Hello everyone, new guy here. I was referred here to hopefully get some help trying to figure out some issues with my 16 year olds newly purchased truck.
Long story short...someone in the trucks past life had swapped in a built vortec 350, with a GMPP vortec TBI intake, headers/duals, cam, etc. It ran ok, but the engine ended up being in need of a total rebuild...I'll leave out all the gory details, but lets just say a valvetrain "noise" snowballed into an engine swap.
We swapped the trashed engine with the bone stock L31 vortec engine out of my old '99 Suburban 3/4 ton. Used the vortec TBI intake and TBI unit, and headers/exhaust...otherwise it is still a stock '99 vortec 350 long block.
The engine is in and running...starts right up and idles at 675 rpm perfectly fine. Transitional throttle response is pretty bad though...it acts quite lean, and the spark plugs confirm this. It stumbles on light throttle tip in and lightly pops out the exhaust.
I have a Bosch OBD1300 scan tool that I have used on many vehicles over the years, and never had any issues with it, until now with this truck. This thing is OBD1, and my scan tool does not see the ECM. I have an old DLC plug in device for GM OBD1 vehicles that is supposed to make it flash any trouble codes...it also does nothing. And jumpering between the A and B ALDL posts does nothing either. There is no "check engine" light, but there is a "check gages" light that is always on and never changes or flashes.
I have been troubleshooting this for several days now, but I'm not getting anywhere. Here are the pinouts of the ALDL connector and what I am seeing with the key on, engine off...
Position A...0 ohms to ground
B...5.05 volts
C...0 volts
D, E, and F not used
G...0 volts
H...9.68 volts. I believe this goes to the ABS system
J...0 volts
K and L not used
M...5.01 volts. I believe this one is supposed to be the data stream.
I have no idea what, if anything, has been done to the computer in this thing. There is no EGR. With the timing set at 0 with the spout connector disconnected, it idles at 16* timing with the spout connector plugged in, but hits maximum timing of 22* by 1000 rpms and doesn't advance any further. It very well may be a stock TBI computer and chip. Maybe it's in some sort of limp mode? The computer is a 16196395 unit, BJLJ.
Where do I go from here? I'd like to at least be able to see the data stream and check O2 sensor function, fuel trims, etc. Could it simply be the computer is bad?
Long story short...someone in the trucks past life had swapped in a built vortec 350, with a GMPP vortec TBI intake, headers/duals, cam, etc. It ran ok, but the engine ended up being in need of a total rebuild...I'll leave out all the gory details, but lets just say a valvetrain "noise" snowballed into an engine swap.
We swapped the trashed engine with the bone stock L31 vortec engine out of my old '99 Suburban 3/4 ton. Used the vortec TBI intake and TBI unit, and headers/exhaust...otherwise it is still a stock '99 vortec 350 long block.
The engine is in and running...starts right up and idles at 675 rpm perfectly fine. Transitional throttle response is pretty bad though...it acts quite lean, and the spark plugs confirm this. It stumbles on light throttle tip in and lightly pops out the exhaust.
I have a Bosch OBD1300 scan tool that I have used on many vehicles over the years, and never had any issues with it, until now with this truck. This thing is OBD1, and my scan tool does not see the ECM. I have an old DLC plug in device for GM OBD1 vehicles that is supposed to make it flash any trouble codes...it also does nothing. And jumpering between the A and B ALDL posts does nothing either. There is no "check engine" light, but there is a "check gages" light that is always on and never changes or flashes.
I have been troubleshooting this for several days now, but I'm not getting anywhere. Here are the pinouts of the ALDL connector and what I am seeing with the key on, engine off...
Position A...0 ohms to ground
B...5.05 volts
C...0 volts
D, E, and F not used
G...0 volts
H...9.68 volts. I believe this goes to the ABS system
J...0 volts
K and L not used
M...5.01 volts. I believe this one is supposed to be the data stream.
I have no idea what, if anything, has been done to the computer in this thing. There is no EGR. With the timing set at 0 with the spout connector disconnected, it idles at 16* timing with the spout connector plugged in, but hits maximum timing of 22* by 1000 rpms and doesn't advance any further. It very well may be a stock TBI computer and chip. Maybe it's in some sort of limp mode? The computer is a 16196395 unit, BJLJ.
Where do I go from here? I'd like to at least be able to see the data stream and check O2 sensor function, fuel trims, etc. Could it simply be the computer is bad?