6.0 astro van Chasing unknown misfire and 02 sensor issues. Please help

[swsmotorsports]

Hey guys, this is my first post. I've used the resources here for a few years, though.

Im having hell keeping my LS swap happy and chasing unknown issues, particularly with an intermittent cylinder 2 misfires. But while logging that, I found my o2 sensors stop switching voltage. i haven't done much tuning as tuning with a misfire is a pointless endeavor.

the setup.

6.0, TBSS intake, 92mm throttle body, ported 799 heads, BTR Truck Noris cam, 10.6:1 Cr, stock exhaust manifolds, dual 2.5" exhaust to a single 3.5" (free-flowing muffler), 25-2700 rpm stall Jakes performance stage 4l80e in an AWD Astro van.

I plan on boosting it in the future, but I want all the issues ironed out before then.

I have an AEM 30-0334 that refuses to show up in VCM scanner as well, but that's a secondary issue. i have 2 pcm's and 2 2 logs70Lb_van_pcm.hpt newinjectors.hpl


at 5:34 I do a small pull, and afterward, the O2 sensors stop switching voltage, and the cylinder 2 misfire comes back.
please help. if there are any channels that I'm not logging that need to be, please tell me.

The other PCM is and log shows the O2's stop switching as well. (but this time no misfire)otherpcmDrive1.hpl black_70lb.hpt

[blindsquirrel]

A misfire sends unburned oxygen and unburned fuel out the pipe, and oxygen sensors detect oxygen - not fuel. So a misfire is picked up as a lean condition. The misfire is making the PCM change from CL-Normal to OL-Fault, and in open loop it's no longer targeting Stoich and making the O2s switch like they do in closed loop. Track down the misfire, that's what is causing all the other symptoms.

[blindsquirrel]

AEM-0334 is CANbus-only, it will not get picked up on a pre-Gen4 comms system. You need to use the analog output from the WB.

[swsmotorsports]

That kind of sucks, i was under the impression that the obd2 interface acted as a separate "PCM" In vcm scanner, and as such, was functional regardless of what pcm it is connected to. Any easy solutions you know of?

also, I have been trying to track down the misfire, but I can't seem to do so. it runs just fine, then suddenly changes. I'm wondering if I missed something in the calibration
New coil, wires, plugs, and coil sub-harness

Thank you for the reply

[blindsquirrel]

Any easy solutions you know of?

You need to use the analog output from the WB.

[blindsquirrel]

https://forum.hptuners.com/showthrea...les-Any-takers

[swsmotorsports]

https://forum.hptuners.com/showthrea...les-Any-takers

im runing the MPVI2, no pro Link. so, that doesn't help unfortunately.

[TheMechanic]

im runing the MPVI2, no pro Link. so, that doesn't help unfortunately.

Fortunately you can upgrade to pro for a very reasonable amount and have analog and CAN in the same wideband. I use it on everything and only have to have one wideband.

[blindsquirrel]

I dunno if anybody mentioned this yet, but you can just use the analog output from the -0334 and log it that way.

On the other hand, I guess you could use the analog output wired to an unused, or temporarily unused, 3-wire 0-5v engine sensor.

You could also use the analog output and connect it to the A/C pressure sensor, and then log that voltage in the scanner and do the transform whatchamadoodle thing and turn it into an AFR or EQ ratio.

Or, last resort, you could use the analog output and...

[swsmotorsports]

Fortunately you can upgrade to pro for a very reasonable amount and have analog and CAN in the same wideband. I use it on everything and only have to have one wideband.

the cost to upgrade is $250. and logging the WB is not the concern of this thread.

I looked at the log again, and it seems when in closed loop is when it misfires. now, im not sure if the misfire is causing closed loop, or if closed loop is causing the misfire. but when I can drive for 30 min at a time without a misfire, it tells me its an issue with the tune, not a hardware issue.

[blindsquirrel]

What part of the tune can make only one cylinder misfire? Show me the table.

[blindsquirrel]

When it's misfiring, is there spark at the plug? Spark in the cylinder? Signal to the coil making it all the way from PCM thru the harness to the coil? Still has good +12v and GND while misfiring?

Are you sure it's spark and not an injector/injector control problem? Constant +12v to all injectors? Is #2 injector still getting signal on the control side when it misfires? Is the injector going open circuit, or locking closed, or hanging open, when it gets hot?

[swsmotorsports]

12v to all injectors, noid light also confirms injector 2 is receiving the signal.
when injector 2 is unpluged or disabled in VCM scanner, the misfire is noticeably worse.

Wiring to the coils has been checked
new coil and coil pack sub-harness
Grounds are all shared

unfortunately, I cannot test the circuit with the engine actively running

[TheMechanic]

12v to all injectors, noid light also confirms injector 2 is receiving the signal.
when injector 2 is unpluged or disabled in VCM scanner, the misfire is noticeably worse.

Wiring to the coils has been checked
new coil and coil pack sub-harness
Grounds are all shared

unfortunately, I cannot test the circuit with the engine actively running

So you haven't heard of an oscilloscope?

[swsmotorsports]

So you haven't heard of an oscilloscope?

I am familiar with them. I do not own one

[TheMechanic]

You should take it to someone that does. It will save you a sh*t ton of wasted time and effort chasing your tail. Try to find someone over 45-50 years old. They will know how to diagnose a pattern better than the youngsters.

[gtstorey]

You should take it to someone that does. It will save you a sh*t ton of wasted time and effort chasing your tail. Try to find someone over 45-50 years old. They will know how to diagnose a pattern better than the youngsters.

I'm 2 for 3. I just bought an Autel Scanner with oscilloscope. I'm over 50years old. Now for the 3rd part, I still need to learn to use it.

[TheMechanic]

I'm 2 for 3. I just bought an Autel Scanner with oscilloscope. I'm over 50years old. Now for the 3rd part, I still need to learn to use it.

Just check out the sample patterns as I believe that is a Hantek "O" scope. Lot's of info out there on how to analyze the data.

[Alvin]

Hey guys, this is my first post. I've used the resources here for a few years, though.

Im having hell keeping my LS swap happy and chasing unknown issues, particularly with an intermittent cylinder 2 misfires. But while logging that, I found my o2 sensors stop switching voltage. i haven't done much tuning as tuning with a misfire is a pointless endeavor.

the setup.

6.0, TBSS intake, 92mm throttle body, ported 799 heads, BTR Truck Noris cam, 10.6:1 Cr, stock exhaust manifolds, dual 2.5" exhaust to a single 3.5" (free-flowing muffler), 25-2700 rpm stall Jakes performance stage 4l80e in an AWD Astro van.

I plan on boosting it in the future, but I want all the issues ironed out before then.

I have an AEM 30-0334 that refuses to show up in VCM scanner as well, but that's a secondary issue. i have 2 pcm's and 2 2 logs70Lb_van_pcm.hpt newinjectors.hpl


at 5:34 I do a small pull, and afterward, the O2 sensors stop switching voltage, and the cylinder 2 misfire comes back.
please help. if there are any channels that I'm not logging that need to be, please tell me.

The other PCM is and log shows the O2's stop switching as well. (but this time no misfire)otherpcmDrive1.hpl black_70lb.hpt

There's no chance that you have the rear o2's plugged in but maybe not in the exhaust do you?

[swsmotorsports]

Thanks for the help guys, I seem to have it sorted out. bad sparkplug wire that wouldn't fully snap onto the plug. it would fully snap onto the spark tester though. explains the intermittent misfire

does anyone know what sorts of MAF readings should be normal for a 6.0 with this size cam at WOT? I'm reading 30lbs/min and that seems low