#5 misfire

[Joe Dirte]

Posted in the what did you do today thread but figured to get technical it should go here. My friend Andre the Giant brought down snap-on Solus legend scanner. Hooked it to my 98. Haven't had a check engine light but it has been running rough. Same issue as before, ~1700 rpm engine shakes like a dead hole. Get it above 1800rpm n it's smooth. Previous motor did the same thing. Ran the live data n the misfire counts on #5 were thru the roof. I have spark (last I checked) so I'm guessing fuel. I have the updated spider also. Now his Solus couldn't read injector pulse and neither can my torque app. Other friends Solus was reading pulse on the Escalade when he was chasin down cam sensor issue. He runs a business Workin alone so his time is limited for doin favors. Before I fire the parts cannon and buy a new injector for #5, what are some other ways to test the injector itself without tearing it apart. Would a noid light work? Never used one. I've used a 12v test light before on my 4.3 to check for bad injector but that was 4 yrs or so ago n can't remember how I went about that. Theoretically if I do need to get into intake could I swap #5 to another cylinder and see if the misfire moves with it? Will be double checking all spark again tmrw after work just to be sure. Hell my luck it's somethin stupid like a bad wire or the plug on injector came loose. Thanks.

 

[Erik the Awful]

A noid light is the easiest way. Plug it in. If it lights, the injector should be injecting. Double-check that spark before you go replacing injectors, though.

 

[stutaeng]

I use a led test light for injector pulsing checking. I was at O'Reilly's just a few days ago and saw that they had a noid light kit on the rental list.

That scanner should be able to do injector balance test. That's what I would do personally to see if there's an issue with the injector itself. You can also check the impedance on the injectors. Compare the offending one to a good one.

Unless you have some weird issue with the electrical signal not being good (will need a lab scope for that,) it's most likely one of the two issues.

Yes on swapping the injectors. Costs nothing but will require some work. I'd take the easiest way to check before tearing into it.

 

[Joe Dirte]

I use a led test light for injector pulsing checking. I was at O'Reilly's just a few days ago and saw that they had a noid light kit on the rental list.

That scanner should be able to do injector balance test. That's what I would do personally to see if there's an issue with the injector itself. You can also check the impedance on the injectors. Compare the offending one to a good one.

Unless you have some weird issue with the electrical signal not being good (will need a lab scope for that,) it's most likely one of the two issues.

Yes on swapping the injectors. Costs nothing but will require some work. I'd take the easiest way to check before tearing into it.

Do you remember how to do it with a test light? I'm gonna start with double checkin spark first then slowly work toward the more difficult to hopefully find an easy or maybe stupid fix that I may have missed.

 

[stutaeng]

Do you remember how to do it with a test light? I'm gonna start with double checkin spark first then slowly work toward the more difficult to hopefully find an easy or maybe stupid fix that I may have missed.

Just trace the wires on that big injector connector and backprobe the pins and hook up your test light. You need a wiring diagram.

 

[Joe Dirte]

Just trace the wires on that big injector connector and backprobe the pins and hook up your test light. You need a wiring diagram.

I think I have the diagram somewhere. Hopefully this is only 8 n the gate today n I may piss with it tonite. Not feeling a 12r. Goin on 2 hrs sleep.