89 burban 350tbi runs rough

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.

Chaz

Full Access Member
Joined
Oct 12, 2012
Posts
192
Reaction score
13
Location
USA
First Name
Chaz
Truck Year
1980
Truck Model
V1500 Suburban
Engine Size
350 tbi/th400/np241c
Yeah the knock has always been there but it was worse when the timing was advanced,,,,I couldnt get it to knock today but ill know for sure if its gone after i drive it for a while,,,,i thought it could be carbon build up maybe cuz of the gear ratio its always revving higher that it was intended,,,i dont know if higher rpms would cause more carbon or less build up though,,,,i did try diff gas for a while including higher octane but there was no change,,,it would knock with super in it as well,,,,
 

Jims86

Full Access Member
Joined
Aug 3, 2010
Posts
5,492
Reaction score
135
Location
Patterson,Ca
First Name
Jim
Truck Year
1986
Truck Model
K10 Suburban Silverado
Engine Size
5.7 TBI
Yeah the knock has always been there but it was worse when the timing was advanced,,,,I couldnt get it to knock today but ill know for sure if its gone after i drive it for a while,,,,i thought it could be carbon build up maybe cuz of the gear ratio its always revving higher that it was intended,,,i dont know if higher rpms would cause more carbon or less build up though,,,,i did try diff gas for a while including higher octane but there was no change,,,it would knock with super in it as well,,,,

Yeah, well $10 for a can of seafoam, and it can be introduced through the throttle body...just foller the directions on the can, then let it sit for 20 minutes. It will smoke like a sunuvabitch when you fire it back up, but may help some.
 

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,132
Reaction score
9,331
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
IIRC, EGR failure and Carbon build up DO NOT cause knock. Carbon build up can be caused by knock, pre-ignition or detonation though.
 

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,132
Reaction score
9,331
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
Yeah, well $10 for a can of seafoam, and it can be introduced through the throttle body...just foller the directions on the can, then let it sit for 20 minutes. It will smoke like a sunuvabitch when you fire it back up, but may help some.

The directions will say 1/3 of the can up a vac line and let it sit for 15-20, 1/3 in the crankcase, and 1/3 in the fuel tank. I've done half in the fuel tank, 1/2 up the vac line with good results. 1/3 may have worked too but I did half cans. Then I commonly do 1/2 can fuel tank, 1/2 can crankcase and don't do the sitting on the pistons. Keep the motor clean, you shouldn't have carbon build up and what little you will get, can get cleaned off through your fuel tank and driving it.
 

Jims86

Full Access Member
Joined
Aug 3, 2010
Posts
5,492
Reaction score
135
Location
Patterson,Ca
First Name
Jim
Truck Year
1986
Truck Model
K10 Suburban Silverado
Engine Size
5.7 TBI
IIRC, EGR failure and Carbon build up DO NOT cause knock. Carbon build up can be caused by knock, pre-ignition or detonation though.

Carbon build up in the cylinders is what I is preachin...which could also be exaserbated by a weak or misfiring aftermarket coil.
 

HotRodPC

Administrator
Staff member
Admin
Joined
Aug 29, 2010
Posts
47,132
Reaction score
9,331
Location
OKC, OK
First Name
HotRod
Truck Year
85 K20 LWB
Truck Model
Silverado
Engine Size
454 - Turbo 400 - 3.73
Carbon build up in the cylinders is what I is preachin...which could also be exaserbated by a weak or misfiring aftermarket coil.

I'll agree, the coil was PROBABLY the main source of the problem. MSD's are NOT POS's, it's just that HEI knows what it likes and neither MSD or Mallory either one of the Red guys are liked by HEI. I'm not certain on Accel though. I'm pretty sure I know of 2 guys running Accel, Coil, Cap, Rotor and Wires and they run good. Like stock, nothing impressive. Could done the same with OE parts.
 

Jims86

Full Access Member
Joined
Aug 3, 2010
Posts
5,492
Reaction score
135
Location
Patterson,Ca
First Name
Jim
Truck Year
1986
Truck Model
K10 Suburban Silverado
Engine Size
5.7 TBI
I'll agree, the coil was PROBABLY the main source of the problem. MSD's are NOT POS's, it's just that HEI knows what it likes and neither MSD or Mallory either one of the Red guys are liked by HEI. I'm not certain on Accel though. I'm pretty sure I know of 2 guys running Accel, Coil, Cap, Rotor and Wires and they run good. Like stock, nothing impressive. Could done the same with OE parts.

I had the big accel HEI coil. nver had a problem, but my engine didnt really warrent its use either. Jacobs is the **** too...I had the full RV system.
 

Forum statistics

Threads
44,560
Posts
960,969
Members
37,041
Latest member
Aardvark1024
Top