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859 Posts
hi everyone.
had a couple newb questions about some TBI wiring on a 4.3. I got a 1993 TBI 4.3 at the junk yard, but it didnt come with a harness (well it had a couple plugs still but was hacked up), so I found an 88 astro that I pulled the harness and ECM out of. The two are TBI and 4.3 so it should be plug and play right? Not quite... The TPS, oil pressure, and a few other plugs were different. The oil press sensor plug had 2 pins on the astro harness, but the 93 motor OPS had 3 pins. The astro harness also deosnt seem to have any plug for the EGR. The 93 EGR motor plug has a 5 pin connector. Im not gonna run EGR, so can I just leave everything as-is without a check-engine light? The TPS plug was different, so I spliced the 93 style TPS plug onto the astro harness. There is also this two pin connector that comes out of the astro harness right around the TPS and MAP sensor connectors...I have no idea what its for. The 93 engine didnt include the spark control module so I need to find one (the astro harness has a flat wide 4 pin connector for the spark module).
The astro harness was also wierd in that it had two bulkhead connectors. One passed thru the firewall that JUST had ECM wiring in it. The other bulkhead connector on the driver side had all the ign, data, guage cluster info, etc crap. Anyone have any idea where I can find a pin-out for that drive side bulkhead connector so I can find IGN, oil press info, etc wires?
also im running the 4.3 to a TH400. The astro ECM and harness was obviously setup for a 700r4. But reading the ECM schematics it appears in 4.3/TH400 apps, one of the output from the ECM triggers the electronic kickdown on the TH400. Any place I can get a custom PROM chip to have the ECM setup for a TH400, no EGR, and stuff??? I tried affordable fuel injection but they wont sell the PROM chip alone, only WITH their harness...:mad3: Its the '7747 ECM which I understand is the main ECM supported with aftermarket.
So basically....are there any other issues that would make my 88 astro harness not work with my newer 93 TBI engine? Why does the oil press sensor have two pins on the astro and three on the 93? Whats the deal with EGR and TPS? I have a couple other mystery wires and plugs Ill post pics of...
VSS is another issue. Its going to be a 4.3 to TH400 to quadra-trac xfer case....so I rebuilt the chevy TH400 with the wierd 10 spline q-trac output. But now I dont have the tone wheel for the electric VSS that was on the original chevy TH400 output. Is this going to cause a problem with the engine, like going into idle mode, spark offset, DFCO? I dont want a check engine light from it either...can that be turned off with a custom chip?
Ill try to think of any other questions...go easy on this newb fawker tho.:flipoff2:
thanks
ben
had a couple newb questions about some TBI wiring on a 4.3. I got a 1993 TBI 4.3 at the junk yard, but it didnt come with a harness (well it had a couple plugs still but was hacked up), so I found an 88 astro that I pulled the harness and ECM out of. The two are TBI and 4.3 so it should be plug and play right? Not quite... The TPS, oil pressure, and a few other plugs were different. The oil press sensor plug had 2 pins on the astro harness, but the 93 motor OPS had 3 pins. The astro harness also deosnt seem to have any plug for the EGR. The 93 EGR motor plug has a 5 pin connector. Im not gonna run EGR, so can I just leave everything as-is without a check-engine light? The TPS plug was different, so I spliced the 93 style TPS plug onto the astro harness. There is also this two pin connector that comes out of the astro harness right around the TPS and MAP sensor connectors...I have no idea what its for. The 93 engine didnt include the spark control module so I need to find one (the astro harness has a flat wide 4 pin connector for the spark module).
The astro harness was also wierd in that it had two bulkhead connectors. One passed thru the firewall that JUST had ECM wiring in it. The other bulkhead connector on the driver side had all the ign, data, guage cluster info, etc crap. Anyone have any idea where I can find a pin-out for that drive side bulkhead connector so I can find IGN, oil press info, etc wires?
also im running the 4.3 to a TH400. The astro ECM and harness was obviously setup for a 700r4. But reading the ECM schematics it appears in 4.3/TH400 apps, one of the output from the ECM triggers the electronic kickdown on the TH400. Any place I can get a custom PROM chip to have the ECM setup for a TH400, no EGR, and stuff??? I tried affordable fuel injection but they wont sell the PROM chip alone, only WITH their harness...:mad3: Its the '7747 ECM which I understand is the main ECM supported with aftermarket.
So basically....are there any other issues that would make my 88 astro harness not work with my newer 93 TBI engine? Why does the oil press sensor have two pins on the astro and three on the 93? Whats the deal with EGR and TPS? I have a couple other mystery wires and plugs Ill post pics of...
VSS is another issue. Its going to be a 4.3 to TH400 to quadra-trac xfer case....so I rebuilt the chevy TH400 with the wierd 10 spline q-trac output. But now I dont have the tone wheel for the electric VSS that was on the original chevy TH400 output. Is this going to cause a problem with the engine, like going into idle mode, spark offset, DFCO? I dont want a check engine light from it either...can that be turned off with a custom chip?
Ill try to think of any other questions...go easy on this newb fawker tho.:flipoff2:
thanks
ben