99 tahoe misfire, win some,lose some

[ccapehartusarmyINF.(ret)]

a misfire history can answer several questions weather the missfires are more wide spread or isolated to one particular cylinder
becuase there has to be so many misfires on a cylinder in order for the PCM to register a misfire code there can be misses on other cylinders in the firing order but not enough to register a miss code or it could be isolated to just one cylinder there are a few directions to go in when diagnosing a missfire so a history cna help narrow that down a bit

 

[Kenny]

Ahh i see. That type of diag tool i dont have access to at the moment, though i may be able to borrow one to look at the counts.

 

[SunlitComet]

any scan tool that can read "gm data" in addition to the basic obd2 can show you that. that and ford and others are like a plug-in or extension of the existing scanner software. autoxray sells a few that can or better yet find an old snap-on mt250 series scanner that can tell devices on the engine what to do for diagnosis. add a fuel pressure tester and then you can even do injector balance test.

mine interacts with abs and srs system as well. will even show me tracked data on the tranny.

 

[Richamos1]

Check the pickup coil on the distributor those are notorious for the thin wire strands breaking.

 

[SunlitComet]

vortecs don't have pick up coils.

 

[BJ80]

I had a very similar issue with my 99 Suburban. It turned out to be a cracked head. The crack was next the exhaust valve on the 3rd cylinder. I was getting code P0303. Having the heads replaced now.

 

[DallasTahoe]

I did the same as you, bought from a young guy everything seemed to be fine, drove it for a week and now I have a miss. Replaced cap rotor wires coil and plugs, I was leaning towards injection spider, instead I did a compression test and found #4 and #6 cylinders have no compression, guess she blew a gasket lol


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