Why is there a cylinder or possible 2 cylinders down?

Asked by Bryan Sep 19, 2022 at 06:11 AM about the 1989 GMC Sierra 1500 C1500 Standard Cab SB

Question type: Maintenance & Repair

Just did a complete tune up (gapped the plugs
myself) on my GMC Sierra 5.7 350 1/2 ton. Truck ran
great for 4-5 days. All of a sudden it's missing. Acts
like it's down a cylinder or 2. Ohmed the wires, they're
good. Cap and rotor button look fine. Been doing
mechanic work nearly 30 years now and I have never
had this problem before. Give me your opinions
please

3 Answers
307,265

Gene answered about a year ago

Compression test, both dry and wet, if all is good then has the distributor pickup and module ever been replaced?

Mark helpful
155,265

james answered about a year ago

Make sure one or more of the spark plug wires didn't fall on the hot exhaust manifold. When you do the compression test if you have 2 cylinders next to each other with very low or zero compression, you have a blown head gasket. A head gasket will sometimes blow in between two adjacent cylinders and not into the cooling jacket. Hope that helps! Jim

Mark helpful

Your Answer:

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