97 silverado L31 cylinder 3 issues p0303

[Dewman67]

Just my 2¢, I have a 97 k2500 l31. And have had similar problems and still do. Have checked compression, leak down, replaced dis, cap, rotor, and injector spider. Have had it check by ase mechanic, with no problems found. Which leads me to the junk black box computer. I still have bank 1 misfire, and bank 1 lean by looking at fuel trims. My belief is that it's not firing injectors right on bank 1. My plan is to do a 411 computer swap at some point.

 

[Unssafe]

Just my 2¢, I have a 97 k2500 l31. And have had similar problems and still do. Have checked compression, leak down, replaced dis, cap, rotor, and injector spider. Have had it check by ase mechanic, with no problems found. Which leads me to the junk black box computer. I still have bank 1 misfire, and bank 1 lean by looking at fuel trims. My belief is that it's not firing injectors right on bank 1. My plan is to do a 411 computer swap at some point.

hello,

i did a compression test on cylinders 1 and 3 and they both between 190 and 195, i remember i did a compression check about 9 months ago and they were all in that range then. i dont hear any noises from the valve train so i dont think it is that. also it was intermittent and got steadily worse until now it is doing it constantly.
my next step i think is get a scanner that can read injectors but i would be able to tell if they were good or bad. or make a appointment at the local chevy dealership and let them take a look, hopefully it will not cost alot.


or maybe find another 96 thru 98 extended cab z71.

 

[Supercharged111]

Just my 2¢, I have a 97 k2500 l31. And have had similar problems and still do. Have checked compression, leak down, replaced dis, cap, rotor, and injector spider. Have had it check by ase mechanic, with no problems found. Which leads me to the junk black box computer. I still have bank 1 misfire, and bank 1 lean by looking at fuel trims. My belief is that it's not firing injectors right on bank 1. My plan is to do a 411 computer swap at some point.

411 is more sensitive to misfire issues, so if it's not the PCM expect the problem to get worse. I too have been battling a misfire issue for years. I'm about to point the parts cannon at it because it makes no sense the way it acts.

 

[stutaeng]

hello,

i did a compression test on cylinders 1 and 3 and they both between 190 and 195, i remember i did a compression check about 9 months ago and they were all in that range then. i dont hear any noises from the valve train so i dont think it is that. also it was intermittent and got steadily worse until now it is doing it constantly.
my next step i think is get a scanner that can read injectors but i would be able to tell if they were good or bad. or make a appointment at the local chevy dealership and let them take a look, hopefully it will not cost alot.


or maybe find another 96 thru 98 extended cab z71.

You can check for injector pulse with a LED test light. At least that will tell you the injector is getting signal. Test light should blink. It's very easy to do. Just need a wiring diagram to figure out which wire to backprobe.

 

[Schurkey]

You can check for injector pulse with a LED test light. At least that will tell you the injector is getting signal. Test light should blink. It's very easy to do. Just need a wiring diagram to figure out which wire to backprobe.

Or use a ready-made "Noid light" of the correct sort to fit your harness connector.

 

[Supercharged111]

Can also use a timing gun

 

[Schurkey]

Can also use a timing gun

That's news to me. I wouldn't expect enough voltage in the injector wires for the inductive pickup to sense the injector pulse.

 

[Unssafe]

I just got off the phone the local dealership and they said it was a $130 diagnostic fee. So that is what I'm going to do.

Wish me luck[emoji846]

I will report back the results.

Thanks

Sent from my SM-N975U using Tapatalk

 

[mrvsfriend]

Very interested as well. I'm having the exact issues (254k mi) but P0301, cylinder 1 misfire. I have a brand new gm performance L31 engine, changed plugs, wires, cap, rotor, rotor gear, timing re-set, new coil, cleaned injectors and manifolds, swapped plugs and wires around (P0301 stays). Just started getting another code for o2 sensor in addition to the misfire. The misfire comes and goes... the black box hadnt even crossed my mind.

Looking forward to what the shop tells you.

 

[Supercharged111]

That's news to me. I wouldn't expect enough voltage in the injector wires for the inductive pickup to sense the injector pulse.

It worked on a Corolla I had eons ago.