Stalls at idle

Tiny
RMSPARKS1343
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 4WD
  • AUTOMATIC
  • 69,000 MILES
I hear the fuel pump working and it will start up but won't hold an idle then it will die. When I give it gas it has a delayed response, it won't hold as I rev the engine and it will die. I filled up the gas tank about 2-3 days prior to this and it was running fine for those few days. It acts like it gets flooded when I give it gas. I usually add Heat to the gas but I stopped about a month ago.
Friday, May 9th, 2014 AT 5:14 PM

14 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Is the check engine light staying on? If so, have you scanned the computer? Have you checked fuel pump pressure? Even though the pump is running, it may not be producing enough pressure or the regulator could be bad and too much pressure is being supplied.

Let me know what point you are at in diagnosing the issue.
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
RMSPARKS1343
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The check engine light is on when the key is in the run position. It wasn't on before. I do not have accesses to a computer to diagnose it. I have a mechanic friend who is going to help me check the fuel pump pressure tonight.

I'll reply again once we get a reading on the pressure. What should the PSI read?
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
JACOBANDNICKOLAS
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What size engine is in the vehicle?
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
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I need to shut down for right now. The most common engine is the 5.3L V8 in your vehicle. If that is correct, the KOEO fuel pressure should be 55-62 psi.
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
RMSPARKS1343
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So we checked and we had NO pressure. We could hear something clicking back by the tank but after we hooked up the pressure gauge and saw no movement on that needle we figured it's got to be the pump. Do you recommend that we change the fuel filter too?

We checked the relay and it was fine. We couldn't find what fuse went to the pump.

Thanks!
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
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Hi, I'm back. Sorry I had to leave last night, but 4am comes really fast. As far as the problem, there should be a main fuel pump fuse under the hood. Check that. If it is good, then remove the tank and confirm that there is power to the fuel pump. If there is, then the pump is bad and will need replaced.

Let me know if you have questions or need help with anything.

Joe
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
RMSPARKS1343
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We are pretty sure it's the pump. The previous owner agrees it's about time to change the fuel filter and pump. Also, the mechanic friend recalls changing it out last time this happened.

Thanks for all the help. If anything comes up while we replace I'll be sure to follow up here. This is a great site!
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
JACOBANDNICKOLAS
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I'm glad to help. Let me know how things go for you.

Also, before you purchase a new fuel pump, make sure to check if there is power to the harness at the pump. It could even be a fuel pump relay that is bad and that is a much, MUCH cheaper part.

Joe
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
RMSPARKS1343
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Joe,

I changed the fuel pump, we can hear the pump working when we cycle the key, which was something we didn't hear before. We also changed the fuel filter. When we removed the old filter there was a lot of dark, almost black, watery gas that poured out of the filter. We did not check the pressure of the pump once we replaced the pump, so I'm not sure if the pump is putting out enough pressure.

Once we had everything back together we started the truck and it fired right up. I drove it out of the shop and parked it and turned it off, everything was fine. After about 3 min (I cleaned up the shop) I took it out on the road to test it out. I ran fine but as I slowed down to turn a corner, it would drop RPM's down to about 400. My truck struggled to hold the idle. I drove out a little further and again making a turn I loss RPM's and it died mid turn.

I'm going to check the PSI to make sure its sending out 55-62 PSI. My question is, what should I look for next if we have the right amount of pressure? It has a full tank of gas. We are also going put a siphon down to the bottom of the tank to see if we have clean gas.

Any suggestions are greatly appreciated.

Thank you,
Rhonda
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
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Rhonda:

Hi. Sorry you are having trouble again. Listen, what was in the old fuel filter has me a big concerned. Have you tried to remove the new one to see if it is dirty too? Also, how far did you drive the truck (totally)? Could you possibly have water or dirt in the fuel line still? When it stalled on you, did it start back up?

Let me know. Also, if you check the fuel pump pressure, let me know what you find. I'm starting to think something may be in the fuel tank and causing problems.
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
RMSPARKS1343
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Joe,

Yes, the truck started up just fine after it died, it struggled to hold the idle around 400RMP's. I drove it back and once I reached my destination it slowly died again. I drove about 4 miles total, reaching 55-60mph.

We drove it back to the show the next day and pumped about 5 gallons of gas out of the bottom portion of the tank (I had topped it off earlier, and that's when all the problems started) to make sure there was no water in the gas. There was NO water but the gas looked yellow. The only additive I put in was Heat, I added it when I topped of my tank. We did not take off the new filter to check it, since we didn't get any sign of water or any other crap in the gas, other than it being fairly yellow.

Since there was no water in the tank, a friend of ours looked it up on YouTube trying to figure our what it could be. He decided to clean a portion of the fuel system. I can't remember what it is called. The actual part is located under the VORTEC cover of the engine. That part was really dirty. After we cleaned it and put it back on, the truck started up fine (like it did when we replaced the pump). The truck Idled a lot better holding 700RPM's. It doesn't struggle to hold the idle any more.

We didn't have time to check the pressure and I'll let you know what we come up with.

The check engine light did not come on after I initial started it, once we replaced the pump, nor has it come on since.

Thanks,
Rhonda
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
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There are a few things he may have cleaned. The idle air control valve could be an issue causing the low idle and stalling. Maybe that is what he cleaned. Also, he may have cleaned the throttle plate or a few other things.

Is the vehicle running properly now that he has cleaned something?
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
RMSPARKS1343
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The truck ran fine all day yesterday but when I drove it home and parked it, I noticed the check engine light was on. I make sure to check it after my friend cleaned a part of the fuel system and it wasn't on then. I'm not sure what the check engine light means, it was never on before.

Any thoughts?
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Thursday, February 18th, 2021 AT 12:51 PM
Tiny
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You need to scan the computer to see what trouble code is stored in the computer. Most parts stores will do it for free, so have that done and let me know what you find.
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Thursday, February 18th, 2021 AT 12:51 PM

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