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My engine stalls at idle why?

Tiny
4DRTOM
  • MECHANIC
  • 467 POSTS
Hello,

I just went through this thread. Yes, it seems to me that something involved with the converter repair has caused this. Sound like it was a bit a a hassle if you broke 2 studs you must have been up in and around the whole engine compartment. You either accidentally hit something or didn't hook something back up. A ground wire somewhere would be common for this. Maybe one going from the engine to the frame or the engine to the transmission or transmission to the frame. The grounds that run under there get highly weathered and easily broken off. If I may ask what was the situation that made you change out the torque convertor?
Tom
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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I changed it because the converter lockup wasn’t working and the converter wouldn’t build pressure very fast so if you let off the throttle while cruising once you got back to the gas it would rev up like slipping before it grabbed but it was the TC not actual transmission slipping. This issue was fixed after the new converter but then came my new problem and so far I can’t figure it out?

Also after the install I noticed a broken ground strap but couldn’t see where it came from I assumed it was an engine to frame (because the firewall to frame was still good) so that’s where I hooked it up, is it possible that ground should go to a bell housing bolt instead? Would it make a difference?

As far as I know every plug is plugged in, no vacuum lines damaged or unhooked no broken wires anywhere I can find. Any help you may have is appreciated, thank you.
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
JACOBANDNICKOLAS
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Hi,

An exhaust leak before the O2 sensor can allow unmetered air to enter the exhaust. As a result, the sensors tell the computer the mixture is too lean. Then, the computer compensates by making the fuel mixture richer. It could be too rich. If you have a live data scan tool, check the short term fuel trims and let me know what they are.

Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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No, I don’t have a live data scanner. I’ll fix my leaks because it needs to be done anyways, and then see if it changes anything.
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Hi,

I hope that helps. Are the leaks before the oxygen sensors? I'm questioning it from past experience. I can't guarantee that is the cause, but it's possible. Ford V8's are known for it.

Let me know if you need anything or have other questions.

Take care,
Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Yes, the leaks are before. There is only one oxygen sensor if I’m correct and it’s at the Y pipe underneath the passenger door. I’ll be sure to let you know if I have any other questions, thanks for your help!
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Hi,

There should be two. One should be in the left side rear area of the exhaust manifold. The other is in the exhaust under the truck.

See attached pic.

Let me know.
Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Okay, thank you!
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Hi,

You are very welcome. Let me know if you have other questions or need help.

Take care,
Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Hey there, I fixed my exhaust leaks and the problem still persists. You have any other ideas? Haha! Thanks
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
JACOBANDNICKOLAS
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Hi,

I read back through all our posts. When you checked for a vacuum leak, was it only a visual inspection or did you use something like carburetor cleaner to check?

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

When it does stall, does it happen quickly or does it slowly stall?

Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Only visual and feeling with my hands/listening I was nervous to spray something to test, I was scared of it catching on fire. Also it just shuts off almost like turning the key off unless I give it some gas pedal right as soon as I can hear it shut off then it will barely stay running for maybe like 3 seconds then levels out and runs fine.
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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I understand your concerns. Your description sounds like it is more related to a fuel supply issue than it does electrical. In most cases, an electrical component just shuts down regardless if you hit the throttle. Have you confirmed fuel pressure? Heck, it could even be too high.

Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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No, I haven’t tested fuel pressure yet. Just another test I’ll have get around to doing!
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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The idea that you are able to keep it running is making me think it could be related. I still question a vacuum related issue as well. If you have a vacuum gauge, connected it to a port on the intake and start the engine. It should read between 18 and 20 inches. Try that and let me know what you find.

Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Sounds good! Will do.
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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Hi,

This post has resurfaced under new. I was wondering if you had any luck finding the issue.

Let me know.
Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
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No, I haven’t done any further test yet, just haven’t had much time at the moment. Hopefully I can get to it soon and check again for vacuum leaks and fuel pressure. Thanks
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
JACOBANDNICKOLAS
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Hi,

Not a problem. Whenever you get to it, let me know. I was just curious why it listed as a new post. It confused me.

Take care of yourself,

Joe
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)
Tiny
JGEASLEY
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  • 1991 CHEVROLET SILVERADO
  • V8
  • 4WD
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  • 235,000 MILES
I have replaced the throttle position sensor and the idle air control valve both to no avail. When idling the truck will idle real low and most of the time die. Just tonight after replacing the IAC valve it wants to die even if it is moving if you are not accelerating.
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Thursday, February 18th, 2021 AT 1:01 PM (Merged)

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