67-72 GM Truck Gen IV Swap

[Motoxrrar]

First, I am a newbie so my apologies for my pure lack of Knowledge and experience.

I have a 72 GMC 3/4 Ton truck that I completed a motor swap in.
Took to a local tuner to get it running. They did a little, but didn't really help fully. So I decided to do it myself. There seems to be a lack of capable shops here in my area.

4.8 Gen IV from a 2007 Silverado
4L80E from 2012
3.53 Gears in a Dana 60 rear diff

I had played with the software a bit to get the truck more driveable shift points and such.
Its ok for now.
Had some issues with the fans not kicking on. Sorted that out. Doesnt get over 201 degrees now.

My current issue is a misfire that will happen on occasion on cyclinder 1.

PO300
PO301

When this happens I can feel and hear the misfire.
Not sure if its mechanical or software related.
To me it feels like when a vehicle goes into limp mode.
Like when my fan went out and I was in traffic so it got so hot it cut out cylinders.

I tried changing plug wires.
And sometimes cycling the key on off works
Cleaning the codes
Disconnecting Battery

Just not sure where to start.
Any Help is appreciated.


On a side note unrelated, at some point id like knock a few to do's off my list.

Stock RPM gauge
Speedometer
Temperature gauge

If anyone has any experience in getting these stock instruments working with Gen IV motors I could use the help.

[5FDP]

It seems you may have a dead or dying o2 sensor too, maybe even wiring issue. The bank 1 o2 sensor is often at 70mv or less and does not move around as much as the bank 2 sensor. Though both sensors do seem to drop out to nothing at random times.

If this vehicle has headers that can be another reason for the wacky o2 sensors. Also assuming this vehicle has no cat converters because all the rear o2 sensors are shut off, you must disable the post cat o2 sensor test and the cat test itself in the engine diag tab. Leaving those on can make fueling do some weird things.

[Motoxrrar]

It seems you may have a dead or dying o2 sensor too, maybe even wiring issue. The bank 1 o2 sensor is often at 70mv or less and does not move around as much as the bank 2 sensor. Though both sensors do seem to drop out to nothing at random times.

If this vehicle has headers that can be another reason for the wacky o2 sensors. Also assuming this vehicle has no cat converters because all the rear o2 sensors are shut off, you must disable the post cat o2 sensor test and the cat test itself in the engine diag tab. Leaving those on can make fueling do some weird things.

It does have headers and no CAT.
I will double check the O2 sensors tomorrow and Disable the Post CAT test and see if that helps.

Dude I see you respond to almost all posts and I really appreciate your thoroughness .
You rock man, I wish I had your knowledge and understanding of this stuff.

[Motoxrrar]

Just a quick update. I had disabled the Post CAT o2 test and the CATYLIST test this morning. Still seems a to be fairly the same. Sometimes the issues are intermittent. But still seems underpowered and a slight miss. Ill be getting an O2 Sensor to replace that bank 1 and ill run another log file on it and post after I get off work.

[Motoxrrar]

So I disabled the Post CAT 02 Test and CAT Test and also replaced bank 1 o2 Sensor and I seem to have the same struggles. Ill attach my log file anyone have any ideas?

[Motoxrrar]

Well I have been a little busy, But I did get some good info and changed and trouble shot a little.

Changed both o2 sensors.

Seem to have a miss in cylinder 1 that I am trying to trouble shoot.

Swapped Plugs, Wires and Coil with cylinder 1 and 2 and did not seem to get a change. When I pulled plug number 1 I did notice that the end of the plug was Wet looking as opposed to cylinder 2 looked pretty good not running too rich or lean, dry.

I have attached just a small log of the truck starting and then backing into my garage, and it shows a lot of misses for cylinder 1.

Can anyone help me figure this out?

Do I still have an o2 sensor issue ? or just my cylinder miss or both?

[Earwax]

Make sure you have spark and compression on the cyl that misses.
Use an HEI spark tester,like a ST125. AC and KD make them.
Check the wiring on the coil both at the coil and the harness plug.
There should be 12 volts on the pink wires. The black wires are GND.

[Motoxrrar]

So I check all of that and was able to do a little testing and got to the point of it possibly being an injector.

Upon removing bolts for the fuel rail I had made a mistake and put my 8mm socket/ratchet on an intake manifold bolt. To my surprise the bolts had only been finger tight.
This is a little strange because I had no sign of a vacuum leak. I do have a mechanical gauge that reads anywhere from 5-20 psi depending on rpm. No hissing or any other sort of sign. I have vacuum actuated vent doors in my truck that work fine and brake booster works just fine. So no sign of a vacuum leak. But anyway I tightened those bolts, and just for shits and giggles I swapped number 1 and 2 injectors to see if the problem would move to another cylinder. But all is fine and things seem much better.

If anyone cares to look at my log file now that the truck seems to be running very well now, if you see any concerns or room for improvement I am all ears.

Thanks again to EARWAX to go with basic troubleshooting.
And a shout out to 5FDP for pointing out a dead o2 sensor.

Attached is my latest log.09-08-17 3pm.hpl

[Earwax]

I would enable the LTFT. Set enable temp to 130*.
Set the PE /EQ ratio to 1.17 which would be slightly richer than you currently are.12.75-12.5.
Retest and post the log.
It looks rich, but without more info from the LTFT.It will be easier with the LTFT info.

[Motoxrrar]

I would enable the LTFT. Set enable temp to 130*.
Set the PE /EQ ratio to 1.17 which would be slightly richer than you currently are.12.75-12.5.
Retest and post the log.
It looks rich, but without more info from the LTFT.It will be easier with the LTFT info.

Thanks Earwax

I will make these changes and repost Monday or Tuesday.

[Motoxrrar]

I would enable the LTFT. Set enable temp to 130*.
Set the PE /EQ ratio to 1.17 which would be slightly richer than you currently are.12.75-12.5.
Retest and post the log.
It looks rich, but without more info from the LTFT.It will be easier with the LTFT info.

I was able to change the PE/EQ ratio just fine.

But changing Temp to 130*
and Enabling LTFT

These two things I was unable to figure out.
Any suggestions as a process to complete this. I didnt see an option to edit the temperature on here.example screen.jpg

[5FDP]

You are looking in the wrong area. The Long Term Fuel Trim settings are under Engine > fuel > open/closed loop.

The LTFT min enable temp is set to 284, he was saying to lower that to 130.

[Motoxrrar]

You are looking in the wrong area. The Long Term Fuel Trim settings are under Engine > fuel > open/closed loop.

The LTFT min enable temp is set to 284, he was saying to lower that to 130.

Got it Thanks 5FDP!!

My apologies I am so green, new, noob. Just trying to learn.

Made the changes, will flash later today and then try to get a drive in after work.

[Motoxrrar]

Alright !
LTFT on at 130*
PE/EQ values redefined as 1.17

New Log file attached

Now lets see... how that tune is

[Motoxrrar]

bump