Have 99 silverado with a miss on two cylinders at any RPM,

Asked by Jul 20, 2014 at 12:40 PM about the 1999 Chevrolet Silverado 1500 3 Dr LS Extended Cab SB

Question type: Maintenance & Repair

Drove to work Friday morning with truck running great. When I left work Friday afternoon it
almost wouldn't run. Have spark on both cylinders, but don't know if it's at the right time.
No trouble codes other than "300". What else can I check.

4 Answers


I have a 99 silverado all so,had same issue,check your intake gasket,sound,s like it may be bad,if that is not the problem,check compression on the two cylinder,s that are missing.

already checked compression and it was fine. checked vacuum at master cylinder (only place I could find) and it seemed good also. no drop in vacuum when engine RPM went up. The cylinder it's missing on are 1 and 2. I loosened the plug wires and with engine running, remover wires one at a time. No difference in engine when 1 or 2 wires were pulled off. Just borrowed a NOID light to check PCM signal. Anything else I can check?


Was there fire at the 1 and 2?


Two things needed for ignition, fire and fuel. If you have spark, check the injectors or the module directing them. You may have congestion or crud. Check the fuel filters to see if there is any undesirables in them and or replace them anyway since you have them off. If you have spark when it is suppose to spark, and the plugs are good, I has to be the fuel. One and Two are on the opisite sides of the engine, so the two fuel rails are not the issue, but the injectors may be, or electronic malfunctions. Make sure the wires are secure to the plugs and injectors.

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