I am currently putting a TBI unit off a 1995 Chevy pickup with a 5.7 L engine on to a 1974 Chevy pickup with 5.7 L engine and have some questions about VSS and EGR. If anyone has done something like this, I would really like to hear from you.
Thx a lot
Dan Brown
TBI computers use a 2000 pulses per mile VSS square wave signal.
https://jagsthatrun.com/collections/...ce-holder-4pac
The original 95 Chevy used a Vehicle Speed Sensor Buffer (VSSB) for the 95 Chevy dash speedometer and ABS braking system. The VSSB is not needed for the 74 Chevy if your using a TH400, TH350, or manual transmission. The 95 Chevy VSSB is needed if your going to use a 4L60E, 4L80E, or 700R4. If you have a 4L60E, 4L80E or 700R4 you should a VSS in the transmission, eliminating the need for the JTR aftermarket VSS. ****Some 700R4 transmissions Do Not Have a VSS.*****
Direction are supplied with the VSS or contact JTR tech support.
The EGR can be disabled in the chip programming by setting EGR "ON" at 151 degrees Celsius (304 Fahrenheit) and / or EGR "ON" at 255 MPH.
dave w
Don't forget the Park/Neutral input to the ECM. Painless makes a simple relay kit that uses the OEM park/neutral switch and provides both the correct signal for the ECM and Park/Neutral startup protection. Their kit is easy to duplicate with a relay and a diode as well.Originally Posted by Dan Brown
The 1995 16197427 Second Generation TBI computer does not have a Park / Neutral input wire like the older 1227747 First Generation TBI computer does.
I agree 100%, a Park / Neutral safety switch is a must have feature!
dave w
Last edited by dave w; 01-28-2020 at 01:37 AM.
I am using a Muncie SM465 which is a manual transmission, so, if I'm reading dave w right, I don't need a VSS. If this is correct, and I don't use one, will I have any driving problems? Too, as for the EGR, how do I handle that? I didn't bother to worry about an EGR valve when I started this project since the vehicle is over 40 years old and in Texas, it's exempt from any emissions check, but I'm now being told that if I don't use one, the MIL will be on constantly since the ECM isn't seeing an EGR signal. True/False?
You will want a VSS. You will not get away without tuning the ECM unless you run a factory 350 cam and factory TBI heads.
I actually just took off my jags that run 2000 pulse per mile vss sensor since i switched to the 4l60e and got their 40 pulse per revolution reluctor kit. PM and I'll send the 2000 ppm for $75 shipped.
What is the computer part number your using for the TBI conversion?
dave w
It does too!!! It uses one of the pressure sensor inputs from the E-Trans when it is in TCC only mode. It is in my wiring change chart.
The manual trans trucks use a clutch anticipate switch from what I remember too.
I can't find 16197427 wiring schematic showing a wire labeled Park / Neutral. Please post a 16197427 wiring schematic showing the Park / Neutral wire.
dave w
Had to reference my old writeup on TGO. When you have TCC only option selected if you input the Park/Neutral wire into pin E5 the PCM will see Park/Neutral or In-Gear just as it should. It will operate the Idle Speed tables correctly and add or remove IAC counts to compensate for the load change. I always add enough steps to keep the engine from having a large RPM drop on the Park to Reverse shift. Reverse has the highest engine load. I set the Park/Neutral table about 75-100 rpm higher than in-gear. Makes the transition feel relatively seamless without the RPM dipping and activating the stall saver routine. I have yet to find a factory application that was TCC only so you would not find this on a wiring diagram. I figured out the TCC was on E10. The TCC only application did not seem to have coding for a High Gear switch or I never found it if it existed.
https://www.thirdgen.org/forums/tbi/...rting-tbi.html
4.3 V6 with a 5speed wiring diagram should show where to input the clutch switch too. The PCM uses the clutch signal for the spark smoothing. The PCM will alter timing and IAC counts to help you launch off-idle and shift the trans more smoothly. The clutch switch will also keep the RPM from spiking when you press in the clutch pedal coming to a stop. The factory upshift light control is on pin E2 and is enabled when you select manual trans option. You can adjust the light to come on at various TPS vs RPM and set the NV table correctly for the SM465. I had it programmed correctly and functioning on a 3spd column shift truck. I used a relay to control an amber bulb.
Last edited by Fast355; 01-28-2020 at 09:24 AM.
I am putting a GM TBI unit in my 1974 K10 and am using the 1227747 ECM. I'm trying to make the check engine light come on and per the ECM schematic I need 12v switched to the bulb and a brown/white wire going to pin A5 which grounds out inside the EMC. I've checked everything I can think of, good bulb that works, 12v to the bulb, and the light won't come on. Does this mean the ECM is bad or could it be something else
In response to your same question on TGO...double, triple, quadruple check your wiring. Idk what schematics you have that would have the A5 spliced to go to pin D on the ALDL... There's some schematics at the following link... http://www.gearhead-efi.com/Fuel-Inj...Information-42
In the 1227747 schematics you sent me, the schematic on the top row far right is the schematic I have which shows the spliced brown/white wire going to pin D in the ALDL.
Found the attached .pdf on the web, looks correct to me.
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