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Discussion Starter · #1 · (Edited)
About 120K miles, runs perfect. Only about 30,000 miles since buying in 2010. Plugs, wires, everything done 12/10 and periodic maintenance. Never a starting or running problem with engine. A few weeks ago it started stumbling on pulling away from a stop. Last time it died for about 6-8 seconds as I crossed the intersection. I flutter the gas pedal and it recovers....but maybe not next time?? My local shop guy says it could be the throttle body, and to pull it apart and clean it. Not as easy as it sounds, though. Said it would result in a code, but not a problem. I took a code reading, but it says NONE.



























What codes should I look for BEFORE I start pulling things apart??
 

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Discussion Starter · #3 ·
What brand gas are you using, how long has it been in the tank?
I drive this vehicle fairly regularly...once or twice aweek, short trips to MD or stores. Gas is constantly refilled, and I put in 2 bottles of Techron a week ago, but it makes no difference to this issue as far as I can tell. Of course, my injection is direct and does not go through the TB, so that's not helping the TB at all. I have always used "corner station" gas....not the 50 cent higher brand names. Never had a problem. At $3.29 vs $3.69-3.89 and 12-15 mpg around town, I keep my gas costs down. As you can see 30,000 in 10 years (including several trips between Las Vegas and SoCal and NorCal) I don't put many miles on it.
 

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Sometimes spending a little extra is a big savings down the road.
I'm not saying your problem is due to cheap gas; but there are advantages to using "top tier" gas.
For example, you don't need to spend good money on Techron twice a week.
There is a "top tier" gas website, take a look
 

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Discussion Starter · #8 ·
Starts right up, idles smooth, no shuddering or missing. I drove it yesterday to a nearby diner, and when I left it stumbled (actually died for a few seconds) as I was pulling out of the parking lot. I have to cross two sets of railroad tracks, so it's a little scary. I suppose there's a U-tube video on cleaning the TB, but if that's not the problem I don't want to chase ghosts.
 

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It acts like a fuel problem, guys who are familiar with the old systems would tell you to rebuild the carburetor.
Of course, you have fuel injectors and a throttle body. The throttle body just delivers air to the engine! So I don't think it's the throttle body.
However, it doesn't hurt to clean it. I would just remove the air intake housing and spray some TB cleaner into the throttle body without removing it.
Don't pry, or try to move the butterfly, you can turn on the key, don't start the engine, but have someone push the gas pedal to open the butterfly and give it a 2nd spray.
I usually wait a few minutes before I start the engine. It should run fine without codes. Try a test drive.
I'm not one of the guys who 1st look toward fuel pressure; but I think in this case, it's a good spot to look.
When the truck is running, can you smell gas, there could be a fuel leak, the lines will and can rust through?
 

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2000 Silverado Z71 4x4 5.3L 480k+ miles w/ GM rebuilt motor and trans
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I'm not one of the guys who 1st look toward fuel pressure; but I think in this case, it's a good spot to look.
My life has been validated. 😋

The stumbling and dying makes me think weak fuel pump. When mine was going, I would have to sit with my foot bouncing on the gas and the other holding the brake to prepare for jumping into traffic. Talk about nerve racking...
 

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Discussion Starter · #11 ·
My life has been validated. 😋

The stumbling and dying makes me think weak fuel pump. When mine was going, I would have to sit with my foot bouncing on the gas and the other holding the brake to prepare for jumping into traffic. Talk about nerve racking...
I was considering the fuel pump. No fuel smell or anything unusual, but I know these units don't last forever. I get plenty of power when I pull on the freeway and punch it, but I'm not sure that tells me anything.

The more I think about it, when it does "die" when gently accelerating away from a stop maybe just letting off the pedal lets it "restart"....not necessarily fluttering the pedal. I'd have to try it next time it happens, but I may be on the tracks or in the middle of an intersection with someone right on my bumper. :O.

It's kinda rainy today (always welcome in dry NorCal), and there's two football games today, so I might stay in and do more research instead of maybe getting stuck on the road somewhere. :(
 

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Discussion Starter · #12 ·
It acts like a fuel problem, guys who are familiar with the old systems would tell you to rebuild the carburetor.
Of course, you have fuel injectors and a throttle body. The throttle body just delivers air to the engine! So I don't think it's the throttle body.
However, it doesn't hurt to clean it. I would just remove the air intake housing and spray some TB cleaner into the throttle body without removing it.
Don't pry, or try to move the butterfly, you can turn on the key, don't start the engine, but have someone push the gas pedal to open the butterfly and give it a 2nd spray.
I usually wait a few minutes before I start the engine. It should run fine without codes. Try a test drive.
I'm not one of the guys who 1st look toward fuel pressure; but I think in this case, it's a good spot to look.
When the truck is running, can you smell gas, there could be a fuel leak, the lines will and can rust through?
See my post to OpalLacod. :)
 

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Discussion Starter · #13 ·
Stumbling/dying has been worse lately so I took another DTC scan. Nothing!

