Vince's TBI woes, progressive revelations, and tbi mods.

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.

Vbb199

B-rate Hillbilly Customs
Joined
Jan 12, 2018
Posts
8,871
Reaction score
14,885
Location
Salisbury NC
First Name
Vince
Truck Year
89, 79
Truck Model
89 Suburban R1500, 79 C10
Engine Size
350, 502
o_O

Them F bodys are SUPER PICKY about their knock sensors- word?

When dude said his engine is 10.5:1 ? that was a clue, Blue.


Youre spot on.
Didnt even think about more....
Volatile? Conditions since its colder

Cold air make engine go boom boom harder


Gonna give it a go tomorrow.....been working....


No work tomorrow!
Will also be checking dizzy to see if its a wore out biatch
 

Rusty Nail

Full Access Member
Joined
Jan 29, 2015
Posts
9,734
Reaction score
9,531
Location
the other side of the internet
First Name
Rusty
Truck Year
1977
Truck Model
C20
Engine Size
350sbc
Maybe some genius will elaborate the difference (s) between winter and summer fuels. :shrug:
Surely consideration is given to richer mixtures (i.e. "choke" operations, etc. - If I knew id say.

I really liked the weak coil under max load idea too. That happens for sure. AND it's hard to diagnose..
 

Vbb199

B-rate Hillbilly Customs
Joined
Jan 12, 2018
Posts
8,871
Reaction score
14,885
Location
Salisbury NC
First Name
Vince
Truck Year
89, 79
Truck Model
89 Suburban R1500, 79 C10
Engine Size
350, 502
Maybe some genius will elaborate the difference (s) between winter and summer fuels. :shrug:
Surely consideration is given to richer mixtures (i.e. "choke" operations, etc. - If I knew id say.

I really liked the weak coil under max load idea too. That happens for sure. AND it's hard to diagnose..

Dizzy is getting replaced no matter what.
It was on my agenda for upgrades.
As well as coil.
Its already ordered and will arrive tuesday
 

1987 GMC Jimmy

Automobile Hoarder
Joined
Jan 23, 2016
Posts
5,848
Reaction score
2,387
Location
Mississippi
First Name
Jesse
Truck Year
1987
Truck Model
V1500 Jimmy
Engine Size
350
Ahh, there’s my soapbox. So if you had a scan tool and looked at the serial data in real time, you could watch the knock counts and see if it’s going crazy or not so much. Ideally, it’ll knock a couple times at startup, figure it out after a few seconds, and adjust accordingly. The self-test comes a little later as you’ve experienced.

It may have one or two once in a while, but if it’s doing it pretty constantly, you could run with that. Obviously, that’s after your distributor is nice and tight. You’d then have to adjust timing back or mute the knock sensor as suggested. I don’t know about them being overly sensitive, but I’m not doubting it. Still, though. You’re running 91 octane, which should be fine for a 10.5:1 engine even with a respectable base setting. Maybe it’s time to upgrade to 100LL Avgas.
 

Vbb199

B-rate Hillbilly Customs
Joined
Jan 12, 2018
Posts
8,871
Reaction score
14,885
Location
Salisbury NC
First Name
Vince
Truck Year
89, 79
Truck Model
89 Suburban R1500, 79 C10
Engine Size
350, 502
Ahh, there’s my soapbox. So if you had a scan tool and looked at the serial data in real time, you could watch the knock counts and see if it’s going crazy or not so much. Ideally, it’ll knock a couple times at startup, figure it out after a few seconds, and adjust accordingly. The self-test comes a little later as you’ve experienced.

It may have one or two once in a while, but if it’s doing it pretty constantly, you could run with that. Obviously, that’s after your distributor is nice and tight. You’d then have to adjust timing back or mute the knock sensor as suggested. I don’t know about them being overly sensitive, but I’m not doubting it. Still, though. You’re running 91 octane, which should be fine for a 10.5:1 engine even with a respectable base setting. Maybe it’s time to upgrade to 100LL Avgas.


My personal opinion, while ******* with the knock sensor is a good idea and probably 40%of the problem, i think its just masking a deeper issue, the worn out dist.

The issue is rapidly getting worse, and so is the power, Im having random misses on cold cranking now,

the knock sensor would set 1 standard condition, and that be what it is. The decrease in power wouldnt worsen

When the engine temp is still below the thermostat opening , while i dont peg the go fast pedal, i feel the power.

The problems only really show up once its at operating temp and ive been driving it for a bit.


Imo, its......STILL.....a 33x,*** distributor from 1989 with worn out bearings.
Timing IS advanced a couple degrees.

Its evident when i pull a load behind the truck , it (used to) spark knock under WOT.

New dist will get a safer adjusted timing


By the way, as far as the sensitivity, hold a timing light on the dampener and have a buddy lightly tap the block with a hammer (LIGHTLY), if the knock sensor is working correctly, itll pick it up and retard timing.
 
