General Maintenance & Repairs - missfire, but no DTC

So i have a 2000 chevy 5.3l, swapped into my 79 chevy 4x4.

runs about 50-60 psi depending on the vacuum of the engine.

I just recently started having a missfire, not bad enough to throw the check engine light on.

I was thinking it may be because i have a exhaust leak before the o2 sensor for some time now and it may have fouled a plug.
NOT THE CASE. i pulled both sides out and they all looked new still ( only month old AC delco's)
ONE DTC CODE I AM GETTING IS IDLE AIR CIRCUIT HIGHER THAN SET VALUE (or something along those lines)
Im not sure where else to go with this now, i even watched my o2 data..

what i am seeing is a b1s1 o2 is say +3.0% to 7%.. roughly.
while b2s1 o2 is say -.05% to -4% roughly.

i swapped a new o2 in the drivers side and it made no difference.

Does anyone else have any pointers on where to go about next? maybe a stuck injector? clogged? im not sure.

any ideas?

also i got a 2000 5.3l, and a drive by wire 04 6.0l i believe it is. can the 6.0l injectors be ran on the 5.3l
i did noticed my 5.3l injectors were 4 nozzles, compared to 6.0 with only 2 nozzles

If you are getting the IAC code, you may have a vacuum leak

i though the same thing. i ended up pulling injectors out and washing out the rails with fuel, put injectors back in, doesnt seem to have as bad of a missfire, but it still is way down on power. i can only think is that they are restricted

well i put another set of injectors in it today. a used set from a wrecking yard ( ya i know..)

but the problem is the exact same. each injector has power going to it ( tested with a noid light) but is it at the right time? idk...

this is strange how just one day it started to do this..
possibly a cam, crank, or knock sensor>

i really need help with this. anything is appreciated..

Thanks

Are you losing any fluids? How is the compression?

Are you losing any fluids? How is the compression?

does losing ATF count lol?

compression is good. i found out it was showing up on my computer that cylinder 3,4,5 all had some missfires. 3 and 4 were between 50 and 80..

i shut it off and cleared it. nothing came back for missfires.. although it was still missing.

pulled the injector wire on cylinder 3, made no difference, and same with 4

Sounds like bad coil packs

Sounds like bad coil packs

already swapped those

Did you test any of your sensors that you suspected?

Did you test any of your sensors that you suspected?

idk how to test a crank, or cam sensor..i could try one out of my brother 6.0l sitting in his garage

SO today i hooked up efi live, and found that cylinder 5 was missing the most..
check volts to the coil, and volts to the injector.. both had 14.. swapped plug wires and plugs.. and no difference...


any ideas?

Engine is stock?

Engine is stock?
yeah engine is stock

Do you possibly have a ground issue?

Do you possibly have a ground issue?

i wouldnt think so, but i was thinking the same thing. i need to check and see if there is a ground for injector 5, or coil pack 5, because those are my missfire problem.

i swapped a good cylinder coil to the bad cylinder and it didnt follow. and the injectors were done before that.

idk where else to go besides maybe a ECM

hopefully compression check tomorrow, maybe lift a valve cover. whats the compression psi suppose to be?

hopefully compression check tomorrow, maybe lift a valve cover. whats the compression psi suppose to be?

compression check, shot to 150psi almost soon as i turned the key over.

That sounds great, but at the same time, now what are your plans?

366137compression check, shot to 150psi almost soon as i turned the key over.