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I took my truck (2006 chevy silverado 5.3l v8) to chevrolet dealership due to the fact that it kept sputtering then dying. The check engine light was on the whole 9 yards.

The fuel pump has been replaced; the MAFs replaced, new air filter, new knock sensors, the O2 sensors tested good, new spark plugs, oil change, CATs were tested and came back good. I was out of options, so I took it to Chevrolet and they had it for 2 days saying they've never seen this before.

They finally called me and said my spark plugs on the driver side fouled out. I asked why, given that they were brand new? They said they didn't know, but it's fixed. Lo and behold, that evening it started sputtering again; it died again next day on the way to work while driving 60 down the road.

Monday morning the truck had to be pulled back to the chevy place. They called me next day and said I owe them more money as it had a wire ripped out of the wiring harness. I refused: they should've fixed it the first time and they had it last working on it. If a wire was ripped out, they should have seen that. As I said that, their whole demeanor changed and they claimed that this is now a whole different problem; the first one was due to an O2 sensor that caused my brand new plugs on the driver side only to foul out, but can't have caused the ground wire they found this time.

I don't believe them. I don't believe an O2 sensor being loose the first time caused it; I think it was this ground wire they found this time. They just want me to pay more money because they didn't bother to even look the first time.

What do you reckon?

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You say that the O2 sensors tested good. How were they tested? – Zaid Jul 9 '14 at 20:11

A loose O2 sensor will give a weak signal to its ECU. The ECU will then richen the mixture on that bank, possibly accounting for the plug soiling. If the vehicle is then road tested before release the subsequent faulty wiring would normally be found. Without being hands on with this particular vehicle it would be impossible to be definite about its faults or if to blame anyone. What I would say though is that if a vehicle has persistant and repetitive faults then one good way to get to bottom of things would be to run the vehicle with a data logger connected. This will give you a second by second view of any fault developing and go a long way to nailing it whilst sitting at your computer.

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IMHO, O2 sensor can't cause damage. If signal is faulty - ECU must be working in safe mode. That is why your check engine lamp was light on.

But if you have bad high voltage wires (plugs - coil) then high voltage jumps through any weak points and can damage and even solder parts. It also can damage ECU and its electronic parts like condensers. I suggest you to change wires every 0.5-1 year, it is cheap but very important.

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changing wires every year? isn't that a bit much? – chilljeet Feb 14 '15 at 8:38
Just try and see difference – Denis Efimov Feb 14 '15 at 8:40
In many cars I have never changed the plug leads, this is completely excessive. Also, many modern cars use COP (coil on plug) where only low voltages run in the wires, making changing them, unless damaged, redundant. Definitely every year is complete overkill unless you run some sort of boosted voltage that can strike through. – Elias Apr 15 '15 at 14:38

If you are getting an O2 sensor code, you really need to start at the core of the motor, and have your intake, exhaust, and head gaskets redone. O2 sensors throw codes if there is an air leak, and it could be far from the O2 sensor. A valve adjustment may also be necessary. If it's dying while you're driving down the road, that sounds like your alternator. Also if you are jumping on the highway without letting your car warm up, your spark plugs can actually shatter.

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I'm just wondering why you would start doing checks away from the O2 sensor for an O2 sensor issue? You should start at the O2 sensor and go from there. What you are suggesting is fixing things which don't need fixed first, then getting back around to the O2 sensor in the process. No way to diagnose ANY issue. – Pᴀᴜʟsᴛᴇʀ2 Jan 24 '15 at 18:01
Well most people would think that but, that's like replacing a light bulb every time your power goes out actually. – GettingNifty Jan 24 '15 at 21:15
And most people would be right. I didn't say replace the O2, I said to start your diagnosis there. You are willing to rebuild an engine to fix an O2 problem, which is bass-ackwards. – Pᴀᴜʟsᴛᴇʀ2 Jan 24 '15 at 22:39

When an O2 sensor goes bad the ecu knows it and ignors it so only enextended driving period may cause the plugs to foul but certainley not in the short run . While on the other hand your injectors get + all the time from a common wire and the injections come from - that pulsates from the ecu each injector with its own wire . If these wires are shorted together or to ground (-) the injector (s) may be continuously open causing large amounts of fuel to flow into the affected cylenders and cause one side of the motor to foul while the other side works fine

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