GMC Troubleshooting Questions? Ask a Mechanic for Answers
Hi, I am Mike, welcome. I'm reviewing your question.
Perhaps there is a worn down cam lobe on #7, check the cam lobe lift on each intake and exhaust valve and compare them to the cylinder next to it.
Then there must be a vacuum leak there at #7.
Did you check to make sure #7 fuel injector does have a pulse when cranking?
Yes. Intake manifold gasket.
Would you like the instructions for replacing the intake manifold gasket?
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