EJ22 Random misfire when warmed

[alexbuoy]

Hello all thought i’d try my luck here coming from the 80’ s subaru forum.

I've recently transplanted a 1998 EJ22 265k miles into my Subaru Brat. The EJ along with the wiring harness was out of my Loyale, which ran great before it was pulled.

When I first wrapped up the swap it ran amazing. Did some pulls with it at operating temps with no issues. Now it’s missing quite bad when it gets to operating temperature. And it’s  also been getting worse. No CEL’s which is leaning me towards it being a fuel issue.

Modifications to the engine/fuel system.

1. Short Ram intake. All of the vacuum lines are connected after the MAF

2. Fuel Cell

3. Straight pipe with no cats. o2 bungs are welded in (gave no issues when the EJ was in my pryor car)

 Also I cleaned/replaced the following

1. IACV

 2. MAF

 3. used Engine Coolant Temp Sensor

4. used Ignitor

5. New fuel filter

6. used coil pack 

7. cleaned PCV

8. new plugs less than 5k ago

What I’ve checked 

1. No vacuum leaks whatsoever

2. Timing is good 

Im going to try replacing the fuel injectors and FPR.

Any ideas? I'm super stumped it started acting up a couple of days ago.

Edited July 12, 2018 by alexbuoy

[Subaru Scott]

I think I would start with a new coolant temp sensor.

[alexbuoy]

2 minutes ago, Subaru Scott said:

I think I would start with a new coolant temp sensor.

That was my thought too. I replaced it with a used one off my parts engine. My scanner shows that the ECU temp is about 10-15 degrees off from my mechanical coolant temperature sensor. although I do not know how accurate either are

[montana tom]

Check compression,  got a tight valve?

[1 Lucky Texan]

does it run better immediately after an ECU reset? If not, I'd look for a physical problem; vacuum or intake mani leak or dropped valve guide/tight valve as mentioned, etc,

 

if it does run better after a reset, probably a bad sensor - a:f or knock sensor.....? maybe as simple as cleaning the MAF  ???

[alexbuoy]

Currently it runs pretty bad cold or warm. Pulled the plugs today and all 4 were fuel fouled and had a strong smell of fuel. 

I’ve also swapped my fuel rail and fuel pressure regulator with a known good one.

I just checked my AFR sensor, wires are frayed a bit. I’m going to try replacing that and also upgrade my fuel return line since it’s only 1/8”.

Would a bad AFR really make the car run that poorly ?

[1 Lucky Texan]

look for wetness/fuel in the vacuum line from the FPR. sometimes the diaphragm leaks.

 

does your scanner get fuel trims?

 

 

Edited July 16, 2018 by 1 Lucky Texan

[alexbuoy]

1 hour ago, 1 Lucky Texan said:

look for wetness/fuel in the vacuum line from the FPR. sometimes the diaphragm leaks.

 

does your scanner get fuel trims?

 

 

Unfortunately my scanner does not do that. The vacuum line that goes from the FPR to MAP does not show any signs of raw fuel inside.

Im thinking because my fuel return line is so small (ej swapped brat) the fuel pump is over pressurizing the system. 

Im going to upgrade the fuel return and o2 and i’ll check back.

 

Edited July 16, 2018 by alexbuoy

[alexbuoy]

Replaced AFR sensor and plug wires. upgraded the fuel return line to the tank to 5/16 also. Also replaced crank sensor. I’m super stumped! I don’t think it can be low compression/bad valve since all 4 plugs were gas fouled???

[alexbuoy]

ECU reset did nothing also

[1 Lucky Texan]

to me, if the ECU reset didn't help, that points more towards a physical problem.

it still may be useful to get live data. A smartphone app and a ELM327 BT adapter

or, do as Montana Tom suggested and get comp. readings. Vacuum gauge testing is occasionally helpful.

[heartless]

what about the plug wires? have they been replaced, and if so, what kind?

Auto parts house wires are junk and are known to cause issues. Wires should be either OEM or the appropriate NGK set for the motor.