5.3L LS checklist with part numbers

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Hunter79764

Full Access Member
Joined
Sep 1, 2021
Posts
222
Reaction score
292
Location
Grand Prairie, TX
First Name
Shawn
Truck Year
1987
Truck Model
Suburban V20
Engine Size
350
Don't underestimate making sure that cables and pivots are clean and/or lubricated. I had a high idle problem once that ended up being dirt on the cable hanging it up...
Aside from that, I think there's some Idle Air Control tuning that can cause a slower return to idle etc., but I'm not smart enough to know much beyond that.
 

iamtherealJayy

Full Access Member
Joined
Nov 26, 2021
Posts
1,571
Reaction score
275
Location
Tennessee
First Name
Jacob
Truck Year
1987, 1978, 1976
Truck Model
V20, K10, K10
Engine Size
350, 350, 350
The cable is great moves easy returns fine the return to idle is just slow, so if it’s tuning related I’ll deal with it for time being. I’ve also got an occasional slight idle surge. My tachometer doesn’t read right it shows 200 at idle and I have one code store, po650. I haven’t got the check engine light wired up yet.
 

iamtherealJayy

Full Access Member
Joined
Nov 26, 2021
Posts
1,571
Reaction score
275
Location
Tennessee
First Name
Jacob
Truck Year
1987, 1978, 1976
Truck Model
V20, K10, K10
Engine Size
350, 350, 350
Made more progress got the truck running and let the thermostat open, I have to redo the relay wiring for electric fans because guy that did the harness swore up and down that the green wire is the signal wire not the ground, well they never came on. Clutch adjusted and truck moves under its own power. I still need to button up a few small things before the first real drive
 

Camar068

Supporting Member
Supporting Member
Joined
Feb 5, 2014
Posts
4,122
Reaction score
2,957
Location
Kentucky
First Name
David
Truck Year
1986
Truck Model
K10/LM7 5.3/4L60e/np208/3.73/32"
Engine Size
10 yrs Air Force
Green should be the low speed fan control if you have the donor block/ckt for fan control. I'm guessing you don't have the fan controller block that contains everything in the schematic below. It would have came from your donor vehicle and not custom built.

Not knowing how it's wired up, but dark green and dark blue control low and high fans for a 2006 PCM in the schematic (bottom left of the ckt below).

If in doubt, go to LT1swap and look up your Year wiring harness to see if you have wires on the connectors at the PCM.

You must be registered for see images attach
 

iamtherealJayy

Full Access Member
Joined
Nov 26, 2021
Posts
1,571
Reaction score
275
Location
Tennessee
First Name
Jacob
Truck Year
1987, 1978, 1976
Truck Model
V20, K10, K10
Engine Size
350, 350, 350
I got a low fan working atleast with a green wire labeled fan 1, used it as ground for the relay and it did finally come on. I finally wired in my check engine light and it came on after a few minutes with two codes, knick sensor 2 circuit low voltage and po301. Great. I’m still waiting to get exhaust done before the first drive because the drivers side is about 2” past the o2 sensor and passenger side is maybe 5” past the o2 sensor
 

Elliot W

Full Access Member
Joined
Apr 13, 2021
Posts
147
Reaction score
250
Location
CT
First Name
Elliot
Truck Year
1974
Truck Model
C10
Engine Size
5.3
I had the knock sensor code on mine and had a couple clogged injectors. At least p0301 tells you it’s #1 cylinder so you don’t have to hunt for the problem area. Maybe it’s something as small as the spark plug not all the way connected.
 

iamtherealJayy

Full Access Member
Joined
Nov 26, 2021
Posts
1,571
Reaction score
275
Location
Tennessee
First Name
Jacob
Truck Year
1987, 1978, 1976
Truck Model
V20, K10, K10
Engine Size
350, 350, 350
That’s what I was thinking because I changed the plug wires since I broke one and the code didn’t come back yet, but I also haven’t drove it. I am having weird idle issues though. It occasionally surges, sounds like it’s got a blower and a big cam. I’ll try to get a video if I remember. I also need to figure out how to get a working tach, mine shows idle at like 200 and only revs up to like 1800. It’s way inaccurate. Changing modes only makes it worse lol
 

Bextreme04

Full Access Member
Joined
May 13, 2019
Posts
4,135
Reaction score
4,983
Location
Oregon
First Name
Eric
Truck Year
1980
Truck Model
K25
Engine Size
350-4bbl
That’s what I was thinking because I changed the plug wires since I broke one and the code didn’t come back yet, but I also haven’t drove it. I am having weird idle issues though. It occasionally surges, sounds like it’s got a blower and a big cam. I’ll try to get a video if I remember. I also need to figure out how to get a working tach, mine shows idle at like 200 and only revs up to like 1800. It’s way inaccurate. Changing modes only makes it worse lol
What tach are you using? If it's an aftermarket tach, you need to set it for 4cyl. If its a factory tach and you can't adjust it, the settings need to be adjusted in the tune to make the tach output correct.
 

iamtherealJayy

Full Access Member
Joined
Nov 26, 2021
Posts
1,571
Reaction score
275
Location
Tennessee
First Name
Jacob
Truck Year
1987, 1978, 1976
Truck Model
V20, K10, K10
Engine Size
350, 350, 350
It’s after market but the back where there’s usually a switch, has nothing, cheapo Amazon tach for ya I reckon. I have another one I can swap in later I’m focused on getting it running correctly currently.
 

louu

Full Access Member
Joined
Sep 19, 2020
Posts
184
Reaction score
308
Location
South NJ
First Name
Lou
Truck Year
1986
Truck Model
C3500
Engine Size
454 for now working on LS
This is a great thread with a lot of good info. @iamrherealjayy how is the project going? Been a little bit since your last post
 

iamtherealJayy

Full Access Member
Joined
Nov 26, 2021
Posts
1,571
Reaction score
275
Location
Tennessee
First Name
Jacob
Truck Year
1987, 1978, 1976
Truck Model
V20, K10, K10
Engine Size
350, 350, 350
Had the 350 out, ls in and fired up in four days. Waited around 3 weeks to get my existing exhaust welded up to find out 2” is too small, ordered full 2.5” exhaust and now I’m waiting on a drivers side manifold since I couldn’t get the studs out to replace them. The truck ran fine for the most part other than I have some sort of abuse mode that kicks in if I really rev it up, otherwise it went alright. Still have a couple small things to button up. Also swapped in 98 Chevy bucket seats and center console while I was at it.
 

iamtherealJayy

Full Access Member
Joined
Nov 26, 2021
Posts
1,571
Reaction score
275
Location
Tennessee
First Name
Jacob
Truck Year
1987, 1978, 1976
Truck Model
V20, K10, K10
Engine Size
350, 350, 350
Fabric on bled my own exhaust with clamps and an Amazon kit. Currently 2.5” straightpipe with 45° turndowns behind the rearend. Obnoxious, yes, will it do for now, also yes. Other than the idle surge and the truck stalled once it ran pretty good.
 

Latest posts

Forum statistics

Threads
41,847
Posts
903,379
Members
33,361
Latest member
iiixtremeiii
Top