Sort of.I understand that, but it also tells the ecu where the timing is.
Bench tested AFM per the FSM, all tests passed except for the air temp test but it was JUST out of the ohm range. This wouldn't cause my issue because it still is providing a value to the FSM which is within range, so if anything it's just telling the ECU the temp is a bit off from what it actually is
OK glad you have his issue figured out.Sort of.
There is no feedback to the distributor from the ECU. The distributor is simply supplying 2 sets of tach pulses to the ECU which it processes according to its programming. Timing will depend on throttle position, knock sensors (if so equipped), AFM input, etc., but it is all done by the ECU.
Again, the distributor does not change or alter timing in any way.
On the 3FE, the crank position sensor was one of the tach pulses in the distributor. On the 1FZ-FE (I think both US spec versions) there is a separate crank position sensor that the ECU uses to reference timing.
Check that, the ECU uses the camshaft position sensor (one of the tack pulses) in the distributor to reference timing on the 1FZ, just like the 3FE. The crank sensor monitors RPM according to the FSM.
Have you pulled the plugs to inspect?
Maybe a long shot, but is it worth confirming throttle position sensor input vs. output? Or swapping in a known good one?Midday update:
So to date, I've done the following:
- Swapped over distributor - NO CHANGE
- Swapped over Ignitor - NO CHANGE
With everything above checking out I think it's safe to say the issue isn't in the ignition side. Here's some more info that we noted while testing it today:
- Cleaned all grounds and + terminals
- Swapped ECU with my Spare
- Swapped Wires, Distributor Cap, Rotor with my Spares
- Swapped Coil with my spare
- Checked the AFM per the FSM and it passed every test (see post for info)
- Set timing back to 5 degrees
- Tested Fuel Pump Voltage at the pump, noted it was low on high flow, hot-wired to get 13+ volts to it at high flow. NO CHANGE
- Check Engine Codes have not returned since the original post
The stumble happens under 3/4 to full throttle (load) more noticeably / harsher at 2500 - 3000 then less harsh but still noticeable at 3000-4000, and not discernible above 4000 rpm.
My buddy who is a super secrete squirrel black ops UAV helicopter engineer/fabricator, who is also the dude that let me borrow his 80, said it felt fuel related to him. I've got a spare fuel pump and fuel pressure regulator in my bins that I'm going to bench test and throw in tonight, other than that I'm thinking injectors or wiring?
I'd like to get a data logging oscilloscope for my iPad so I can log when each of the injectors are getting pulsed during driving. But since it doesn't happen under light load through the same RPM I doubt it's a wiring issue. I'm thinking it's a sticking / failing injector since low fuel pressure would probably result in more noticeable issues at the top end rather than down low.
Oh, and I have a text out to my bud who I sold my old 93 to just to see if I can borrow his AFM and rule that out.
How does my logic check with you guys? Thoughts? Am I missing anything?
Whats my next diagnostic step?
- Verify Fuel Pressure at the rail? I'd need a remote gauge so I can see it while driving
- Buy one injector and just move it down each cylinder to see if I find the dead one?
- Replace the fuel filter (50k on this one)
Check your grounds.
There are several in different places.
Like from valve cover to firewall, intake to firewall, battery minus to fender, coil (igniter) to engine block, etc.
If in doubt, run a temporary one anyway to see if it helps. Some times a bad ground can cause all sorts of strange things to happen.
If there's a cluster of ring lugs, remove the bolt/screw, clean lugs with scotchbrite, add dielectric grease and retighten.