Last edited:

1987 GMC Jimmy

Automobile Hoarder
Joined
Jan 23, 2016
Posts
5,848
Reaction score
2,387
Location
Mississippi
First Name
Jesse
Truck Year
1987
Truck Model
V1500 Jimmy
Engine Size
350
I agree, distributor is public enemy number one at this point. Anything else is just kinda riding the coattails of that.
 

Vbb199

B-rate Hillbilly Customs
Joined
Jan 12, 2018
Posts
8,871
Reaction score
14,885
Location
Salisbury NC
First Name
Vince
Truck Year
89, 79
Truck Model
89 Suburban R1500, 79 C10
Engine Size
350, 502
Maybe some genius will elaborate the difference (s) between winter and summer fuels. :shrug:
Surely consideration is given to richer mixtures (i.e. "choke" operations, etc. - If I knew id say.

I really liked the weak coil under max load idea too. That happens for sure. AND it's hard to diagnose..


I failed to add, i would imagine ^this^ gets into MAP readings, with density of air at different ambient temps outdoors.

Those map readings changes the AFR to probably a richer condition (If i had to guess)


I might be wrong, i just know a MAP is what sets the difference in a carb and a basic tbi.... no need for rejetting at different sea levels thanks to MAP.
 

Vbb199

B-rate Hillbilly Customs
Joined
Jan 12, 2018
Posts
8,871
Reaction score
14,885
Location
Salisbury NC
First Name
Vince
Truck Year
89, 79
Truck Model
89 Suburban R1500, 79 C10
Engine Size
350, 502
Okays..... so theres this


xc_hide_links_from_guests_guests_error_hide_media


Pretty sloppy.

ALSO! I remembered i already own a igintion box and super coil to go with it, direct plug and play in the tbi.


I FINALLY got tracking for my prom chip as well.....
(I was getting suspicious)

After new dizzy, prom, ignition box + regap..... betcha she'll be a nasty mf
 

shiftpro

Full Access Member
Joined
Aug 31, 2012
Posts
4,855
Reaction score
6,085
Location
BC Canada
First Name
shiftpro
Truck Year
73-87
Truck Model
1500, 2500, 3500
Engine Size
350, 383, 454, 496!
I just thought of another dizzy issue... I went through this last spring.
The power lead that plugs in to the dizzy... well it was really worn out and very loose. My power to the dizzy was there but some shorting and weak connection would result in hard starting... until it didn't start anymore. I cleaned and pulled the contacts out a bit (inside the plug, power side) and I was rolling again.
Just another experience to share here. Just because there is power at the lead don't assume it's feeding the dizzy it's full uninterrupted voltage.
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,121
Reaction score
6,038
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
does your truck show live data? Im not sure if your crate uses factory HEI or whatever.
what im saying, is, if you have obd 1 interface and a way to read data, have you checked your computers ignition advance according to computer? Like, tech 1 or tech 2, how much advance in degrees or retard (negative advance) my uncles 95 van allowed me to see what the computer said/thought. I wanna say off-the-line it was sluggish but it was perfect in the high end, his advance while cruising was 12-22 degrees unadjusted according to the computer.

if you have any other gm vehicles post 1991 and pre 2014 i highly recommend a tech 2
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,121
Reaction score
6,038
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Wanna see the ignition coil on my f150? or the old coil pack for my park avenue? they would give your cap a run for its money lol

Oh the worst was the ignition coil bolts for my old saturn sw2
 

Vbb199

B-rate Hillbilly Customs
Joined
Jan 12, 2018
Posts
8,871
Reaction score
14,885
Location
Salisbury NC
First Name
Vince
Truck Year
89, 79
Truck Model
89 Suburban R1500, 79 C10
Engine Size
350, 502
does your truck show live data? Im not sure if your crate uses factory HEI or whatever.
what im saying, is, if you have obd 1 interface and a way to read data, have you checked your computers ignition advance according to computer? Like, tech 1 or tech 2, how much advance in degrees or retard (negative advance) my uncles 95 van allowed me to see what the computer said/thought. I wanna say off-the-line it was sluggish but it was perfect in the high end, his advance while cruising was 12-22 degrees unadjusted according to the computer.

if you have any other gm vehicles post 1991 and pre 2014 i highly recommend a tech 2


It uses computer controlled advance.

Theres no weights or vac advance.
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,121
Reaction score
6,038
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
It uses computer controlled advance.

Theres no weights or vac advance.
no what im saying is, can you check what the computer is saying the advance is? then confirm it with a timing light? if a computer cant understand the what is it makes a terrible job at winging it as far as early computers in cars go
 

Vbb199

B-rate Hillbilly Customs
Joined
Jan 12, 2018
Posts
8,871
Reaction score
14,885
Location
Salisbury NC
First Name
Vince
Truck Year
89, 79
Truck Model
89 Suburban R1500, 79 C10
Engine Size
350, 502

Forum statistics

Threads
41,852
Posts
903,520
Members
33,365
Latest member
rossivey
Top