5.3 falling on its face - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dme922 · 05-18-2017, 09:23 PM

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.

Lower · 05-18-2017, 09:53 PM

Are you running the o2 sensors?

dme922 · 05-18-2017, 09:54 PM

Quote:

Originally Posted by Lower

Are you running the o2 sensors?

Yes. They are in my header collectors

cdog73 · 05-18-2017, 10:51 PM

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.

sprint_9 · 05-18-2017, 11:34 PM

What has been done on the tune?

dme922 · 05-18-2017, 11:36 PM

Quote:

Originally Posted by sprint_9

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.

ls1nova71 · 05-18-2017, 11:41 PM

What's your fuel pressure?

dme922 · 05-18-2017, 11:44 PM

Quote:

Originally Posted by ls1nova71

What's your fuel pressure?

I am going to check that this weekend when im off work. I was just looking for some ideas.

Custom 68 · 05-19-2017, 10:57 AM

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
Dave

**Hart_Rod** · 05-19-2017, 11:47 AM

Make sure your O2s are plugged into the correct side.

dme922 · 05-22-2017, 09:58 AM

Thanks. Ill check that out. One thing i did find out this weekend is that my ecm is losing communication for some reason.

**Hart_Rod** · 05-22-2017, 11:13 AM

Do you have your exhaust system installed?

dme922 · 05-22-2017, 11:21 AM

Quote:

Originally Posted by Hart_Rod

Do you have your exhaust system installed?

Yes

**Hart_Rod** · 05-22-2017, 12:44 PM

Quote:

Originally Posted by dme922

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?

dme922 · 05-22-2017, 12:59 PM

Quote:

Originally Posted by Hart_Rod

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.

akdg87 · 05-22-2017, 02:29 PM

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..

BR3W CITY · 05-22-2017, 08:01 PM

Quote:

Originally Posted by dme922

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.

dme922 · 05-22-2017, 08:35 PM

Quote:

Originally Posted by BR3W CITY

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.

Robznob11 · 05-23-2017, 11:08 PM

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.

dme922 · 05-24-2017, 08:45 AM

Quote:

Originally Posted by Robznob11

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

05-18-2017, 09:23 PM	#1
dme922 Registered User Join Date: Mar 2012 Location: Gallipolis, Ohio Posts: 296	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.

05-18-2017, 09:53 PM	#2
Lower Registered User Join Date: Feb 2012 Location: Depew, OK Posts: 204	Re: 5.3 falling on its face Are you running the o2 sensors? __________________ ~Jon Ol Green 1970 K10ish LWB,454/400/205, been in family since new. My build thread http://67-72chevytrucks.com/vboard/s...d.php?t=516056

05-18-2017, 10:51 PM	#4
cdog73 Registered User Join Date: Mar 2013 Location: Kendallville, Indiana Posts: 83	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.

05-18-2017, 11:34 PM	#5
sprint_9 Registered User Join Date: Nov 2012 Location: 9 Posts: 862	Re: 5.3 falling on its face What has been done on the tune?

05-18-2017, 11:41 PM	#7
ls1nova71 Registered User Join Date: Dec 2009 Location: Independence Mo Posts: 4,118	Re: 5.3 falling on its face What's your fuel pressure? __________________ My '72 short bed build. http://www.ls1tech.com/forums/conver...6-0-4l80e.html 5.3 swap into my RUSTY '71 C10 http://ls1tech.com/forums/conversion...71-c-10-a.html

05-19-2017, 10:57 AM	#9
Custom 68 Registered User Join Date: Nov 2001 Location: Springfield, MO Posts: 2,930	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 Dave __________________ Dave 1968 Custom Chevy with turbo charged 5.3 gen III 4l80e swap 1967-71 GMC 3/4 ton long step 4x4 (not sure what year exactly?) "A good friend will bail you out of jail...but a true friend will be sitting next to you saying "that was frekin awesome". "If it doesn't fit force it...If it breaks then it needed to be replaced anyway!"

05-19-2017, 11:47 AM	#10
Hart_Rod ************* Join Date: Apr 2005 Location: Pensacola, FL Posts: 17,827	Re: 5.3 falling on its face Make sure your O2s are plugged into the correct side. __________________ Rob - https://www.instagram.com/hart_rod_c10 As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17 FOR SALE: DBW pedal bracket - http://67-72chevytrucks.com/vboard/s...d.php?t=651123 FOR SALE: Hood Brackets http://67-72chevytrucks.com/vboard/s...d.php?t=679945 1987 Silverado SWB - 34.5K original miles http://67-72chevytrucks.com/vboard/s...d.php?t=801834 1969 SuperBurb - http://67-72chevytrucks.com/vboard/s...d.php?t=200387 1968 Farm truck - http://67-72chevytrucks.com/vboard/s...d.php?t=358692 1968 SWB - http://67-72chevytrucks.com/vboard/s...d.php?t=551258 1948 Chevy - http://67-72chevytrucks.com/vboard/s...=122164&page=3

05-22-2017, 09:58 AM	#11
dme922 Registered User Join Date: Mar 2012 Location: Gallipolis, Ohio Posts: 296	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.

05-22-2017, 11:13 AM	#12
Hart_Rod ************* Join Date: Apr 2005 Location: Pensacola, FL Posts: 17,827	Re: 5.3 falling on its face Do you have your exhaust system installed? __________________ Rob - https://www.instagram.com/hart_rod_c10 As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17 FOR SALE: DBW pedal bracket - http://67-72chevytrucks.com/vboard/s...d.php?t=651123 FOR SALE: Hood Brackets http://67-72chevytrucks.com/vboard/s...d.php?t=679945 1987 Silverado SWB - 34.5K original miles http://67-72chevytrucks.com/vboard/s...d.php?t=801834 1969 SuperBurb - http://67-72chevytrucks.com/vboard/s...d.php?t=200387 1968 Farm truck - http://67-72chevytrucks.com/vboard/s...d.php?t=358692 1968 SWB - http://67-72chevytrucks.com/vboard/s...d.php?t=551258 1948 Chevy - http://67-72chevytrucks.com/vboard/s...=122164&page=3

05-22-2017, 02:29 PM	#16
akdg87 Registered User Join Date: Sep 2013 Location: fairbanks, ak Posts: 339	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.. __________________ build thread 1955 cameo turbo lsx 1993 K1500 Blazer 5.3/4L80e 2009 CTSV Sedan

05-23-2017, 11:08 PM	#19
Robznob11 Registered User Join Date: Feb 2004 Location: brownfield texas (west texas) Posts: 1,936	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. __________________ The Ghost 67 short wide full custom. 550 hp LSX, 4l80E, narrowed 9". Body dropped w/air ride! ........................ ___ .........________//__{\_____ ,,,,,,,/__(⊙)___//___/__(O)_/ @disciple2.rc 💪instagram💪 LED TAILS



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