Major misfire problems.

2002 5.3l L59 flex fuel into a 98 k1500

Got everything hooked up and the the truck runs, however it runs like crap. I have a P0200 and P0300, which is injector circuit and random misfires. So far I have hooked up a noid light and the injectors are pulsing. I have verified the wiring for the coils, the injector wiring was not changed except for swapping a few of the wires around. I checked a few of the coils and plugs by grounding against the block and spark was present. I have EFI live and I have misfires on every cylinder, along with 0mv on bank 1 sensor 1 02 sensor, however no codes for that. Fuel pressure at the rail is 40 PSI.

Before doing this swap there were no codes and no issues with my truck, and I was running the same computer. The 0411 that I am using came with the L59, so I flashed it with the original stock tune when I did the swap.

I'm thinking that the fuel pressure regulator is bad, since fuel pressure should be around 48-54 PSI, but what other issues could be causing misfires on every cylinder?

Edit: All fixed now. The PCM pins for 6 and 8 were pushed back into each other and shorting out. Once that was fixed everything was running correctly. It was discovered by taking a multimeter and checking the frequency of the injector pulses, 6 and 8 were showing a higher frequency than the other cylinders.

if using stock tune for injectors you need much higher base fuel pressure. stock GMs see 58 for most part and that could be causing your issues since your injectors are scaled for the lower psi

The injectors are the stock flex fuel injectors, which run 33lbs at 48 PSI. I'm using the stock tune, so I don't think this is the issue.

So I replaced the regulator and it still showed 40 PSI. Sometimes it will go up to 50 though, and when I pinch the return line I can control the pressure. However, none of this has made a difference in curing the misfires. I pulled the injectors and send them to be ultrasonically cleaned, since I don't know their history. If this doesn't fix the issue then I'm out of ideas.

if you are at 40psi and tune is stock then the scaling is off

you either need to scale injectors for 40psi or figure out how to raise pressure

I was able to raise the pressure by crimping the return fuel line and it made no difference.

Quote:

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Originally Posted by crzy8mnky

I was able to raise the pressure by crimping the return fuel line and it made no difference.

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crimping the line now restricts volume....motors need to see a certain psi and a certain volume

It was the return line, not feed. Regardless, it did not seem to make a difference as the truck ran poorly no matter what the pressure was at.

restricting any line will cause issues but either way any time i seen your issues it was purely a fuel delivery issue

That's what I'm thinking, especially since both O2 sensors are showing lean. Hopefully getting the injectors cleaned will take care of it The weird thing with the rail pressure is that immediately when I turn the key it will jump to 50, and then the pump will shut off and it will drop to 40. And when it's running it will go anywhere from 37 to 50. The first regulator was a brand new AC Delco part and this new one is a BWD and the same thing occurs.

I got the injectors cleaned and placed back into the truck, no change. I am misfiring the most on 1-4, with a few misfires on 5 and 7, and very few on 6 and 8. I have 12 volts on pink, and there is about .7 ohms of resistance on the ground wire on 7 of them, the 8th one if 1.7 ohms. Noid light flashed on all 8. Still have the p0200 and p0300 codes with a lean condition on bank 1. One thing I noted is that when I unplug the MAF the truck seems to be running better, although it seems that the MAF being disconnected means that the misfire counter on EFI does not work, however both O2 sensors are around 800-900 mv. I'm using the original MAF. I'm pretty much out of ideas so any ideas are appreciated.

I ended up recalibrating the MAF to the 98 one and that problems seems to have gone away. I'm still getting the p0200 and p0300 codes though, with both 6 and 8 misfiring quite a bit. 5 and 7 are misfiring a little bit, but I'm not sure that it is enough to trip the code. I'm going to pull out the plugs and clean them up, and then make a test harness for the injectors so that I can connect both 6 an 8 to the computer without going through the original harness. Perhaps I damaged the harness when I was rewiring things. I pull a 5.3 harness out of the junkyard today, so if it turns out the stock wiring is damaged, I will replace it with the 5.3 harness.

I took off the intake manifold and there was oil on the inside of the o ring on both cylinders 6 and 8. Bad PCV valve?

As long as you use stock pcv system you'll have oil

I still say fuel supply is your issue

Where is the harness from or did you modify it?

Fuel pressure at the rail is in the right range and the injectors were just cleaned and flowed fine. However the 6 and 8 plugs were carbon fouled when pulled out. I don't know what else to test for in the fuel system. The harness is the modified 5.7 harness. Noid lights showed all 8 injectors were being pulsed and I have 12 volts on the pink wires to the injectors, along with .3 to .5 ohms on the ground wires to the computer. I even swapped in a wire directly to the computer to control the injectors with no change. The coil wiring was pulled from the harness that came with the engine. I hooked it up like lextech described in the wiring file.

