercraftka
Eight Point
 
mastercraftka's Avatar
 
Join Date: Oct 2016
Location: TEXAS
Hunt In: South Texas
Default

Quote:
Originally Posted by Rubberdown View Post
Did you try the ole starting fluid or whatever spray in various spots and see if the idle fluctuates.... helps you find your leak. That's what I always do to find leaks.

Ryan
This would be very wise to do as well!! wd40 works also.
mastercraftka is offline   Reply With Quote Back To The Top
Old 04-06-2018, 10:49 AM   #17
heyearl
Eight Point
 
heyearl's Avatar
 
Join Date: Oct 2006
Location: Pasadena, Texas
Hunt In: Cleveland
Default

SMOKE
https://www.youtube.com/watch?v=Np_duzsaZxI
heyearl is online now   Reply With Quote Back To The Top
Old 04-06-2018, 11:18 AM   #18
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Quote:
Originally Posted by mastercraftka View Post
This would be very wise to do as well!! wd40 works also.
Yes sir, I have gone through about 4 cans lol
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-06-2018, 11:30 AM   #19
kurt68
Ten Point
 
kurt68's Avatar
 
Join Date: Oct 2006
Hunt In: Montgomery Co. and Rocksprings and "H"
Default

I would double check the throttle cable, sounds like it's kinked or hung up some how.
kurt68 is offline   Reply With Quote Back To The Top
Old 04-06-2018, 12:09 PM   #20
silentstalker92
Six Point
 
silentstalker92's Avatar
 
Join Date: Nov 2017
Hunt In: votaw
Default

smoke test it

https://www.popularmechanics.com/car...a-vacuum-leak/
silentstalker92 is offline   Reply With Quote Back To The Top
Old 04-06-2018, 12:39 PM   #21
bwssr
Pope & Young
 
bwssr's Avatar
 
Join Date: Oct 2006
Location: Madisonville, Texas
Hunt In: Madison county
Default

Quote:
Originally Posted by kurt68 View Post
I would double check the throttle cable, sounds like it's kinked or hung up some how.
This or the TPS is nit bolted right
bwssr is offline   Reply With Quote Back To The Top
Old 04-06-2018, 02:37 PM   #22
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Ok. Cables are good. Both have slack when let off. Checked the TPS position its good. This thing has me stumped!!!!!! I have asked several mechanic buddies and no one can figure this out. I dont get it.....
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-06-2018, 04:45 PM   #23
miket
Pope & Young
 
miket's Avatar
 
Join Date: Oct 2008
Location: Plantersville
Hunt In: Grimes County, Victoria
Default

Did you do any kind of TPS relearn? Looks like procedured vary based on year. ( cable vs wire etc )
miket is online now   Reply With Quote Back To The Top
Old 04-06-2018, 04:49 PM   #24
miket
Pope & Young
 
miket's Avatar
 
Join Date: Oct 2008
Location: Plantersville
Hunt In: Grimes County, Victoria
Default

Looks like may need to do tps relearn

https://ls1tech.com/forums/pcm-diagn...learn-tps.html

Apparently its different than with our Tahoe, but same concept
miket is online now   Reply With Quote Back To The Top
Old 04-06-2018, 08:02 PM   #25
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Quote:
Originally Posted by miket View Post
Looks like may need to do tps relearn

https://ls1tech.com/forums/pcm-diagn...learn-tps.html

Apparently its different than with our Tahoe, but same concept
No sir, I have not tried this one but will. I greatly appreciate any and all the help all of you have provided so far. This one has stumped several of us.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-06-2018, 08:25 PM   #26
540 MM
Four Point
 
Join Date: Aug 2011
Location: Lake Jackson Texas
Hunt In: Bandera Texas
Default

Make sure to ck the ground wires at tstat housing. Recommend cutting and installing new eyelet terminal to this. When you pulled the intake did you remove the injectors out of their respective ports?
540 MM is offline   Reply With Quote Back To The Top
Old 04-07-2018, 02:35 PM   #27
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

No sir, didnt mess with the injectors at all. Left them in place.. Checked the ground there and the 2 on the back on the motor and all are hooked up.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-07-2018, 02:38 PM   #28
krisw
Pope & Young
 
krisw's Avatar
 
Join Date: Sep 2009
Location: Hughes Springs, TX
Hunt In: Cass County
Default

Quote:
Originally Posted by 540 MM View Post
Make sure to ck the ground wires at tstat housing. Recommend cutting and installing new eyelet terminal to this. When you pulled the intake did you remove the injectors out of their respective ports?


