Hi guys, I have a ae86 hatch and recently did a 20v blacktop swap. All good with the swap, I have a distributor relocation kit (SAM). The engine is running perfect at idle, runs incredible on WOT, but if I slowly rev it, when it get's past 3500 rpm it starts to hesitate and sometimes misfires. Even if I try to keep it constantly at 4000rpm for example it boggs... I checked all the sensors, sta wire, timing, everything is at it's place... new O2 sensor, coil, spark plugs, rotor... No CEL codes what so ever. I can't seem to sort this one out. I've been killing the internet these last few days but nothing works. Maybe someone has an ideea and is willing to help me. Cheers guys.

Not too sure... but is 4k about when VVT activates?

I've unplugged,plugged and is the same, its running eye burning rich, checked also the ecu and its in good shape.

Midrange hesitation is very common on the AE111 blacktop, and while there
are plenty of opinions, there are no proven causes or cures. Here are a few
things that are said by various owners to have helped (at least for a while)...

- Clean the throttle bodies (no idea why this would work).
- Make sure you have a SPD input to the ECU.
- Use the highest octane fuel you can get (BT does not like crap fuel).
- Install a catchcan (keeps oil fumes out of the intake).
- Fit a new OEM Toyota O2 sensor (apparently works better than generics).
- Clean the O2 sensor to remove/burn out soot clogging the sensor.
- Check that the knock sensor is not faulty.
- Check that the VVT solenoid is working correctly (valve moves freely).
- Check the engine thermostat is working correctly (not stuck open)..
- Don't use oil thinner than 10W40 (reduces oil consumption).
- Fit a new fuel filter (cures everything except baldness).
- Check the coil for carbon tracking (spark short circuiting).

The only two halfway decent theories I have come across are (1) that the knock
sensor is pulling timing in the midrange, and (2) that the O2 sensor is liable to
drift to read lean, causing the engine to run rich. And since the engine already
runs rich even on a good day, this could be enough to cause a rich misfire. Neither
theory is hard proven by test, so if you have a WBO2 gauge installed, you could
at least check out theory #2

Cheers... jondee86

Thank's Jondee86 for for the reply
I did the following:
-Clean the throttle bodies (no idea why this would work). -Check
- Make sure you have a SPD input to the ECU.-Check. (The car misfires even if standing still. I press the gas 1/4 it starts revving, and when it reaches 3500 it instantly starts ti hesitate, sometimes misfire. On WOT it goes pretty well, sometimes it does the same there aswell.. but just sometimes.
- Use the highest octane fuel you can get (BT does not like crap fuel). -Check
- Fit a new OEM Toyota O2 sensor (apparently works better than generics). I have new o2 sensor installed.
- Check that the knock sensor is not faulty. -Checked sensor and wire to ecu also.
- Check that the VVT solenoid is working correctly (valve moves freely). -Check. Working.
- Fit a new fuel filter (cures everything except baldness).
- Check the coil for carbon tracking (spark short circuiting). -Check. Just installed new rotor, cap is mint, tried new coil..
The only thing I can say is wrong is the valve lash at 1 maybe 2 valves.. I can hear them ticking but it would be impossible to be the reason for my problem.

Cheers. Alex.

I would also sync the throttles, this helped with my midrange hesitation.