New-to-me ‘97 misses but throw no codes

[Aholter90]

Been a while since I’ve posted on this forum! My ‘96 K1500 is still running great as my daily, and I just picked up a ‘97 K2500 from a buddy to be my new tow pig.

The ‘97 is a 350 4l80e with 123k miles, and sat for about 2 years before I got it. I got it running in his driveway (poorly) but it ran enough I was able to limp it 45 miles home.

Over the past month I’ve redone the brake lines, replaced the starter, put on mirrors, swapped seats, and new plugs and wires. When I got it running at his place is missed consistently on 1 cylinder. I hoped as I replaced the plugs I could figure out which one but they were all pretty universally funky. With new plugs and wires it’s still doing the same thing. Engine throws no codes. What’s the next step, what should I investigate next?

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[DeCaff2007]

Check the distributor and ignition coil.

 

[stutaeng]

If the coil/distributor/wires are okay, then most likely the spider injectors. I'd take a look at those too.

 

[Ruff Idol]

If the coil/distributor/wires are okay, then most likely the spider injectors. I'd take a look at those too.

If not then afterwards I would run a comp test. Cyl 1 might be a little weak.

 

[Nad_Yvalhosert]

You're gonna want a scanner.
Pull up the datastream and check the misfire history. If cylinder 1 is consistently misfiring, pull out the spark plug and swap it with one that isnt misfiring. If the miss changes cylinders, the plug is the blame.
If not, swap plug wires.
If it's still misfiring then the problem is internal: injector spider, intake valve, compression, etc. as stated above.

Basically you should double check your work and rule out defective brand new parts before loading up the parts cannon on a teardown.

 

[boy&hisdogs]

You're gonna want a scanner.
Pull up the datastream and check the misfire history. If cylinder 1 is consistently misfiring, pull out the spark plug and swap it with one that isnt misfiring. If the miss changes cylinders, the plug is the blame.
If not, swap plug wires.
If it's still misfiring then the problem is internal: injector spider, intake valve, compression, etc. as stated above.

Basically you should double check your work and rule out defective brand new parts before loading up the parts cannon on a teardown.

You're going to want a GOOD scanner. My first few couldn't do this. I just recently got Torque Pro on my phone and a Bluetooth adapter for the OBDII port. It's $5 and you get access to all kinds of GM specific stuff and can put in custom PIDs if you don't see the thing you need listed by default.

It's still only 1 way and can't cycle the abs or anything higher level like that but it can read a lot more sensors than a cheapie "code reader" scanner.

I'm dealing with a similar issue with my 5.7. Two cylinders missing, only one throwing a code.

Here's a link to my thread about it if you want to see what I've been trying.

#2 Misfire at Idle, Random/Multi While Driving

98 K1500, 5.7/4l60e, 198k miles (It's the truck in my sig) Three times now over the past year or so my truck has given me P0302 (Misfire #2) at idle and low speed/rpms, like when I'm pulling out of the driveway. The first time it went away on it's own after a few days, before I could figure out...

www.gmt400.com

 

[Joe Dirte]

Fightin similar on my 98. 2 motors that miss on #5. When I get time I'm gonna check my main harness to see if maybe broke a wire.