Spark plug foul up

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.

M

martingmc86

Member
Joined
Dec 10, 2022
Posts
45
Reaction score
4
Location
california
First Name
martin
Truck Year
86
Truck Model
gmc sierra 1500
Engine Size
v8 5.0
I have an 86 GMC Sierra 5.0 with a MSD atomic 1 EFI have had an issue with my spark plugs, getting folded up after a couple hundred miles to get cover in black and truck runs like **** first, I thought it was my carburetor so I decided to swap it out to an MSD atomic one EFI and it runs great but after a couple hundred miles like I’ve said the spark plugs foul and goes back to **** what can it be? I rebuild the distributor and put new pick up coil new capacitor, spark plug module new rotor plugs and new cables and still does the same thing my distributor does not have a vacuum advance it is a ESC ELECTRONIC SPARK CONTROL came out of California, so it had smog regulations
 
R

Robert Bare

Full Access Member
Joined
Sep 13, 2020
Posts
107
Reaction score
161
Location
MT
First Name
Robert
Truck Year
1978
Truck Model
k20
Engine Size
5.7
First you have to determine if it is too much oil or gas. Plenty of youtube vids can help you.
 
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,591
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
See if your timing actually advances,no advance will foul plugs. Monitor O2 sensor voltage with a multimeter,postcresults. O2 sensor has to be hot to work so monitor hot.
 
M

martingmc86

Member
Joined
Dec 10, 2022
Posts
45
Reaction score
4
Location
california
First Name
martin
Truck Year
86
Truck Model
gmc sierra 1500
Engine Size
v8 5.0
Ricko1966 said:
See if your timing actually advances,no advance will foul plugs. Monitor O2 sensor voltage with a multimeter,postcresults. O2 sensor has to be hot to work so monitor hot.
Click to expand...
Ok it’s a single wire o2 sensor so I’m guessing positive to wire and ground to ground and should I be shecking volt or ohms
 
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,591
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
martingmc86 said:
Ok it’s a single wire o2 sensor so I’m guessing positive to wire and ground to ground and should I be shecking volt or ohms
Click to expand...
Positive lead lead of a meter to single wire on O2 sensor ground lead of meter to ground,looking for volts .1 is lean .5 is stoich .9 is rich. you can run a wire into the car so you can monitor daily as you drive. Piggy back your wire at the O2 meaning leave it in the system just monitor it.Didnt you have something going on where you need 2x O2 sensors. 1 for OE computer 1 fir aftermarket EFI ?
 
M

martingmc86

Member
Joined
Dec 10, 2022
Posts
45
Reaction score
4
Location
california
First Name
martin
Truck Year
86
Truck Model
gmc sierra 1500
Engine Size
v8 5.0
Ricko1966 said:
Positive lead lead of a meter to single wire on O2 sensor ground lead of meter to ground,looking for volts .1 is lean .5 is stoich .9 is rich. you can run a wire into the car so you can monitor daily as you drive. Piggy back your wire at the O2 meaning leave it in the system just monitor it.Didnt you have something going on where you need 2x O2 sensors. 1 for OE computer 1 fir aftermarket EFI ?
Click to expand...
Yes, that is correct. I have two oxygen sensors one is for my EFI and one is for my trucks ESC I added back my original oxygen sensor and didn’t notice a difference thing that sucks right now is that my truck runs like **** but if I clean or put new spark plugs run it will a couple hundred miles really good then my spark plugs foul up and goes back to running bad and my truck runs like **** again lol
 
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,591
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Monitor the o2 sensor voltage,post back
 
Y

YakkoWarner

Full Access Member
Joined
May 29, 2024
Posts
161
Reaction score
184
Location
Central Texas
First Name
Wolf
Truck Year
1989
Truck Model
R2500 Suburban
Engine Size
454
Ricko1966 said:
Positive lead lead of a meter to single wire on O2 sensor ground lead of meter to ground,looking for volts .1 is lean .5 is stoich .9 is rich. you can run a wire into the car so you can monitor daily as you drive. Piggy back your wire at the O2 meaning leave it in the system just monitor it.Didnt you have something going on where you need 2x O2 sensors. 1 for OE computer 1 fir aftermarket EFI ?
Click to expand...

Question on this: Does the O2 sensor generate the voltage (using a thermocouple-type device) or does the ECU provide a specific voltage to the wire going to the O2 sensor (voltage changes based on resistance inside the sensor)? Doesn't change the way the voltage is monitored, just wondering what the actual process is.
 
