Cylinders 3 and 4 misfire?

2002 GMC SONOMA

156,000 MILES • 4.3L • V6 • 4WD • AUTOMATIC

CLI3200

MEMBER
2 POSTS

My truck listed above runs and drives fine with the misfire codes it’s throwing, but you can tell at idle it definitely has a miss. has new plugs, wires, injectors, rotor, and cap points cleaned, new MAF and it still has cylinders 3 and 4 misfire. There is no gas or coolant in the oil, not burning any coolant and no oil in coolant. I'm kind of at a loss and don’t know what to do next.

May 1, 2023 at 12:46 AM

STRAILER

✓Experienced Mechanic
55,224 POSTS

These engines had a problem with the spider injector inside the intake manifold. But we should do a compression test to make sure the engine is okay.

This guide can help:

https://www.2carpros.com/articles/how-to-test-engine-compression

And this guide can help as well:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Here is how to change the injectors out in case you need them in the images below. I would use an OEM unit. Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.

Images (Click to enlarge)

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May 1, 2023 at 4:08 AM