1994 TBI 350 Stretched Timing Chain

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.

megafan0258

Newbie
Joined
Feb 21, 2022
Messages
25
Reaction score
38
Location
Ohio
That means you're running lean. It takes time to level off IF you have enough fuel pressure and everything else is good, like your O2 sensor.
Thats what I was assuming from what I read but wanted to confirm.

Fuel pump was replaced with a Delphi unit and pressure was good but I havent check for volume.

It has a BLM of 135 on start up and went in and out of closed loop a couple of time after about 160 degrees.

Also does the computer take 02 into account in open loop? If not then I would assume I have a fuel delivery issue.

What are normal values to have in closed loop for a TBI 350?

Thank You for the response.
 

Schurkey

Supporting Member
Supporting Member
Joined
Jan 14, 2018
Messages
12,640
Reaction score
16,487
Location
The Seasonally Frozen Wastelands
Does the battery need disconnected (to reset computer) after messing with the initial timing to reset timing curve? Or is that not a thing?
You missed the "to be" in between "need" and "disconnected".

And I have heard that disconnecting the battery--which erases all the volatile memory in the computer--can make a sudden, dramatic improvement in vehicle performance.

I worked on a Ford Focus about a month ago that ran horribly, and got 80+ percent "fixed" by deliberately giving the computer amnesia. The remaining 20% is still bugging me.


The eBay junk I bought is the injector coil balancer tester, selector switch box, and the 4.3 harness. I was surprised at how relatively cheap it all was. I plan to keep this truck for a number of years so I like having the diagnostic tools available.
Yup. If you have the tool, you probably want to get additional harnesses so you can use it on additional vehicles. In a perfect world, you'd pay for that tool plus some extra--or become a local hero--by performing diagnostic time on other's vehicles.

No but, you need to disconnect the battery to reset the EST fault you get from disconnecting the BLK/TAN wire.
It does that, too.

Clears volatile memory
Clears codes
 
Last edited:

PlayingWithTBI

2022 Truck of the Year
Supporting Member
Joined
Jan 3, 2019
Messages
10,426
Reaction score
16,881
Location
Tonopah, AZ
It does that, too.

Clears volatile memory
Clears codes
The question was;
Does the battery need disconnected (to reset computer) after messing with the initial timing to reset timing curve? Or is that not a thing?
yes, resetting the volatile memory will reset INT and BLM values but, it will not "reset timing curves". FWIU the fine tuning of VE is done based on MAP and RPM (but the table is not changed) with feedback from the O2 sensor while in CL, the SA tables are static and don't get "adjusted" in volatile memory. Other changes to timing from the ICM, as an example, are physical or hardware adjusted.

I guess I could have been more elaborate on that;
Over time the INT and BLM will be adjusted but, resetting the computer will return it to the original state where it runs directly off VE and SA tables, then will fine tune AFR as close as it can to 128 (in this case) based on those tables. If the tables are so far off, like when a cam or other performance changes have been made, the INT and BLM can change it only so far. That's why it needs "tuning" to run properly.

Does that make any sense?
 

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
7,237
Reaction score
10,079
Location
DFW, TX
I had an odd ignition timing situation on my 1995 S10 Blazer, which I chased for years.

Read the story here, about how the reluctor wheel on the distributor shaft crept SLOWLY over time (years):

https://www.gmt400.com/threads/1993-chevy-c1500-4-3-power-issues.62069/post-1313440
Surprised it had a TBI style distributor. Mine had a Vortec style spider cap and a crank sensor on it with a black box PCM. Brother also had a 1995 TBI S10 with the same setup on it.
 

1998_K1500_Sub

Nitro Junkie
Supporting Member
Joined
Jan 28, 2019
Messages
2,899
Reaction score
4,545
Location
Rural Illinois
Surprised it had a TBI style distributor. Mine had a Vortec style spider cap and a crank sensor on it with a black box PCM. Brother also had a 1995 TBI S10 with the same setup on it.

Sounds like yours was the OBD1.5, yes? I once owned a 1995 S10 4.3L VIN Z manual ECSB with that setup.

My 1995 VIN W S10 Blazer was OBD1.0, 8-bit ECU in the cab. A friend now owns it.

I also have a 1995 S10 4.3L VIN Z RCLB OBD1.0, 8-bit ECU; I later stuffed an L31 crate into it and still drive it from time to time.
 
Last edited:

L31MaxExpress

I'm Awesome
Joined
Apr 21, 2018
Messages
7,237
Reaction score
10,079
Location
DFW, TX
Sounds like yours was the OBD1.5, yes? I once owned a 1995 S10 4.3L VIN Z manual ECSB with that setup.

My 1995 VIN W S10 Blazer was OBD1.0, 8-bit ECU in the cab. A friend now owns it.

I also have a 1995 S10 4.3L VIN Z RCLB OBD1.0, 8-bit ECU; I later stuffed an L31 crate into it and still drive it from time to time.
Yes it was an OBD1.5. I have seen 94s with OBD 1.5. Thought all 95s were myself, just news to me there were actually regular OBD1 S10s in 95.
 
Top