Jump to content

2004 Silverado 5.3L Vin T Idles low

DDGLDO
 Share

Recommended Posts

DDGLDO Enthusiast

DDGLDO

Posted
Posted (edited)

I am the proud owner of a 2004 Silverado Crew Cab truck with 210276 miles on the clock and no check in light or trouble codes...  truck has been really great since I bought it new.  I now have a problem where I get an extremely rough idle after driving at highway speeds and stopping at a ramp light when exiting.  I am worried because a few times the truck backfired and nearly died on me.  I have replaced the O2 sensors (All of them)at the start of these issues as they were original to the truck. I have also cleaned the throttle body and replaced the spark plugs.  Using my data logger I can see that the throttle is at 4 to 5% at idle in the driveway at 525-560 rpms (fluctuating rapidly).  I have looked for vacuum leaks and found none.  I am thinking that my Throttle Position Sensor may be about to give up the ghost.  What do you guys think based off of the information I have provided here?  If you need more let me know please. 

 

List of new parts installed in order before and after trouble started:

battery (Just before issues started)

O2 sensors (all after issues started)

Plugs (After)

Plug wires inspected, no apparent damage and less than 1 year old

Throttle body removed and cleaned on the bench (After and last thing I have done before this post).

 

 

Thank you in advance!

 

Edited by DDGLDO
Add to title
  • DDGLDO changed the title to 2004 Silverado 5.3L Vin T Idles low
richard wysong Senior Enthusiast

richard wysong

Posted
Posted

try doing the idle relearn procedure. when you changed the bat you lost memory. it sometimes has to be done after a throttle clean as well. also try cleaning the idle air control and make sure the pintle moves. did you check with a scan tool or just a code reader?

richard wysong Senior Enthusiast

richard wysong

Posted
Posted

as it all started when you changed the bat make sure any wiring, grounds in that area didn't get damaged

DDGLDO Enthusiast

DDGLDO

Posted
  • Author
Posted (edited)

Richard,

Thank you for the reply!  I used my handheld scanner to check for the DTCs.  I did disconnect the battery again, let the truck idle for 5 minutes, turned it off for about a minute and then started it again to idle for another five.  After turning it off for about 20 minutes (Long enough to change my pants and grab my wallet) I took it on a thirty mile drive at highway speeds.  As for the IAC, I don't think my truck has that...   I thought the problem may have been resolved until I was on my way home and noticed it doing it again.  Call me crazy but I think it even did while under acceleration up a hill.  

 

I will go out and take a closer look for anything amiss around the battery and let you know if there is anything going on there.

 

Thanks again!

Edited by DDGLDO
Answered question about IAC
richard wysong Senior Enthusiast

richard wysong

Posted
Posted

it has an IAC somewhere in the area of the throttle. thats how the pcm controls idle speed. has a 3 wire connector and 2 screws holding it to the throttle body. the way it works is it screws the pintle in and out to control basicly a vacuum leak that raises and lowers the rpm to the pcm command. they get stuck occasionly and may not set a code. if your scanner does data you should see the counts start high when you start it and slowly decrease. when you take it out to clean it and the passages it sits in you will probably find it fully extended, clean it and then screw/push the pintle in before reinstalling. when you start it the idle should be higher than normal but quickly decrease, if it doesn't its probably NG

CamGTP Senior Enthusiast

CamGTP

Posted
Posted

Trucks with electronic throttle bodies do not have an IAC. The idle it controlled by the blade itself.

 

Off hand I don't know what the throttle percent should be at idle but I thought it should be at 5% or more.

 

A throttle relearn is still a good idea. I'd double check fuel pressure at idle as well. Clean the MAF too.

 

And see what your fuel trims are doing while at idle and driving. Lots of negative trims means it's pulling fuel and positive trims means it's having to add in fuel to make it happy.

  • Like 1
richard wysong Senior Enthusiast

richard wysong

Posted
Posted

learn something new everyday. thank you for correcting me. what year did they start electronic throttle control?

CamGTP Senior Enthusiast

CamGTP

Posted
Posted

Depends on what trim you have.


They used it in as early as 2001 in the trucks like the Denali. Some Silverado/Sierra's have it in 2001-2002 as well if they have the advanced traction control system in them but not many had that. They went full time drive by wire in 2003 with the 4.8/5.3/6.0 in all trucks. The 4.3 stayed cable driven for a few years yet and same with the commercial vans like the express.

 

Corvettes have been DBW since 1997.

DDGLDO Enthusiast

DDGLDO

Posted
  • Author
Posted
2 hours ago, CamGTP said:

Trucks with electronic throttle bodies do not have an IAC. The idle it controlled by the blade itself.

 

Off hand I don't know what the throttle percent should be at idle but I thought it should be at 5% or more.

 

A throttle relearn is still a good idea. I'd double check fuel pressure at idle as well. Clean the MAF too.

 

And see what your fuel trims are doing while at idle and driving. Lots of negative trims means it's pulling fuel and positive trims means it's having to add in fuel to make it happy.

