Bad bad bad BAD misfire!

[SLCHOE]

At this point I would be looking at the control circuits of both the injectors and the Ignition coils. Do you know how to test the drivers for those inside the PCM? If you don't know and you do it wrong, you CAN KILL your PCM.

 

[oldsman003]

I do not know what that means. But the truck acted no different with the old pcm installed versus the new one

 

[SLCHOE]

I do not know what that means. But the truck acted no different with the old pcm installed versus the new one

The ECM has the drivers in it so we can rule that out but the control and ground circuits for both IGN and FI must be checked. This is very delicate testing with no room for error. Honestly, take the truck to a shop and pay the $100 to have it diagnosed. I talked about this in another thread about how shops charge $100 to diagnose engine drivability issues and sometimes it takes 20 minutes and sometimes 15 hours. Don't know how other shops work but if WE can't fix it it 99% of the time HAS TO go to the Dealer. Get the answer you are looking for and decide to either tackle it yourself if you can or have it fixed. You've spent way too much time and $$$ on this as far as I'm concerned.

 

[oldsman003]

I've paid the 100 bucks top 1 shop ands another 40 to a private guy and it got me no where farther

 

[oldsman003]

What should I be looking for wire wise in the harness? Burnt wires? The injector wires I've been told if there's a ground issue or had a ground issue can discolor the wires. The pink injector wires are slightly tanish where they used to be pink

 

[#1taho]

What should I be looking for wire wise in the harness? Burnt wires? The injector wires I've been told if there's a ground issue or had a ground issue can discolor the wires. The pink injector wires are slightly tanish where they used to be pink

when mine went I couldn't tell that it was bad. In the end it was loose pin conection's. I changed the harness and that head ach is gone. wish i could be more help, if that don't work I would start to look into a computer or have someone look at the tune in the computer to make sure it's working.

 

[oldsman003]

Fixed

 

[#1taho]

Fixed

That's great what was it ?

 

[oldsman003]

Well evidently everybody I've spoken to, ase mechanics gm mechanics being hooked up to 2 snap on tuners. And nobody told me there is a strategically hidden bank 2 precat. Completely blocked. Broke the flange loose on that side and fired her up and heard those four cylinders for the first time in months
Drove my truck with ease yesterday for the first time in 6 months. Felt great

 

[oldsman003]

Gave Bertha a good wash today to get 6 months of grime off of her, waiting on exhaust now, she sounds like a stock car with open manies!

 

[oldsman003]

Had to spend 3 hours yesterday buttoning up the wire harness from having it all apart train about frustrating!

 

[#1taho]

Congratulations on the find and repair. She looks like a real nice truck. I am sure you will be happy with it now. So over all what did it cost you ?

 

[oldsman003]

Well I have new crank, cam, maf, map sensors, throttle body, pcm, plugs wires coils head gaskets and timing set, upstream o2s and a whole bunch of time and frustration plus $100 in a shoo attempting to diagnose it

 

[SLCHOE]

Well evidently everybody I've spoken to, ase mechanics gm mechanics being hooked up to 2 snap on tuners. And nobody told me there is a strategically hidden bank 2 precat. Completely blocked. Broke the flange loose on that side and fired her up and heard those four cylinders for the first time in months
Drove my truck with ease yesterday for the first time in 6 months. Felt great

A whatnow? Where? Got a picture of it? Never heard of a precat or 3 cats on these trucks, CA or Federal emissions.

Let's say I've worked on these trucks as long as I have and for whatever reason or odds that I've never run into the elusive "bank 2 pre-cat". Why isn't there also a pre-cat on bank 1 and why was it not checked along with your other two long long ago? Something doesn't add up here.

Anyway glad you got it going again. Should have got it going again in post #4 and #6 of this 74 post thread though. LOL

 

[jough]

I'm glad you got it running. I have the mid-pipes (w/cats) off a 2004 Yukon Denali (LQ4) and there is only one cat on each side. Does the 2500 have two on the passenger side?
By the way, my passenger side cat is tripping the CEL for low efficiency. I am looking for another used one.

 

[oldsman003]

Yeah my truck has "4" cats two main and two previous cat converters. I will try and get a pic today and post. I'm not sure if it's because mine is a 2500 but from the manifolds it bumps to 3" pipe down to upstream o2s then precats then cats then muffler back. 2 true pipes back to the muffler, then on mine has some aftermarket muffler with duel exhaust.

 

[oldsman003]

Yeah well like I said nobody ever suspected it being a problem and as you stated never heard of these trucks having more than the main cats. When I saw the bank 1 precat I just figured it was a resonator for back pressure and to quiet the exhaust noise down, it is a yukon. Never crossed my mind

 

[oldsman003]

Here's 2 stock photos I finally found the straight 2 section is bank 2 the other is bank 1

 

[oldsman003]

Here's 2 stock photos I finally found the straight 2 section is bank 2 the other is bank 1

 

[SLCHOE]

OK so you have 4 cats. I was gonna say, I've never heard of a 5.3 with 2 cats on one side and one on the other.