One member said he had solved the issue after doing all the expensive things that did not work...had the dealer mess with it for 2-3 days, and they came back with a diagnosis and FIX by cleaning or replacing a ground wire connection for the coil packs that grounded at the4 front of the block by the crank pulley. I tried to follow up with him, but never got a reply. HAS ANYONE ELSE SOLVED THIS ISSUE WITH THIS METHOD???
 

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does this truck have a vacume brake booster? it kind of sounds like a leaky brake booster... stalling while leaving a stop sign or after holding the brake for.an extended period of time.

you can test this with an obd2 scanner, watch the short term and long term fuel trims while you hold the brakes. they will rise all the way up to 100% if you hold the brakes long enough. the ECU compensates for the vacume loss and when you let off the brakes and it suddenly returns the truck will stumble and possible stall.

it's worth investigating anyways, especially of you have a vacume brake booster. I have no idea if you do or not.
 

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Discussion Starter · #16 ·
does this truck have a vacume brake booster? it kind of sounds like a leaky brake booster... stalling while leaving a stop sign or after holding the brake for.an extended period of time.

you can test this with an obd2 scanner, watch the short term and long term fuel trims while you hold the brakes. they will rise all the way up to 100% if you hold the brakes long enough. the ECU compensates for the vacume loss and when you let off the brakes and it suddenly returns the truck will stumble and possible stall.

it's worth investigating anyways, especially of you have a vacume brake booster. I have no idea if you do or not.
Definitely has the power brake vacuum booster. I just did another OBDII scan and got "0" codes or diagnostic comments. Brakes work normally.....exceptionally I think, given that they have been the same pads as when I bought the Sub in 2010. But that's only about 33,000 miles. Still...it is a heavy truck. (?) Have had the rear E-brake system repaired several times. :(
 

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do you know if you have a hydroboost or a vacume brake booster?

can you look at live data with your obd2 scanner? if you can, watch the short term and long term fuel trims with your foot off the brake and then while holding the brakes. if the fuel trims start rising then that is a good diagnoses of a vacume leak in a vacume brake booster.

if you have a hydroboost brake booster than that does not apply at all.
 

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Discussion Starter · #18 ·
My life has been validated. 😋

The stumbling and dying makes me think weak fuel pump. When mine was going, I would have to sit with my foot bouncing on the gas and the other holding the brake to prepare for jumping into traffic. Talk about nerve racking...
You're right.....that would be scary! But I don't think it's a fuel issue because it just dies without any real warning like coughing. Yesterday I made my typical shopping route to several stores about 3 miles from home. It died/hesitated several times along the way. So, about halfway back I watched the tach to see what was happening when it "died". Of course, I expected to see the tach drop to "0". OF COURSE....it didn't stumble or die once the rest of the way through at least 6 STOP signs and 4 red lights. NOT ONCE! :( I'll try again today.
 

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Discussion Starter · #19 ·
do you know if you have a hydroboost or a vacume brake booster?

can you look at live data with your obd2 scanner? if you can, watch the short term and long term fuel trims with your foot off the brake and then while holding the brakes. if the fuel trims start rising then that is a good diagnoses of a vacume leak in a vacume brake booster.

if you have a hydroboost brake booster than that does not apply at all.
OK. Looking at my simple Haynes manual I see two procedures for testing both the vacuum booster and the hydraulic booster. But I don't know which I have or how to tell them apart.
 

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Discussion Starter · #20 ·
My life has been validated. 😋

The stumbling and dying makes me think weak fuel pump. When mine was going, I would have to sit with my foot bouncing on the gas and the other holding the brake to prepare for jumping into traffic. Talk about nerve racking...
I am more considering an ignition/electrical circuit issue because there is no symptom of fuel slowing down or getting blocked before it just "dies". A grounding or electrical interruption would be immediate like it seems to do. The "guess" gives me no idea what I'm doing....or not doing....to bring the engine back to life. Couldn't be a transmission problem, could it?
 
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