99 yukon 5.7 vortec misfire HELP

[lifted_yukon22]

Ok I'm going try to get a compression tester sunday

 

[lifted_yukon22]

Sorry for the time it took me but I been busy this week. I was only able to do cylinders 3,5 and 7 before it started raining. #3 was 172 psi. #5 170 psi, and 7 182 psi.

 

[SunlitComet]

safe to say in that case that you should consider it a fuel or spark delivery issue.

 

[lifted_yukon22]

What would you replace/check next?

 

[SunlitComet]

do you have an active spark when using a spark tester on number #5? Or what ever one had the high misfire number?

 

[lifted_yukon22]

I may sound like a idiot but what's active spark? If you mean it's sparking while you are grounding out that wire then yes

---------- Post added at 04:55 PM ---------- Previous post was at 04:50 PM ----------

Oh ok I gotta spark tester....if it runs fine while idling wouldn't it show spark being ok?

 

[SunlitComet]

yes. the next step in a shop would be to do an injector balance test. this would show if an injector is not functioning correctly. incidentally it also tests the injector circuits in the pcm as well. the proper scanner along with a pressure gauge shows the pressure drop-off the whole system after firing a specific injector several times. you compare the pressures after the firing to find if one is clogged up or leaking.

 

[ccapehartusarmyINF.(ret)]

Sorry for the time it took me but I been busy this week. I was only able to do cylinders 3,5 and 7 before it started raining. #3 was 172 psi. #5 170 psi, and 7 182 psi.

hey man you dodged a bullet there looks like all those misfiring cylinders are getting good compression
like he said its safe to say its a fuel or spark delivery issue

 

[lifted_yukon22]

Ok when I get time I will hook my fuel pressure gauge up and purge each injector and watch the drop and see of there's any difference between them. One of my friends is using my fuel gauge so bare with me.

---------- Post added at 07:41 PM ---------- Previous post was at 06:58 PM ----------

Ok when I balance the injectors I do it with engine off and cycling the key between balancing to get pressure back up am I right or am I way off?

 

[lifted_yukon22]

Ok sorry it took me so long....after each before balancing the injector thr starting pressure was 58 after energizing the system..
#1 - 45 psi
#2 - 46 psi
#3 - 48 psi
#4 - 46 psi
#5 - 46 psi
#6 - 45 psi
#7 - 46 psi
#8 - 46 psi

---------- Post added at 05:38 PM ---------- Previous post was at 05:28 PM ----------

Before each balancing* my mind was wondering lol