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Started By
Message
OB mechanics, 4x4 help needed
Posted on 9/29/13 at 7:53 pm
Posted on 9/29/13 at 7:53 pm
I have a '98 chevy that came with a 305 which I later had the dealership change out to a 350 then set the computer for 350. '98 305 has three O-2 sensors and the 350 has four so my computer isn't receiving a reading from the fourth sensor and gives the infamous check engine light preventing me from getting an inspection sticker. I know all the tricks for getting a tag but I want to get this fixed so it's legit. TIA
5
Posted on 9/29/13 at 7:55 pm to 007mag
Not sure if possible? 2 pre and 2 post catalytic converter correct? If so it's about that not the engine.
Posted on 9/29/13 at 8:04 pm to 007mag
Go to a junkyard and get a computer from a 350 truck.
Posted on 9/29/13 at 8:12 pm to 2indapink
Correct the 305 model had 2 before a single converter and one after. The 350 had two before dual converters and 2 after. I think I need to have someone program the computer because I am missing a sensor and the wiring for the sensor.
Posted on 9/29/13 at 8:16 pm to 007mag
Install a 4th sensor and wire for it, or just the wiring and hook 2 sets of wires to the 3rd sensor.
Posted on 9/29/13 at 8:21 pm to shawnlsu
quote:Is this possible? Would I just solder the wires into empty port on th harness plug or is it a different plug at the computer?
hook 2 sets of wires to the 3rd sensor
Posted on 9/29/13 at 8:31 pm to 007mag
I'm not sure if it works like that. If it reads off of resistance (which I think it does) it's going to F with it.
You're probably going to have to re-flash the computer to a 350 program.
Scrapping a computer is iffy because of the bazillion different ways they can be programmed from the factory.
I'd do some digging on fullsizechevy.com and see what they have to say. I know somebody who had the same issue with a 305 swapped to 350. He got the computer re-flashed and it was fine afterwards. I think his was a 96 though so it might be different.
You're probably going to have to re-flash the computer to a 350 program.
Scrapping a computer is iffy because of the bazillion different ways they can be programmed from the factory.
I'd do some digging on fullsizechevy.com and see what they have to say. I know somebody who had the same issue with a 305 swapped to 350. He got the computer re-flashed and it was fine afterwards. I think his was a 96 though so it might be different.
Posted on 9/29/13 at 8:34 pm to 007mag
So are you saying the computer is expecting input from a fourth sensor, but there is no place to wire it in?? If this is not the case I don't see a computer can give an error code for a sensor it doesn't know exists.
Posted on 9/29/13 at 8:45 pm to skidry
quote:I think that's what they did.
computer re-flashed
quote:The computer thinks it is a 350 computer and monitoring a 350 exhaust system with two convertors but my exhaust is the original 305 exhaust with only one convertor. I'm not sure if there is or isn't a place to add wires for the missing sensor in the current harness connection.
So are you saying the computer is expecting input from a fourth sensor, but there is no place to wire it in
Posted on 9/29/13 at 8:48 pm to 007mag
Look on fullsizechevy.com and seach 305 to 350 SPFI swap. Somebody's done it and knows how to deal with it.
Posted on 9/29/13 at 8:48 pm to DownshiftAndFloorIt
will do thanks
Posted on 9/29/13 at 9:04 pm to 007mag
I honestly would go to the dealer and get their opinion on a solution. If they swapped the engine, they should have done the flash over program on the existing computer to prevent the issue.
Posted on 9/29/13 at 9:30 pm to 007mag
Put the check engine light on a toggle switch. Aint a 4x4 without at least one toggle!
Posted on 9/29/13 at 9:33 pm to TIGER2
quote:
Put the check engine light on a toggle switch
That don't work on the new stuff man. They check it with a computer
Posted on 9/29/13 at 9:39 pm to DownshiftAndFloorIt
In Louisiana? That must be city shite! No computer check in Mandeville.
Posted on 9/29/13 at 9:40 pm to TIGER2
Everytime I bring mine they don't check shite because they think it's carburated
But when I had my 98 chevy, it always got plugged in for inspection stickers, and almost every time it failed
But when I had my 98 chevy, it always got plugged in for inspection stickers, and almost every time it failed
Posted on 9/30/13 at 7:24 am to DownshiftAndFloorIt
Just have someone reflash with a laptop.
They can turn of that circuit.
Had it done a few times.
They can turn of that circuit.
Had it done a few times.
Posted on 9/30/13 at 7:43 am to greasemonkey
quote:
Just have someone reflash with a laptop
Are you familiar with the programs to do this? I've always wanted to get a program and extra ECU for my truck to play with.
Posted on 9/30/13 at 8:51 am to TIGER2
Actually it's the 5 parish area around Baton Rouge that requires the emission checks, thing. 
quote:This sounds like what I'm wanting done. Anyone know who does this in Baton Rouge area?
Just have someone reflash with a laptop. They can turn off that circuit.
Posted on 9/30/13 at 10:48 am to DownshiftAndFloorIt
quote:
Are you familiar with the programs to do this? I've always wanted to get a program and extra ECU for my truck to play with.
If yours is 96 or newer, then its worth doing.
Gave my 97 tahoe huntin buggy more power and mpg if driven right.
The tranny setup is where you get most gains with bigger tires. Get them to make the converter lock in 4th gear only, will make tranny last longer.
Chevy locks the converter in 2nd and it lugs down the motor,hurting mpgs
I believe the program for the laptop is called hp 2000.
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