Hello everybody!

Just got done working on the AE86. 4AGE 16v.

I replaced the fuel pump, and the fuel sender unit.

The car is now running better than ever, and idling well at around 900rpm. I'm still running into the same issue again, and need some help:
-Engine revs perfectly fine in neutral and when not under load
-Once under load (in gear), the engine will not rev any higher than 3000-4000rpm
-When the engine hits this limit, it stops firing and check engine light briefly comes on
-I am continually unable to rev above this limit when in any gear

Things I have done:
Spark plugs
Check for vacuum leaks
Fuel pump
TPS adjustment

Things I suspect:
AFM? I do not know much about it
Faulty wiring somewhere down the line
Something on the car telling the ECU to not let the engine fire above the aforementioned revs

When the check engine light comes back on, while driving, pull over, pop the hood, and check for codes. Don't turn off the engine while you're checking. Hopefully it'll lead you in the right direction.

Or you can grab your multimeter and ohm everything per the FSM/BGB.

G'luck friend.

I would start off by checking that code. That will get you into the ball park.

Otherwise, I would say its probably your air flow meter. However, check the code first.

Check AFM and igniter

Alright makes sense but as soon as I take my foot off the throttle, the CEL turns off, it's only on when I'm hitting the rev limit. Will I still be able to test it?

should have the code stored in memory

So I found out it's unmonitored air entering the engine, messing up the A/F mixture and causing it to stop revving. I'm buying a new intake from Injen since I need to be able to hook up the IAC to it.

If its unmonitored air, that either means your AFM is bad or the circuit for the AFM is bad. Either that or you have a huge vacuum leak.

Cracked exhaust header above O2 sensor??

Haven't taken a look at the exhaust header yet, but the intake hose was very old and cracking. So waiting on a new intake to come in the mail and it should solve the problems. Also debating on 100% deleting the IACV. Decisions decisions.