Random misfire at idle 454 vortec

[elevatorman]

Quick question ive just realized my pre 02 sensors bank 1 is a 5 wire bank 2 is 4. Which is correct it is a 97

 

[Schurkey]

WHAT VEHICLE?? WHAT ENGINE??

A 5-wire O2 sensor is news to me.

If it plugs into the vehicle harness...I guess it's correct.

 

[454cid]

WHAT VEHICLE?? WHAT ENGINE??

A 5-wire O2 sensor is news to me.

If it plugs into the vehicle harness...I guess it's correct.

97 k3500 454 vortec.... this is actually the OP asking the question rather than a newbie digging up an old post and asking.

I just looked at Rockauto, and also remembering what I had/have for my 99, the sensors are the same left to right (Bank 1&2) but are different upstream and downstream. I do not see any 5 pin connectors. One is a flat four, and the other a square 4.

 

[elevatorman]

97 k3500 454 vortec.... this is actually the OP asking the question rather than a newbie digging up an old post and asking.

I just looked at Rockauto, and also remembering what I had/have for my 99, the sensors are the same left to right (Bank 1&2) but are different upstream and downstream. I do not see any 5 pin connectors. One is a flat four, and the other a square 4.

It is technically 4 wire harness but has a 5th wire grounding the body of the 02.
Some new things have been discovered if i unplug the map trucks runs damn near perfect obviously its staying closed loop but even before it missed then. It will never misfire with the map unplugged.
The map is working correctly and reading roughly 1.8v at idle and my vacuum gauge is showing a steady 15inhg at idle.
I replaced my fpr again with a known good part number that should produce 58-62 psi but still im low only pulling 49 running 55 at prime.
I have not gotten around to doing a leakdown test again havent had any help and its just aggravating by myself with this truck. Fuel trims seem too hold slight negative for now

 

[Schurkey]

97 k3500 454 vortec.

OK.

also remembering what I had/have for my 99, the sensors are the same left to right (Bank 1&2) but are different upstream and downstream. I do not see any 5 pin connectors. One is a flat four, and the other a square 4.

That's the way I remember my '97 K2500 7.4L

It is technically 4 wire harness but has a 5th wire grounding the body of the 02.

I can't argue that...but it's not what I remember. Been several years, so maybe my memory is faulty.

If one upstream sensor has that 5th wire, and the other upstream doesn't...I'm wondering if someone added that wire for reasons of their own.

Photos? In-focus, nicely-cropped, please.

Some new things have been discovered if i unplug the map trucks runs damn near perfect obviously its staying closed loop but even before it missed then. It will never misfire with the map unplugged.

MAP? Not the MAF? I'd have expected the MAP unplugged would make it run really horrible.

I replaced my fpr again with a known good part number that should produce 58-62 psi but still im low only pulling 49 running 55 at prime.

1. RUNNING is going to be lower pressure than priming pressure. 50 PSI running wouldn't scare me too much.
2. How accurate is your gauge? Being a couple PSI off is not a huge concern, but you'd need to allow for that when diagnosing a problem.

 

[elevatorman]

MAP? Not the MAF? I'd have expected the MAP unplugged would make it run really horrible.

Definitely the map which explains the resistors i found weeks back

 

[elevatorman]

OK.

That's the way I remember my '97 K2500 7.4L


I can't argue that...but it's not what I remember. Been several years, so maybe my memory is faulty.

If one upstream sensor has that 5th wire, and the other upstream doesn't...I'm wondering if someone added that wire for reasons of their own.

Photos? In-focus, nicely-cropped, please.


MAP? Not the MAF? I'd have expected the MAP unplugged would make it run really horrible.


1. RUNNING is going to be lower pressure than priming pressure. 50 PSI running wouldn't scare me too much.
2. How accurate is your gauge? Being a couple PSI off is not a huge concern, but you'd need to allow for that when diagnosing a problem.

I will try and hook it up to my air compressor see what i get assuming the gauge is correct on compressor