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Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4410
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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1993 chevy: oxygen sensor..fuel filter,compression is good..idling

Resolved Question:

1993 chevy silverado runs very rich i can smell fumes.Gas milage has dropped a lot,I replaced oxygen sensor, piugs and wires, knock sensor, fuel filter,compression is good. It misses sometimes when it is idling. The engine has 200k miles on it. The GM scope at the shop didnt show anything,do you have any other suggestions?
Submitted: 5 years ago.
Category: Chevy
Expert:  Jerry Newton replied 5 years ago.
Ignition timing is critical on these engines, and it is by far the most overlooked adjustment. Nobody checks the timing, or they check it improperly. There is a procedure on the label under the hood that tells you exactly how to check/adjust the timing, and the specification.

The next thing I would check is the MAP sensor vacuum hose, and the nipple on the throttle body that it attaches to. The nipple will actually plug up with carbon on the inside of the throttle body, and restrict the vacuum supply to the MAP sensor, which is a pretty important sensor in terms of fuel delivery.

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