CamGTP,

Thanks for the info!  I will take a look on my way to work tomorrow how the fuel trim looks.  Just at idle both were at 2.  Just redid the throttle relearn tonight.  

 

Thanks again!

dna9656 Enthusiast

dna9656

Posted
Posted (edited)

Ya know Richard, I don't understand why it takes repeated tries to get the ECM to relearn. It's a bunch of chips fercryinoutloud!

Edited by dna9656
  • Haha 1
richard wysong Senior Enthusiast

richard wysong

Posted
Posted

ya got me, could be it doesn't see all the data parameters on the first pass? Im not saying everytime it has to be done twice but from experience if it doesn't fix it the first time try it again before moving up the tree

  • Like 1

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.4k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,759
    Total Members
    8,960
    Most Online
    DM22
    Newest Member
    DM22
    Joined

  • Who's Online   2 Members, 0 Anonymous, 2,964 Guests (See full list)

  • Latest Articles

  • Posts

    • B14Sierra
      Cam chain tensioner question

      By B14Sierra · Posted

      So I'm in the middle of a DOD AFM delete on my 6.2 L86 Sierra. I had a pick holding the tensioner but after I got the Cam phaser gear off I was cleaning off all the rtv and apparently I didn't have the pick seated far enough in. I bumped it and the tensioner sprang forward.  I think everything is good but I want a second opinion. The top of the tensioner is just a looped piece of plastic that rides in that channel right? There is no spring or anything is there? I got the gear and chain back on and it seems tight and everything looks right. I'm hoping nothing fell out.
    • dna9656
      No low range 4 x 4

      By dna9656 · Posted

      My 2015 1500 LTZ Silverado suddenly won't go into 4 x 4 low. It will go into 4 x 4 high.
    • asilverblazer
      Transmission Woes :-(

      By asilverblazer · Posted

      Yep, just a quick reference point.    My main point being I’d do a thousand other things before I’d pay 10k for a transmission.    Speaking in ignorance cause I don’t look at these trucks, what is it worth? 20k?
    • asilverblazer
      Intermittent no-code issues on 2022.5+ V8 trucks — what did the shop fail to capture?

      By asilverblazer · Posted

      I think users are going to want to pick their monitored parameters, which parameters they want to see first.    It should probably start with baseline at a minimum and adjust to learned, but be able to overlay baseline for comparison.   A simple severity level would be able to determine what type of alerting is appropriate or user selectable.    Why not use the OBD port though?   I think a phone connection would be a good idea, push notifications type deal.   Number 1 issue is having data is useless if you don’t know what the data should be under normal conditions. 
    • Chuck FB
      summer road trips in the 2026 2500HD

      By Chuck FB · Posted

      I thought I would use your thread and add to it as I just did my first longer drive with my truck in the last couple of days. I drove from the Grande Prairie area of Alberta down to Edmonton and most of where I drove in the city was the ring road so fairly free flowing but a bit of stop and go as well in the city. Stayed the night and returned home and not too many stops along the way each way but every restart and certainly every cold start sets it back for fuel mileage. Why I say that is I see some people will cherry pick a fuel mileage leg after the vehicle had been warmed up driveline wise before hand and its a forgiving ( easy rolling drive leg for example ) and call that their fuel mileage which can give a false perception of reality. I was not heavily loaded at all but never the less the flip bak cover, rubber bed mat, various tools etc and extra jerry cans of fuel all way up to a few hundred pounds of dead weight so its not an empty truck. The cold inflation tire pressures are set more near the freezing point so once they are warmed up driving I was showing 45 front and over 40 rear and realize high inflation pressures would help a little in fuel mileage but certainly not the ride on our crap sections of highway. The weather was good so was not raining as that can really drag mileage down, in fact I had a bit of a tail wind on average driving home. Most people on here would never have driven on that freeway to visualize it but its got a fair bit of rolling type of landscape with numerous river valleys. For the most part I had it on cruise set to 62 although kicking it off if I caught it in time before it started down shifting and self braking going down the grades. Most of the more substantial grades its shifting into 7th I believe as 8th just doesn't have it. Total distance round trip was 643 miles and my overall average and I did refuel three times in all, figured out to 17.65 miles per US gallon. My best fuel mileage section refuel within all of this figured out to 18.46 and these are all hand calculated figures. I find if anything that the trucks computer can be over optimistic, sometimes its pretty close but other times its stretching it. On paper persay in theory the truck would have just about made it on fumes for that whole drive without refueling once.    Which made me think of the topic thread of the wonder if these trucks could do 20 mpg and that is a good question, certainly would have to be on an easy going flat highway, no head wind, the right temperature, not packing around a bunch of dead weight and puttering along even slower than I was I would suspect and going steady and not stopping to smell the flowers or take a piss !. It probably is possible but not without effort to attain that with the wind resistance and weight of these trucks. Of course on my drive most people are passing me if they have the power as per loaded highway tractors, never mind a lot of speedy vehicles but the speed limit is 68 and most are at or well over that. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...