One thing to note, when I turned off cylinders 4 or 7 with efi live, the truck seemed to smooth out. When I turned off any other cylinder, the truck got worse.

Need to verify the wire locations on the computer to the injectors and coils for those cylinders. Could you post up where you have them pinned in please.

From lextech's file:
a Purple wire to------C2-26 for Coil #1 Control
a Red wire to---------C2-27 for coil #4 Control
a Lt.Blu/Wht wire to--C2-28 for coil #6 Control
a Dk.Grn/Wht wire to--C2-29 for coil #7 Control
a Purple/Wht wire to--C2-66 for coil #8 control
a Red/Wht wire to-----C2-67 for coil #3 control
a Dk.Grn wire to------C2-68 for coil #5 control
a Lt.Blu wire to------C2-69 for coil #2 control
a Brown wire to C2-60 for Bank #1 Coils-Low Reference
a Brn/Wht wire to C2-61 for Bank #2 Coils-Low Reference

And for the injectors, I just swapped 2/3 and 4/7. There were no problems when I had done the 0411 swap.

I've verified these multiple times. I've also pulled the plug and held it against the block and there was spark. I don't know how to tell if it's hot enough though.

In that file 4 & 7 are backwards I believe. I checked it against 2 other files and they are switched. Try that

One other thing I want to throw out there. When I pulled the vacuum line off the brake booster to the intake, there was a pressure difference, and it does seem like my brakes are harder than they use to be.

Right now I have C1-43 for injector 7 and C1-44 for injector 4.

Edit: I think you mean for the coils, since the solid colors control the odd banks and the stripes control the even banks. The labels are wrong, but the colors match the diagrams that I have.

Switch c2-27 and c2-29 at the PCM. That should get it running ok

I checked the pin outs and they are correct to the other 5.3 wiring harness. The labels are wrong in the file, but the wire colors are correct, and that's what I went by when putting in my coil harness. I had just removed both coil pack harnesses from the wiring harness that came with the truck. It's not a vacuum leak either, I put my hand over the intake and it suffocated and help pressure.

Well dang.

What is running pressure again?

Right around 50 PSI. L59 are supposed to have 48 to 54 PSI.

What is a l59?

My jeep base is 50 and i had to scale back the injectors. Its a difference of 5lb worth of flow from typical base of 58.

Made a huge difference in how it idled and ran.
Since all injector data is based off of everything not just one thing.

Quote:

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Originally Posted by crzy8mnky

Right now I have C1-43 for injector 7 and C1-44 for injector 4.

Edit: I think you mean for the coils, since the solid colors control the odd banks and the stripes control the even banks. The labels are wrong, but the colors match the diagrams that I have.

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I somehow had two different versions of that. One on my home laptop and one on my work laptop. I have since deleted the other version. This one "should" be correct.

11. You will be adding:
a Purple wire to-------------------C2-26 for Coil #1 Control
a Dk.Grn/Wht wire to------------C2-29 for Coil #4 Control
a Lt.Blu/Wht wire to--------------C2-28 for Coil #6 Control
a Red wire to----------------------C2-27 for Coil #7 Control
a Purple/Wht wire to------------C2-66 for Coil #8 control
a Lt.Blu wire to--------------------C2-69 for Coil #3 control
a Dk.Grn wire to------------------C2-68 for Coil #5 control
a Red/Wht wire to---------------C2-67 for Coil #2 control
a Brown wire to C2-60 for Bank #1 Coils-Low Reference
a Brn/Wht wire to C2-61 for Bank #2 Coils-Low Reference

I missed the 2 & 3 being wrong. Hopefully that helps.

I have:
C2-26 Purple, coil 1
C2-27 Red, coil 7
C2-28 Lt Blue, coil 6
C2-29 Dk green/ White, coil 4
C2-66 Purple/ White, coil 8
C2-67 Red/ White, coil 2
C2-68 Dark Green, coil 5
C2-69 Lt blue, coil 3

And the L59 is the flex fuel version of the LM7. Larger injectors and lower fuel rail pressure.

That wiring is correct.

Jeff

Ok I might have found something. I checked the hertz for each of the each injectors on bank 2. Cylinders 2 and 4 were around 4.5 hz when at idle, but 6 and 8 were around 7.5 hz. Is it normal for the injectors to be getting pulsed at a different frequency? I would have thought that they should be pulsed at the same rate.

There is .7 ohms resistance between the pcm control wire for injector 6 and injector 8. I disconnected the pcm plug for the injectors and the continuity goes away. Internal fault in the PCM?

Edit: Took the PCM apart at the pins for 6 and 8 were touching. Moved them apart at it ran better, but still misfiring on 6. The p0200 code is gone, but p0300 is still present. Once the engine cools off I'm going to take the plug out and clean it, and move some stuff around.