olong_us

OK im putting a fresh 89 roller 350 TPI into my 86 Iroc that origionaly had 305 TPI. At the advice of another member i need 86 and 89 ECM pin out diagrams to see what i will have to change in the wiring harnes if anything. Thanks Alex

S10Wildside

Here's the only changes I can think of:

1. The 89 TPI engines use a different oil pressure switch. It's located above the oil filter and contains the sending unit.
2. The cold start injector is eliminated in 89.
3. The front accessories are configured differently beginning in 88.
4. The 87 and newer alternator uses a different plug.
5. The alternator and A/C compressor are in different locations.

If you are still working with the 86 wiring, just replace the 89 engine's oil pressure switch with the switch and sending unit on the 86. As long as you use the memcal from the 89 ECM, you will have no cold start issues. The cold start circuit has nothing at all to do with the ECM harness. You can somewhat easily pull it out of the engine harness.

The only difference between the 86 and 89 ECM pinouts is the VATS circuit for the 89 ECM. If you use an 89 memcal and have VATS removed you will be good to go.