Misfire with no CEL?

[slowride]

Took my 04 Suburban out on the road today to check out my new brake job and hooked up my scanner to try it out to see what real time info it gives. I had it set on the screen showing cylinder misfires and all cylinders were showing 0, but then cylinders 1, 5, 6, and 8 started showing misfires with the readings going from 0 to like 2 or 5 then back to 0 and then randomly repeating that with varying misfire counts. This was while cruising at around 60 and I couldnt feel anything happening like running rough or hesitating and the CEL never came on. When I scrolled to the misfire history screen, there were some high counts on those same cylinders, 197 on cylinder 6 and 210 on cylinder 5 for example.
Anybody have something like this happen before? Thinking about pulling those plugs to check them. Is there anything in particular to check out that might be causing this? Thanks

 

[swathdiver]

Well, for starters, what kind of fuel are you running? If it is not top tier 91-93 octane then run a couple of tanks of it and check again. Check your plugs and wires and if your tool is able, test your injectors, check your oil and coolant,etc.

 

[rockola1971]

Well, for starters, what kind of fuel are you running? If it is not top tier 91-93 octane then run a couple of tanks of it and check again. Check your plugs and wires and if your tool is able, test your injectors, check your oil and coolant,etc.

Why would he need to run 91-93 octane gas in a engine DESIGNED for 87 octane? [Raising the BS flag] Check the oil and coolant, for a engine misfire condition? WTF? You been drinking tonight?

 

[swathdiver]

Because they run like crap on 87???

 

[treehan77]

No. Runs fine on 87

 

[slowride]

Im planning on changing the fuel filter on it this weekend too. If it was a problem with the fuel itself, I would think it would have shown misfires across all the cylinders not just 4 of them?

 

[Chubbs]

Unmetered air for starters. compromised vacuum tubing, intake manifold gasket seems to be coming up more frequently.

 

[rockola1971]

Because they run like crap on 87???

Well thats odd as hell. Both my 2003 Tahoe 5.3L run just fine on 87 octane and so does my 05 Yukon Denali 6.0L and thats all I put in them. So I guess I scored the rare unicorns from GM...On the used market. {raising the BS flag}

If you or anyone elses doesnt run right it aint because its got 87 octane in the tank Unless there is a 1/4 inch of carbon sitting on top of all the pistons.