Doesnít that truck have a spider injection setup? I didnít think you could remove the individual injectors on that.
krisw is online now   Reply With Quote Back To The Top
Old 04-07-2018, 03:16 PM   #29
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Quote:
Originally Posted by krisw View Post
Doesnít that truck have a spider injection setup? I didnít think you could remove the individual injectors on that.
Yes sir, has the ďspiderĒ injectors. I did not remove these just the housing and replaced the gaskets with new ones.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-07-2018, 10:39 PM   #30
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Anyone else with some ideas??? I have hit a wall mentally on this one.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-07-2018, 11:08 PM   #31
krisw
Pope & Young
 
krisw's Avatar
 
Join Date: Sep 2009
Location: Hughes Springs, TX
Hunt In: Cass County
Default

Does it sound like itís revving at 2500 rpm, or is the tach showing that? Could be a loose connection or something like that for the tach.
krisw is online now   Reply With Quote Back To The Top
Old 04-08-2018, 06:09 AM   #32
Goldeneagle
Pope & Young
 
Goldeneagle's Avatar
 
Join Date: Oct 2006
Location: Allen, TX
Hunt In: Where ever I get a chance.
Default

Quote:
Originally Posted by krisw View Post
Does it sound like itís revving at 2500 rpm, or is the tach showing that? Could be a loose connection or something like that for the tach.
Could be this. Is it actually running 2500rpm or just what the tach is showing? I have a '93 1500 and my gauges are starting to do goofy things. I need to remove the cluster and check the wiring on it.
Goldeneagle is offline   Reply With Quote Back To The Top
Old 04-08-2018, 06:39 AM   #33
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Oh no it definately is reving at that. But I can go to D,R,3,2,1 and it idles down. P or N is revs back up.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-08-2018, 06:44 AM   #34
6.5 shooter
Eight Point
 
6.5 shooter's Avatar
 
Join Date: Jan 2017
Default

Check the o-ring where the brake booster locks on to the manifold.
6.5 shooter is offline   Reply With Quote Back To The Top
Old 04-08-2018, 07:05 AM   #35
540 MM
Four Point
 
Join Date: Aug 2011
Location: Lake Jackson Texas
Hunt In: Bandera Texas
Default

Yes, has the spider injector set up however it is poss to pull injectors up out of port and install in incorrect location. Have seen this a bunch of times from local shops incl dealerships causing erratic idle, random misfire faults etc. Since you left them alone, ck oring around injector pass thru connection. Make sure no debris made it down throttle body affecting blade travel. How did you stab distributor?? Remember dist is only for cam reference with that being said you must set initial dist location with scan tool. You have to initiate it and set it. Even if u marked dist before you removed u must set it with scan tool! Cam retard will make idle stick due to base idle timing fail!
540 MM is offline   Reply With Quote Back To The Top
Old 04-08-2018, 07:14 AM   #36
540 MM
Four Point
 
Join Date: Aug 2011
Location: Lake Jackson Texas
Hunt In: Bandera Texas
Default

How did u adjust valves? Why did u replace heads? Where did u get heads? What are ur head and intake gasket part numbers? Just trying to help
540 MM is offline   Reply With Quote Back To The Top
Old 04-08-2018, 09:27 AM   #37
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Ok ill do my best at answering...... distributer was marked and reinstalled by a a mechanic buddy who also set the timing with his scan tool. I had a bad intake gasket leak on the ds and the ps head had several cracks. So I replaced both of them with new heads and complete new gasket set. Not sure on model number on the gaskets but after it was all done and the idle did what it did and we checked everything else, i figured crap maybe we got something off or not set right so we went all the way back down a second time replacing the gaskets again and still no change. The heads, valve springs, all the hardware was replaced with new parts and adjusted by a well known and respected local motor guy. What I dont understand is that running it sounds really good, smooth, no ticking, no missing, etc. just idles high in park. Im lost.......
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-08-2018, 09:30 AM   #38
krisw
Pope & Young
 
krisw's Avatar
 
Join Date: Sep 2009
Location: Hughes Springs, TX
Hunt In: Cass County
Default

My 97 z71 will idle kinda high in park sometimes. Usually around 1000 rpm or so. But only when I first crank it and itís cold.
krisw is online now   Reply With Quote Back To The Top
Old 04-09-2018, 12:37 PM   #39
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Ok changed changed/checked all vacuumm lines and orings. Still cranks up and runs very smooth. Just idles at 2500 rpms. I dont get it. Just left it with a mechanic that has a computer.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-09-2018, 12:51 PM   #40
mastercraftka
Eight Point
 
