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Old 05-18-2017, 09:23 PM   #1
dme922
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5.3 falling on its face
I am having an issue with my 5.3 falling on its face at a hard take off. It smells like it is running rich when i let it idle in the garage and rev it up. Need some ideas on what to check. It is dbw with a return style fuel set up and a th350 behind it.
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Old 05-18-2017, 09:53 PM   #2
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Re: 5.3 falling on its face
Are you running the o2 sensors?
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Old 05-18-2017, 09:54 PM   #3
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Re: 5.3 falling on its face
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Are you running the o2 sensors?
Yes. They are in my header collectors
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Old 05-18-2017, 10:51 PM   #4
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Re: 5.3 falling on its face
hope you get some info, cause I just completed my install a few weeks ago and now my truck is doing the same exact thing. I have a Boyd Welding fuel tank with an in tank pump, and I feel its either a air or fuel issue. it ran fine for about two weeks and now this issue just popped up. Stopped at the parts store and it isn't throwing any codes. I'm stumped.
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Old 05-18-2017, 11:34 PM   #5
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Re: 5.3 falling on its face
What has been done on the tune?
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Old 05-18-2017, 11:36 PM   #6
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Re: 5.3 falling on its face
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What has been done on the tune?
I got my ecm from a board member and as far as i know he just deleted the stuff i didnt need.
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Old 05-18-2017, 11:41 PM   #7
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Re: 5.3 falling on its face
What's your fuel pressure?
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Old 05-18-2017, 11:44 PM   #8
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Re: 5.3 falling on its face
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What's your fuel pressure?
I am going to check that this weekend when im off work. I was just looking for some ideas.
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Old 05-19-2017, 10:57 AM   #9
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Re: 5.3 falling on its face
Make sure all your fuses are good and the fuel pressure check out as well. Then you will need to talk to the tuner or decide on getting it tuned. With the TH350 it may be looking for some info (speed and such) from the trans it is not getting. I have not studied swapping for an old style trans. I know it can be done but I am not sure on tuning it. Maybe nothing? I have ran a 4l60, t56 and currently a 4l80 but those all have provisions for the computer.
Are you running exhaust?
Do you have a check engine light if so is it on?
good luck
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Old 05-19-2017, 11:47 AM   #10
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Re: 5.3 falling on its face
Make sure your O2s are plugged into the correct side.
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Old 05-22-2017, 09:58 AM   #11
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Re: 5.3 falling on its face
Thanks. Ill check that out. One thing i did find out this weekend is that my ecm is losing communication for some reason.
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Old 05-22-2017, 11:13 AM   #12
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Re: 5.3 falling on its face
Do you have your exhaust system installed?
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Old 05-22-2017, 11:21 AM   #13
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Re: 5.3 falling on its face
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Do you have your exhaust system installed?
Yes
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Old 05-22-2017, 12:44 PM   #14
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Re: 5.3 falling on its face
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Originally Posted by dme922 View Post
Thanks. Ill check that out. One thing i did find out this weekend is that my ecm is losing communication for some reason.
ECM is losing connection with what? DBW pedal?
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Old 05-22-2017, 12:59 PM   #15
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Re: 5.3 falling on its face
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ECM is losing connection with what? DBW pedal?
We were trying to see what was going on with my fan trigger wires and when the temp reached 205 ( thats where the guy i got my ecm set it was set to come on) is when it said lost communication.
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Old 05-22-2017, 02:29 PM   #16
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Re: 5.3 falling on its face
i was running a th350 with my 5.3 and every time it lost the speed sensor signal it fell on its face; it would retard the ignition (verified with hp tuners scanner) and run like complete crap.

There are some settings you can change in the tune but i could never figure out which one. I eventually swapped to a 4l80, but still have the dakota digital sensor laying around if you need one..
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Old 05-22-2017, 08:01 PM   #17
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Re: 5.3 falling on its face
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Originally Posted by dme922 View Post
We were trying to see what was going on with my fan trigger wires and when the temp reached 205 ( thats where the guy i got my ecm set it was set to come on) is when it said lost communication.
I want to be clear on this issue. Is the ECM triggering a code/error saying it lost connection (like one of the U-codes)?

Or is it actually disconnecting if your watching a data log/live feed?

Any updates on your other troubleshooting?
(btw smelling rich at idle is normal for these if its a stock tune with bolt-on's, the stock tunes are fat for safety from the factory, and depending on the setup the ecm might even be running it even fatter, depending what the ECM is seeing for air flow.
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Old 05-22-2017, 08:35 PM   #18
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Re: 5.3 falling on its face
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Originally Posted by BR3W CITY View Post
I want to be clear on this issue. Is the ECM triggering a code/error saying it lost connection (like one of the U-codes)?

Or is it actually disconnecting if your watching a data log/live feed?

Any updates on your other troubleshooting?
(btw smelling rich at idle is normal for these if its a stock tune with bolt-on's, the stock tunes are fat for safety from the factory, and depending on the setup the ecm might even be running it even fatter, depending what the ECM is seeing for air flow.
He had it hooked up to a tech 2 computer and when it reached the set temp for the fans is when he said it lost communication. I did not see what his computer said.
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Old 05-23-2017, 11:08 PM   #19
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Re: 5.3 falling on its face
Be sure to check the fuel psi under load! Also if your mass air meter is not plumbed correct it can do that. Some people put it close to the tb and it will jack up the readings causing all sorts of mess.
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Old 05-24-2017, 08:45 AM   #20
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Re: 5.3 falling on its face
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Originally Posted by Robznob11 View Post
Be sure to check the fuel psi under load! Also if your mass air meter is not plumbed correct it can do that. Some people put it close to the tb and it will jack up the readings causing all sorts of mess.
I checked the fuel pressure and it checked out good under a load. My maf sensor is mounted close to the tb due to the engine cover im using so i will put the regular cold air intake on and see what happens. Thanks
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