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No starting properly

Tiny
SEAN0308
  • MEMBER
  • 1993 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 50,000 MILES
When I try to start it, it only cranks. I had to get a new battery the metal piece inside the battery looked like it was arching, and it was all chipped. I replaced the negative cable also. It still would not start so I had the alternator tested that was bad also. I replaced that and it still doesn’t start. If I hold my foot on the accelerator and start it, it fires off as long as I hold the accelerator down. Once I take my foot off the accelerator it shuts off. Any suggestion.
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Saturday, November 27th, 2021 AT 12:29 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,779 POSTS
Hi,

By pressing the throttle open, it shuts down the fuel injectors to clear a flooding issue. So, here is what I suggest. The first thing I want you to do is to check for diagnostic trouble codes. Here is a link that shows how it's done. You don't need a scanner. All that's needed is a short jumper wire or even a paper clip.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

I have a feeling the fuel pressure is high due to a faulty pressure regulator. This may have caused the plugs to fail. This is only a theory at this point, so let me know what codes you get.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Take care,

Joe
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Saturday, November 27th, 2021 AT 10:51 PM
Tiny
SEAN0308
  • MEMBER
  • 23 POSTS
Only code I was getting was 32 and I always get that. I have to change the EGR valve every 3 months. I pushed up on the plunger and it’s not sticking. I have old EGR might swap it today and see what happens.
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Sunday, November 28th, 2021 AT 9:18 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,779 POSTS
Hi,

By chance, do you know the model of transmission in the truck? It will either be a 4L60 or 4L80E? That makes a difference in the diagnostics potentially related to the problem.

Also, the EGR shouldn't go bad already. Have you removed it and inspected the air passageways in the intake? As far as the EGR, if you have a vacuum pump, see if the pintel moves when the vacuum is applied, and the valve holds pressure.

Let me know what you find.

Joe
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Sunday, November 28th, 2021 AT 6:13 PM
Tiny
SEAN0308
  • MEMBER
  • 23 POSTS
I took it to a mechanic, the spark plugs were black, the EGR valve was the same way. The timing was also off, and the fuel pump relay was bad. He did a compression test and said everything looked good. It runs better now but it is still running rich. He thinks the throttle body base is bad. He hooked a vacuum gauge up and when you accelerate the vacuum goes up I believe he said or down. Can’t remember. He said it wasn’t supposed to do that. Is it possible for the TBI base to be bad? I have only heard of the tops being bad either the fuel pressure regulator or the injectors. He recommended a new TBI for it. He set the timing changed the plugs and replaced the fuel pump relay. He also checked the fuel pressure and said that it was good also. I just had a new pump and tank installed.
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Wednesday, December 22nd, 2021 AT 1:53 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,779 POSTS
Hi,

It is completely normal for the vacuum to drop when you hit the throttle simply because you are opening up the throttle plate and allowing air to flow easier. So, I'm not really sure about that one. Also, the base plate gasket at the bottom of the TB would create a vacuum leak. As a result, the mixture would be lean and not rich. That could cause rough idle and stalling issues at idle.

Do me a favor. Follow the link below for testing for vacuum leaks. Do this where the throttle body is mounted. You will be using carburetor cleaner and spraying it toward the gasket. Do this with the air inlet tube connected to help prevent the fumes from being drawn in naturally through the throttle body.

If there is a leak, the engine RPMs will increase. If there is no leak, it won't change. Also, if you have the truck at home, try to pull codes after driving it for a little so we can see if there is anything new indicating a problem.

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

Let me know what you find.

Joe
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Wednesday, December 22nd, 2021 AT 5:16 PM
Tiny
SEAN0308
  • MEMBER
  • 23 POSTS
I sprayed it with carburetor cleaner no change in idle. Only code is 32 and I have replaced the EGR three times, and it throws same code 2 months after I replace it every time. Any chance the cat could be clogged, making it throw the 32 code. I can’t really tell if it is clogged because the exhaust fumes smell rich. I have smelled a sulfur smell but don’t know if it is. The other thing I was thinking it was maybe the MAP sensor. I have replaced the coolant temperature sensor and the IAC valve also. They pulled the EGR and said it was black from running lean and they had tested the EGR valve.
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Wednesday, December 22nd, 2021 AT 10:15 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,779 POSTS
Hi,

If the catalytic converter is plugged, it will affect the EGR airflow. However, there would be a noticeable power loss. I don't know if that's the case.

I attached diagnostic flow charts below. There are two different sets of diagnostics based on the transmission type.

IF you look at the last three pics, they explain how to identify the transmission type.

Let me know if you are comfortable doing this. Also, let me know if there is a power loss when driving.

Take care,

Joe

See pics below.
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Thursday, December 23rd, 2021 AT 9:44 PM

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