mastercraftka's Avatar
 
Join Date: Oct 2016
Location: TEXAS
Hunt In: South Texas
Default

Isn't there an idle sensor on that year model? So when it is cold it revs up and then after it warms up it goes back down?
mastercraftka is offline   Reply With Quote Back To The Top
Old 04-09-2018, 02:17 PM   #41
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Quote:
Originally Posted by mastercraftka View Post
Isn't there an idle sensor on that year model? So when it is cold it revs up and then after it warms up it goes back down?
Im not sure. If your talking about the Idle Air Control sensor then I have replaced that one with know change. Unless I am missing something which is highly possible, everything else I have found has to be adjusted electronically.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-09-2018, 03:06 PM   #42
BIGTERRY75
Ten Point
 
BIGTERRY75's Avatar
 
Join Date: Sep 2012
Location: Rockwall
Hunt In: Van Zandt, Bosque, Rockwall
Default

From a mechanic....................

















Take it to a mechanic.
BIGTERRY75 is offline   Reply With Quote Back To The Top
Old 04-09-2018, 03:06 PM   #43
kurt68
Ten Point
 
kurt68's Avatar
 
Join Date: Oct 2006
Hunt In: Montgomery Co. and Rocksprings and "H"
Default

Could you have bent the control arm on the throttle body? I know i was doing work on my old truck and it was idling high, I bent the bracket barely that the throttle cable rested against with the adjusting screw. Might check that or if it has that kind of set up.
kurt68 is offline   Reply With Quote Back To The Top
Old 04-09-2018, 03:35 PM   #44
kingranch
Ten Point
 
kingranch's Avatar
 
Join Date: Dec 2010
Location: austin
Default

u sure throttle body butterfly isnt getting stuck slightly open? I could see this happening and the load when in gear is enough to keep the engine loaded down a bit-
try wiping the inside of the tb out with rag that was soaked in tb cleaner esp around the contact points
kingranch is offline   Reply With Quote Back To The Top
Old 04-09-2018, 07:38 PM   #45
540 MM
Four Point
 
Join Date: Aug 2011
Location: Lake Jackson Texas
Hunt In: Bandera Texas
Default

Need more info; short term fuel trim correction, IAC counts, minimum TPS voltage, desired idle with actual idle rpm that ECM is seeing or commanding, O2 voltages and swings, etc. To properly diagnose a prob u need proper tools. JMO.
540 MM is offline   Reply With Quote Back To The Top
Old 04-09-2018, 07:42 PM   #46
Radar
Ten Point
 
Radar's Avatar
 
Join Date: Jul 2016
Location: Wilson County
Hunt In: Wilson County
Default

Quote:
Originally Posted by BIGTERRY75 View Post
From a mechanic....................

















Take it to a mechanic.
Had to laugh
Radar is offline   Reply With Quote Back To The Top
Old 04-09-2018, 09:10 PM   #47
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Quote:
Originally Posted by Radar View Post
Had to laugh
Ok pretty good there sir......

I did so we will see. I will say I have had 2 really good mechanics involved in this and both are stumped as well. Hoping something simple.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-09-2018, 09:12 PM   #48
IAFFHunter18
Six Point
 
IAFFHunter18's Avatar
 
Join Date: Sep 2014
Location: Lindale
Hunt In: East Texas, Sonora
Default

Quote:
Originally Posted by kingranch View Post
u sure throttle body butterfly isnt getting stuck slightly open? I could see this happening and the load when in gear is enough to keep the engine loaded down a bit-
try wiping the inside of the tb out with rag that was soaked in tb cleaner esp around the contact points
Tried this this morning. I had that sucker polished up nice!!! Still no change. I will let yall know for future reference what they find.
IAFFHunter18 is online now   Reply With Quote Back To The Top
Old 04-12-2018, 06:08 PM   #49
kurt68
Ten Point
 
kurt68's Avatar
 
Join Date: Oct 2006
Hunt In: Montgomery Co. and Rocksprings and "H"
Default

Update?
kurt68 is offline   Reply With Quote Back To The Top
Old 04-26-2018, 03:21 PM   #50
miket
Pope & Young
 
miket's Avatar
 
Join Date: Oct 2008
Location: Plantersville
Hunt In: Grimes County, Victoria
Default

Quote:
Originally Posted by kurt68 View Post
Update?
X2. Would love to know how it turned out
miket is online now   Reply With Quote Back To The Top
Reply

Thread Tools
Display Modes

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 09:26 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2018, vBulletin Solutions Inc.
Copyright 1999-2012, TexasBowhunter.com