# 1985 GMC 1500 - Carb? **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** gmc\ **Created:** [August 23, 2018, 5:10pm UTC](https://community.cartalk.com/t/1985-gmc-1500-carb/123528 "2018-08-23T17:10:37Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![chrispelloni](https://avatars.discourse-cdn.com/v4/letter/c/ebca7d/32.png) [@chrispelloni](https://community.cartalk.com/u/chrispelloni)\ **Post date:** [August 23, 2018, 5:10pm UTC](https://community.cartalk.com/t/1985-gmc-1500-carb/123528/1 "2018-08-23T17:10:37Z")
I am having trouble with my truck hesitating when its under a heavy load. it has a quadrajet carb, I have recently changed the plugs wires cap rotor pcv coil coil cap. it seams to run fine until I need the four barrel to kick in, it will loose power hesitate ,sputter, and also has a signifigant spark knock. any ideas about what the malfunction is? ---
**Author:** ![Chris\_Pelloni](https://avatars.discourse-cdn.com/v4/letter/c/8baadc/32.png) [@Chris\_Pelloni](https://community.cartalk.com/u/Chris_Pelloni)\ **Post date:** [August 23, 2018, 5:12pm UTC](https://community.cartalk.com/t/1985-gmc-1500-carb/123528/2 "2018-08-23T17:12:24Z")
it has a 4.3 v-6 with a 4 barrel carb ---
**Author:** ![oldtimer-11](https://avatars.discourse-cdn.com/v4/letter/o/e79b87/32.png) [@oldtimer-11](https://community.cartalk.com/u/oldtimer-11)\ **Post date:** [August 24, 2018, 4:01am UTC](https://community.cartalk.com/t/1985-gmc-1500-carb/123528/3 "2018-08-24T04:01:23Z")
Check for vacuum leaks. ---
**Author:** ![Chris\_Pelloni](https://avatars.discourse-cdn.com/v4/letter/c/8baadc/32.png) [@Chris\_Pelloni](https://community.cartalk.com/u/Chris_Pelloni)\ **Post date:** [August 24, 2018, 12:24pm UTC](https://community.cartalk.com/t/1985-gmc-1500-carb/123528/4 "2018-08-24T12:24:08Z")
I thought I found them all. i’ll check for more. thanks