07 Suburban rough idle P0304 code afm delete

[smokymtn65]

So i thought I would start my own thread here. Hopefully for some help to figure out what is going on. As title says Did a delete, using a BTR stage 2 truck cam. And it has been tuned. I have a rough idle and will throw code P0304 after time, Today I drove it in to work 50 miles no code had a bit of rough idle when started but not bad. I stopped for gas and it was more rough after restart. a mile later the stabil-a-trac lit up and then had a pending P0304. one more mile to work and idle was pretty rough and it smells like it's running rich.. I did have and issue after the cam install, my young helper apparently drooped a intake bolt in the intake runner of cylinder 4 head. so it lodged enough it went partially through and the intake valve got bent. I replaced the valve they were very little visible damage the head or piston I seated the valve using compound and mating surfaces were looking good. The compression check afterward was 150 on 4 and 150 on 2 I do not go further since they were so close. I have moved all components from 4 to 2 one at a time to eliminate injector, coil, plug wire, and plug, The computer is triggering to injector by test light in ground side. I used a spark checker and it lights from the coil. All ideas and help Appreciated!! I also has a hot hard start issue after sitting for 20 minutes it will take 2 cranks sometimes to start and smells like raw fuel. Thanks @kbuskill for your input so far. And @randeez as well

 

[kbuskill]

So i thought I would start my own thread here. Hopefully for some help to figure out what is going on. As title says Did a delete, using a BTR stage 2 truck cam. And it has been tuned. I have a rough idle and will throw code P0304 after time, Today I drove it in to work 50 miles no code had a bit of rough idle when started but not bad. I stopped for gas and it was more rough after restart. a mile later the stabil-a-trac lit up and then had a pending P0304. one more mile to work and idle was pretty rough and it smells like it's running rich.. I did have and issue after the cam install, my young helper apparently drooped a intake bolt in the intake runner of cylinder 4 head. so it lodged enough it went partially through and the intake valve got bent. I replaced the valve they were very little visible damage the head or piston I seated the valve using compound and mating surfaces were looking good. The compression check afterward was 150 on 4 and 150 on 2 I do not go further since they were so close. I have moved all components from 4 to 2 one at a time to eliminate injector, coil, plug wire, and plug, The computer is triggering to injector by test light in ground side. I used a spark checker and it lights from the coil. All ideas and help Appreciated!! I also has a hot hard start issue after sitting for 20 minutes it will take 2 cranks sometimes to start and smells like raw fuel. Thanks @kbuskill for your input so far. And @randeez as well

Did you happen to check the constant power side of the injector to make sure it is getting power?

I only ask because you specifically mentioned the triggered ground side which means you could have had your test light hooked to the positive terminal of the battery while checking.

 

[smokymtn65]

Yes I check it as well, It was steady on with key on. Thanks need all the help I can get LOL

 

[smokymtn65]

An update after sitting for 3 hours I started it up and let it idle for a a few minutes the pending p0304 went away and was replaced with a P0300 so guess I will just have to start checking all cylinders.

 

[Geotrash]

Have you checked the fuel pressure at idle on the fuel rail?


Sent from my iPhone using Tapatalk

 

[smokymtn65]

Have you checked the fuel pressure at idle on the fuel rail?


Sent from my iPhone using Tapatalk

I had when I was dealing with hard start a little before I pulled right head, it was 51psi on my HF gauge. I do need to check again. THX

 

[smokymtn65]

Have you checked the fuel pressure at idle on the fuel rail?


Sent from my iPhone using Tapatalk

I checked it again last night 59psi steady at idle.

 

[kbuskill]

I checked it again last night 59psi steady at idle.

Is this a flex fuel truck?

59 psi is pretty high for a flex fuel engine/pump.

The flex fuel pumps are commanded to 43.5 psi
from the factory.

 

[smokymtn65]

Is this a flex fuel truck?

59 psi is pretty high for a flex fuel engine/pump.

The flex fuel pumps are commanded to 43.5 psi
from the factory.

Yes it is a flex fuel.

Sent from my SM-G960U using Tapatalk

 

[kbuskill]

Yes it is a flex fuel.

Sent from my SM-G960U using Tapatalk

I wonder if your tuner jacked up the fuel pressure in the tune?

I would think having the higher fuel pressure with the bigger flex fuel injectors could be dumping too much fuel, but I would also think the O2 sensors would realize that it was rich and compensate for it as well.

Someone with more tuning experience will hopefully chime in.

@randeez @swathdiver

 

[smokymtn65]

I wonder if your tuner jacked up the fuel pressure in the tune?

I would think having the higher fuel pressure with the bigger flex fuel injectors could be dumping too much fuel, but I would also think the O2 sensors would realize that it was rich and compensate for it as well.

Someone with more tuning experience will hopefully chime in.

@randeez @swathdiver

I have had an on and off noise that sounds like an injection knock in a diesel (idi) i have spent a lot more time under the hood of those
Lol, i will try to link a recording.

Sent from my SM-G960U using Tapatalk

 

[randeez]

a fpcm truck will have a base pressure of 43psi...under high load, warm up, cranking conditions it goes up to 58psi

 

[smokymtn65]

Good to know so back to square one! lol

 

[smokymtn65]

Still no progress on this CANDI module won't work on my TECH2 so still dealing with a idle miss. Have new module on the way maybe can figure out something.

Sent from my SM-G960U using Tapatalk

 

[smokymtn65]

 

[smokymtn65]

Anyone see anthing odd here , still chasin4 cyl 4 missfire at idle

 

[wsteele]

Still no progress on this CANDI module won't work on my TECH2 so still dealing with a idle miss. Have new module on the way maybe can figure out something.

Sent from my SM-G960U using Tapatalk

My CANdi module wouldn't work when I got my Tech 2. I found out a pin on the RS232 connector was bent. I straightened the bent pin and it fired up and works fine now. I leave it connected all the time now as the pins on that connector are very soft metal and will bend easily.

 

[smokymtn65]

Update , Had a continuing issue on #4 so pick up a set of heads and had them reworked. Only to cut down on downtime. swapped heads on Saturday 2 weeks ago. Truck ran better but misfire continued, as well as hard start after heat soak. Set up time to take back to tuner as I felt I have exhausted most "mechanical" fixes. He had it for 3 days didn't get to it. I picked it up and pulled are 6K travel trailer 100miles pulls good till you idle. took it back to tuner after another three days says come get it. All the details I got were " I changed a bunch of stuff, pulled valve covers, looked at a lot of stuff. and checked a lot of grounds. when I got it back together the miss was gone. " So no miss now, idle is not real smooth but the motor mounts do transfer some of the vibration i am sure. And sitting at idle it will rhythmically cut out every 10 seconds or so.

 

[smokymtn65]

My CANdi module wouldn't work when I got my Tech 2. I found out a pin on the RS232 connector was bent. I straightened the bent pin and it fired up and works fine now. I leave it connected all the time now as the pins on that connector are very soft metal and will bend easily.

I did look at my Tech 2 and it does not have the latest update in it , I guess that probably is a issue for no recognizing the CANDI mine is 27. something not 34 Anyone else know on this?

 

[Geotrash]

I did look at my Tech 2 and it does not have the latest update in it , I guess that probably is a issue for no recognizing the CANDI mine is 27. something not 34 Anyone else know on this?

@swathdiver