Hey there, really hoping someone can help.

I've been chasing idle and running problems with my Evo 4 for a long time. When I first got it in August 2019, bone stock except for cat delete, it idled and ran not too bad at all. Replaced the rusted out wastegate actuator and all was well for a couple months. Then I started having random surges and jerking after starting the car up while warm, accompanied with an engine light while it happened. Eventually the car got worse and was surging and jerking all the time. I parked it and have been trying to solve this for months.

To rule out some things: Previous owner replaced fuel filter right before I bought it. Alternator is brand new, as is the battery. I replaced stock air filter, spark plugs with BR7ES gapped to 0.65mm, idle air control valve, cleaned E4 MAF & throttle body, checked for vacuum leaks (car sits at 14-15 in/Hg, checked with manual gauge), and checked compression (135-141). Also have tried running it on a COP ignition system.I know compression is low but I just need this engine to last another year. Should run okay because the numbers are close, if I'm not mistaken. I scanned the engine code (shorted pins 1 & 4 on OBD) and got code 12, airflow sensor fault. My OEM E4 MAF sensor was cracked open and I figured that was it, but no. I've tried 2 used E6 MAF sensors, and an Ebay sensor for a Montero that fits the same. With one of the E6 MAFs it ran fine for a day, pulled fine and felt good. Then the next day I connected the 2 wires for my rear O2 Sensor (to get rid of hot cat light due to cat delete) and after that it started running like ****. On the Montero MAF it throws code 12 and runs super lean, if you rev you can hear it sucking in tons of air but no acceleration. On the E6 MAF it fouls the plugs with carbon deposits immediately and runs super rich (or so I thought). The only real mods that would affect airflow on the car is a cat back HKS exhaust with cat delete, 3" K&N cone filter, and a turbosmart recirculating bypass valve. I have a catch can but it is not vented. There is no air leaks between MAF and manifold. Not applicable really but I also replaced the lifters, valve cover gasket, and oil pan.

Since then I got it to work on the E4 MAF by tapping it with a screwdriver. The light went away and the idle stabilized. I took the car for an hour drive thinking it was all good, but today I got my AEM wideband and installed it. The AFRs on the E4 MAF started out at 14-15 as it warmed up, but once engine was warm and I was driving the readings shot up to 18+. It wouldn't even show on my gauge. It horrified me that I drove it for so long without a wideband and I took it home and parked it. I installed my Evo 6 ECU and injectors, hooked up my OP 2.0 cable and datalogged my idle for a minute with EvoScan.

TPS, battery voltage, air temperature, airflow rate gm/s, and barometric pressure sensor readings all seem to be okay. However;

Idle is all over the place, wasn't giving any gas

Timing advance is all over the place. Jumps between 1 and 24, this surely cant be good. I have checked the timing parks on the belt and cam gears and it all lines up.

Injector pulse & duty goes between 1 and 3.5 at idle. I assume this is because it is getting incorrect fuel pulses from skewed air readings.

Airflow reading (I'm guessing what the MAF sees) went from 37 to as high as 100 at a point. I think there is something wrong in the wire between MAF and ecu. All the power and grounds are good in the MAF connector but I never tested the sensor wire. It had an AFC Neo spliced into it with butt connectors, I removed it and re soldered it, but is it possible this wire has corroded causing the huge range of readings its giving off?

Air volume is all over the place as well but I've heard that's normal.

O2 Sensor voltage never went above 0.06, I've read it needs to be 0.1 to 0.9 volts. I never replaced the OEM E4 O2 sensor with the 4 wire heated E5< O2 sensor. Could this be what caused the low readings?

My knock count went up to 3. I know this isnt good especially if I'm just idling. On my first log it went up to 7.

AFR map is coming back as 14.7 but I believe this is just a target range? Is it functioning correctly?

I don't have my wideband hooked up to my laptop so I can't include the true AFR readings in the log, but as soon as I started the car with the Evo 6 ecu, injectors, and MAF, it ran at 14.7 AFR for like 10 seconds and then shot up to beyond 18 and never went down for the rest of the time it ran. This was my 4th log and is all just idle, no throttle at all. I am running a full tank of fresh 94.

This is all the information I can give. I've asked tons of mechanics and posted on reddit about these issues but I never have found someone who can fix it. I figured now that I had the log it would be easy to check it out and give me some feedback on what needs to happen. Can this simply be fixed now by editing my rom/flashing a new one? Could my MAF wire be causing all these problems? I have heard of CeddyMods but do not know what it is, would this be a solution? I hope someone can give me some info, and if I need to be pointed to a tuner or something that costs some money its all good, I just want this car to run well and I am so close, this is my only lingering problem. Thanks in advance everyone.

Here's a picture of my car https://drive.google.com/file/d/1hyu...ew?usp=sharing

 

The E4 and E6 mafs are slightly different so it would be best to use matching set. Bad 4 maf on 6 ecu could be even worse?
Did you reset the biss at all? I didn't see that mentioned.
The rear "O2" sensor is only a temperature sensor for cat overheat. I'm not sure it sends any info back to ecu that would mess with anything. You need to put a resistor in there if you want to connect the wires.
Get the right o2, ecu, maf combo confirmed and working. Check and fix the wiring. Adjust the biss and see how it goes.

I think there's an ecu setting to turn sensor heating off if you don't use a 4wire.

 

I can try too help you. If your problem doesn;t solved yet. I done around 10 evo 4 cars with different (evo 5 6 7 8) ecus.