Engine shaking/misfiring very low power when driving

WILLIAM MITCHELL2

MEMBER
2001 CHEVROLET BLAZER
4.3L
6 CYL
4WD
AUTOMATIC
145,000 MILES

I replaced everything that could be replaced as far as the fuel system goes and ignition system goes. New fuel pump, new fuel filter, new gas tank, new gas lines, new plugs an wires, new air filter, new injector spider, all new vacuum lines and hoses. And the engine is still misfiring. I'm just about fed up with it. I'm sure it's something simple. I'm just not seeing it the engine shakes worse than a blender and there is hardly an power when driving it.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

I can understand your frustration. Due to everything you have replaced we need to start looking at the engine sensors to see what the engine is telling us. Is it running rich/lean or does the ECM not even see a misfire. Each of these will point us in a different direction.

So we need to hook up a scan tool and look at two things. First, are there misfire codes or other codes? Second, we need to look at the o2 sensors when this is misfiring. What is the sensor voltage and what does the short term fuel trim say?

Depending on each of these we will know if there is too much fuel or not enough fuel. Then we will know what to go after.

Lastly, can you hook up a vacuum gauge to a vacuum line and see what the needle is doing. This will tell us if the intake valves are causing the issue.

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

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