Engine runs rough and shuts off when decelerating

1488MISSY

MEMBER
1990 CHEVROLET 1500
5.7L
V8
4WD
AUTOMATIC
125,000 MILES

Truck is a C1500

Vehicle Problem:
When giving it power it runs great, but when slowing down (like coming out of the driveway or coming up to a stop sign) it’ll start lopping really bad and sometimes shuts off but it’ll start right back up again and run fine until the next time you slow down.
Also goes into “limp” mode.

What I have tried so far:
Changed the throttle body, but not the gasket.

Diagnostics:
OBD is showing codes 43 and 44, tried to read code from book but don’t really understand the directions.
My husband is 71 years old and doesn’t need to be out in heat working on truck any longer than absolutely necessary, and any assistance or advice anyone out there can provide would be greatly appreciated. Thank you in advance for your assistance.

3 Replies

DANNY L

MECHANIC
5,648 POSTS

Hello, I'm Danny.

Code 43 is for Electronic Spark Control circuit and code 44 is for Lean exhaust indicated. I've attached picture test instructions below. Hope this helps and thanks for using 2CarPros.
Danny-

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Friday, May 10th, 2019 AT 5:03 PM

1488MISSY

MEMBER
5 POSTS

OMG! Thank you so much!
It sounds like this is our problem.
Code’s 43 and 44 seem to be related, or possibly one is secondary issue being caused by the initial problem. (Whichever/whatever may be)
Ironically, the “check engine light” isn’t coming on at initial startup, which cannot be a good thing as from what I think I understand. There’s a mechanical scan run at initial startup which is why the check engine light lights up and then (provides all is well) shuts itself back off. I was just reading to my husband (from pages 1-2 of the links) that you sent that and it mentions a diagnostic scan being run as well (page 1, code 43)
Again, thank you so very very much and i’ll message again tomorrow to let you know if it worked and if not, keep you updated. God Bless you and yours,
Jeff and Mychelle W.
Shasta County, California

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Friday, May 10th, 2019 AT 5:20 PM

DANNY L