I didn't want to have to update this thread in a negative manner, since I've been doing a lot of work, replacing everything including the engine over the past 6 months. However, even after my engine replacement, the slight miss/shake at warm idle still exists.
Since last time, relevant parts replaced:
- New OEM igniter
- Adjusted original TPS again (more on this later)
- Rebuilt/flow tested fuel injectors
- OEM fuel rail
- OEM fuel filter
- Plenum/intake manifold/TB gaskets
- Engine
- OEM Cold Start Timer Switch
- OEM Coolant Temp Switch
- Intake and Plenum professionally restored (hot tanked, threads chased, new freeze plugs, powder coated)
Parts Checked (in addition to above original post):
- IACV: coolant flow is perfect/no blockages, Ohms at 50, slightly open vane at room temp, opens more after 30 min in freezer -> cannot be IACV at this point
- AFM: rechecked this again at the AFM (haven't done ECU yet), all in spec
- TPS voltage/resistance at ECU -> VTA voltage was spotty, not in spec, so I jiggled the connector -> got it back in spec but still random miss -> this is my current hypothesis on what to fix to get this problem nailed down
What's Left (in order of what I think will fix it):
- TPS Connector -> since I had issues at the ECM side for VTA voltage, this is definitely an issue. Will inspect the wiring beyond the connector to the harness and splice in if necessary.
- New OEM TPS on order -> I had ordered the wrong one (-20050 instead of -20060), which bites us 1985 owners as there is a split in production year from 7/1985 to 8/1985 where the TPS model # changes. Mine is production date 2/1985, and all the parts sites show both fit (even Toyota) because you can't enter a production date. Anyone needs a brand new OEM -20050 TPS for a steep discount
?
- Fuel Injector wiring -> going to solder on new connectors, and solder/new wire for the crimped 1 to 2 and 2 to 4 connections
- Fuel pressure regulator -> tests with pinching vacuum checked out, but I'm going to replace it anyway
- Fuel Pump -> no indication it's "bad" but I know it's a NAPA part and I simply don't trust anything but Toyota/Denso for mechanical/electric parts. Lower on the list
Currently, it throws a code 7, which means TPS short or ECU problem. Since the sensor side of the TPS can be adjusted and checks out, and I uncovered that VTA voltage issue, I can only assume the TPS itself is good, but the wiring is bad. Either that or the ECU is toast. So I'm banking on replacing the connector/wiring in the TPS circuit to solve the issue. But I'll still replace the TPS since mine is original 1985. I'm having a hard time trusting the multimeter right now given everything I've checked that hasn't solved the problem.
I still wonder about the AFM. Everyone on forums blames the AFM for everything related to idle issues and starts adjusting things that don't need adjusting, even if it's in spec. Any thoughts that I should find a good used one for the hell of it if it's cheap? I refuse to open it up, as it seems that just causes more problems. Plus, my engine is completely stock replacement, no aggressive cam, porting, boring, etc. So there should be no need to adjust the AFM at all.
Again, any suggestions would help. You can imagine my frustration after replacing the engine and basically everything else under the hood with quality OEM parts, to still have this stupid shaky warm idle and random put, puts.
