contribution test numbers

[seadoo48]

my truck has been having an issue for a little while now, if the truck is warm it always is pefect at cold the truck will shutter and run like sh**. i originally thought maybe it was ficm but could be wrong. i drove it cold to my buddies shop. as soon as we plugged it in to do contribution test cylinder 2 was slowly dropping to - 20 then to -40. by the time we noticed it truck zeroed out. all were at zero at idle. alot of them were dropping under throttle tho. any ideas? what should i be seeing for numbers.? do i need 8 injectors? thanks

[seadoo48]

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[6.0kansaspowerstroke]

im having the same problem

[sinner6.0L]

You're never going to have a flat contribution under throttle. usually only at idle or light throttle do the RPM drops really tell you anything.

You may catch a heavy dead misfire under throttle but that's about it. If you're not feeling the miss it's probably not there.

[seadoo48]

Im def feeling the miss just don't know what to do with the scan tool to see what is dropping out. I initialy was thinking ficm but starting to think injector

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[sinner6.0L]

what kind of scan tool were you using?

[naraptor]

This is what I do: I let the truck sit over night, the plug in the scan tool( snap-on) then set up the contribution test, then start the truck and which every cylinder or cylinders can't 0 out those are the ones. But torn high presure o-rings can cause funky problems.

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[seadoo48]

I want to say snap on motus ? it was showing numbers with truck running. All were zero at idle for most part. One was bouncing around for about a minute. By then truck was almost warmed up

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[ZMANN]

sounds like stiction and even the dealer couldn't figure mine out with a scan until a second injector had an issue


I don't see how you could drive it cold to the scan location and get a good test ?

like mentioned they need to really be cold

[seadoo48]

Did a cold contribution test today. Cylinder 4 was pretty much dead till warm. Others were all over the place too till warmed up? think i need an injector and ficm?

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