Runs rough and starts to backfire after it has warmed up

TRAVIS1989

MEMBER
1989 CHEVROLET SILVERADO
5.7L
V8
4WD
AUTOMATIC
115,000 MILES

Motor starting cutting out while driving down the road, I replaced sending unit, new plug wires, replaced the whole distributor and timed the engine. Sometimes it runs fine but noticeable lack of power while driving down the road, and sometimes it starts backfiring almost like it is flooding out and wants to stall out while driving. I get code 42? I do not know where to start with my problem.

9 Replies

JACOBANDNICKOLAS

MECHANIC
108,489 POSTS

Hi and thanks for using 2CarPros.

The code, 42?, could that be a P0420? If that is the code, suspect the catalytic converter is plugging causing a backfire, loss of power and rough running conditions.

Here are two links. The first discusses symptoms of a bad converter. The second explains how to test one.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Check this first. If the code is a P0420, that is a catalyst code.

Let me know what you find.

Joe

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Saturday, November 24th, 2018 AT 5:42 PM

TRAVIS1989

MEMBER
16 POSTS

My truck has no catalytic converter, it was cut off at the "y" pipe right under the cab when I got it so I finished the exhaust. Today I started going through my wiring harness and found a few bare wires like one of the injectors and a red wire the under-hood light and cleaned the grounds on top of the motor. I brought number one piston to TDC and re-dropped the distributor and timed it with a light. Also I put new plugs in it and have not had any codes come up yet just driving around town. I will do that tomorrow and get back to you with the results.

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Saturday, November 24th, 2018 AT 7:17 PM

JACOBANDNICKOLAS

MECHANIC
108,489 POSTS

Welcome back,

Let me know. The bare wire on an injector can be an issue. By the way, if you find out for sure what the code is, let me know.

Take care,
Joe

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Saturday, November 24th, 2018 AT 7:50 PM

TRAVIS1989

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16 POSTS

I drove for it fifty miles down the highway and no codes came up.

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Monday, November 26th, 2018 AT 7:10 AM

JACOBANDNICKOLAS

MECHANIC
108,489 POSTS

Welcome back:

Is the vehicle now running correctly after the wiring repairs (specifically the injector wiring)?

Let me know.

Joe

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Monday, November 26th, 2018 AT 12:17 PM

TRAVIS1989

MEMBER
16 POSTS

Yes it is.

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Tuesday, November 27th, 2018 AT 12:32 PM

JACOBANDNICKOLAS

MECHANIC
108,489 POSTS

Excellent! I am glad to hear you got it fixed.

Let us know if you have questions in the future.

Take care,
Joe

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Tuesday, November 27th, 2018 AT 6:48 PM

TRAVIS1989

MEMBER
16 POSTS

So I drove the truck about two hundred miles now and just had two codes come up on my drive home. The first is code 32 that is for the EGR valve, I replaced the vacuum lines to the EGR solenoid and I have replaced the EGR solenoid itself and changed the EGR valve also with one off of a truck I know that works. I have had this problem off and on for quite a while and do not know what else to do with it. The second code is 45 which means rich exhaust. I am starting to suspect my o2 might be bad but I replaced a couple years ago and have only put about 10,000 miles on it in the last couple years. Can you help me out?

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Friday, November 30th, 2018 AT 5:56 PM

JACOBANDNICKOLAS

MECHANIC
108,489 POSTS

When you replaced the EGR, was the intake clean inside? Also, reconfirm fuel pressure. If the regulator has failed, pressure will go up and cause a rich mixture.

Let me know.
Joe

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Friday, November 30th, 2018 AT 8:26 PM