R

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,385
Reaction score
8,591
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
YakkoWarner said:
Question on this: Does the O2 sensor generate the voltage (using a thermocouple-type device) or does the ECU provide a specific voltage to the wire going to the O2 sensor (voltage changes based on resistance inside the sensor)? Doesn't change the way the voltage is monitored, just wondering what the actual process is.
Click to expand...
O2 sensor produces voltage. That's what the ecu reads it evaluates the voltage and determines add or subtract fuel
 
J

JBswth

Full Access Member
Joined
Jan 24, 2022
Posts
215
Reaction score
177
Location
Vallejo, California
First Name
James
Truck Year
1973
Truck Model
C25
Engine Size
292 cubic inches
martingmc86 said:
I have an 86 GMC Sierra 5.0 with a MSD atomic 1 EFI have had an issue with my spark plugs, getting folded up after a couple hundred miles to get cover in black and truck runs like **** first, I thought it was my carburetor so I decided to swap it out to an MSD atomic one EFI and it runs great but after a couple hundred miles like I’ve said the spark plugs foul and goes back to **** what can it be? I rebuild the distributor and put new pick up coil new capacitor, spark plug module new rotor plugs and new cables and still does the same thing my distributor does not have a vacuum advance it is a ESC ELECTRONIC SPARK CONTROL came out of California, so it had smog regulations
Click to expand...
Sounds like either bad rings or bad valve guides with missing seals. Maybe both. You can try one heat range hotter, that might do the trick until you rebuild the engine.

J. B.

J. B.
 
G

gmbellew

Full Access Member
Joined
May 27, 2018
Posts
1,211
Reaction score
1,278
Location
Kansas city
First Name
glen
Truck Year
1990
Truck Model
suburban 1500
Engine Size
350
martingmc86 said:
Ok so I got some readings at idle.41 and at 25mph I got a reading of .73
Click to expand...

O2 voltage should be constantly varying back and forth between 0.1v and 0.9v as the computer constantly adjusts fuel. high volts is rich and it pulls fuel (fuel trims will be below 128). low voltage is lean and it adds fuel (fuel trims will be above 128). ideal AFR is around 0.5v, but it will never sit around 0.5v for long.

are you having oil consumption?

might post some pics of the plugs after theys are fouled.
 
M

martingmc86

Member
Joined
Dec 10, 2022
Posts
45
Reaction score
4
Location
california
First Name
martin
Truck Year
86
Truck Model
gmc sierra 1500
Engine Size
v8 5.0
gmbellew said:
O2 voltage should be constantly varying back and forth between 0.1v and 0.9v as the computer constantly adjusts fuel. high volts is rich and it pulls fuel (fuel trims will be below 128). low voltage is lean and it adds fuel (fuel trims will be above 128). ideal AFR is around 0.5v, but it will never sit around 0.5v for long.

are you having oil consumption?

might post some pics of the plugs after theys are fouled.
Click to expand...
My bad the reading was .4 at idle and .6 at 30 mph
 
M

martingmc86

Member
Joined
Dec 10, 2022
Posts
45
Reaction score
4
Location
california
First Name
martin
Truck Year
86
Truck Model
gmc sierra 1500
Engine Size
v8 5.0
gmbellew said:
O2 voltage should be constantly varying back and forth between 0.1v and 0.9v as the computer constantly adjusts fuel. high volts is rich and it pulls fuel (fuel trims will be below 128). low voltage is lean and it adds fuel (fuel trims will be above 128). ideal AFR is around 0.5v, but it will never sit around 0.5v for long.

are you having oil consumption?

might post some pics of the plugs after theys are fouled.
Click to expand...
Yes I’ll post pics in a bit
 
You must log in or register to reply here.

Similar threads

granthendrickson
Spark plug
Replies
9
Views
598
AuroraGirl
AuroraGirl
labbetheking
383 stroker which spark plugs?
Replies
9
Views
648
Grit dog
Grit dog
M
ESC module
Replies
2
Views
308
squaredeal91
squaredeal91
beady
Thoughts on how to recover from a slightly cross threaded spark plug threads in head?
Replies
13
Views
736
beady
beady
Knep115
86 HEI no spark
2 3
Replies
31
Views
2K
Rustisbest
Rustisbest

Latest posts

Forum statistics

Threads
44,083
Posts
949,039
Members
36,162
Latest member
jbahena95
Top