Random Misfire

[Jarsky]

11 hours ago, idosubaru said:

OBDII is meaningless here - pre OBDII stuff still gives codes. When you read the check engine lights what does it show?

If it stumbles take notice if its:

1. recently wet/humid

2. happening when you let off the gas entirely (throttle closed)

3. is it ever hard to start or restart?

Do you have access to spare parts?

Hate to suggest guessing but MAF sensors are easy to swap on EJs and I’ve seen them cause starting and drivability issues without throwing a code  

The grounds are probably to the frame rail, I do t recall Subaru grounds on any radiator I’ve worked on. But maybe that’s indicative of my memory?!? Lol

It’s unlikely the grounds anyway. Almost every Subaru I see and drive has corroded and detached grounds and runs fine. Yes they can be problematic but that pic looks like a clean car, engine came out and you had a good look at it and it starts.

i dont recall if it was recently wet, it would happen at WOT on the highway and not entirely hard to start or restart. I do have some spare parts. 

[idosubaru]

What check engines codes are showing when the  check engine light codes are accessed ?

It only happens at WOT?

[heartless]

just going to add to the confusion, i am sure.. but ...

many years ago - 89 GL wagon (EA82) started running like crap going down the highway - misfiring, etc, limped into a fuel station and found a cheap plug wire was arcing - also ended up with a bad O2 sensor on that car due to the misfiring. would stumble, misfire and run like crap even after putting good wires on - took it a long time to throw the code for the O2..

95 Legacy had random misfiring but usually on initial startup - would run like crap until warmed up.. after paying closer attention for a few days, it was always on damp days.. fog, rain, whatever... pop the hood and could actually see the arcing from the coil in full daylight when it was acting up. have a short video somewhere of it.

[Jarsky]

4 hours ago, idosubaru said:

What check engines codes are showing when the  check engine light codes are accessed ?

It only happens at WOT?

i havent checked, because of the manual swap theres always a check engine light, and it can happen at WOT or at idle, i was just giving that as an example.

[Jarsky]

1 hour ago, heartless said:

just going to add to the confusion, i am sure.. but ...

many years ago - 89 GL wagon (EA82) started running like crap going down the highway - misfiring, etc, limped into a fuel station and found a cheap plug wire was arcing - also ended up with a bad O2 sensor on that car due to the misfiring. would stumble, misfire and run like crap even after putting good wires on - took it a long time to throw the code for the O2..

95 Legacy had random misfiring but usually on initial startup - would run like crap until warmed up.. after paying closer attention for a few days, it was always on damp days.. fog, rain, whatever... pop the hood and could actually see the arcing from the coil in full daylight when it was acting up. have a short video somewhere of it.

well the O2 was replaced a couple months ago, and the car has NGK plugs that are relatively new. I did realize that the ignition coil(i think that's the name) was somewhat lose. I had to give it a bit of force to move but im sure if it hit a bump it might move enough to cause some sort of problem. That has since been tightened but because of how random the issue is I'm not sure that was the problem. 

[1 Lucky Texan]

I think they still list the flash-codes from '83 up at;  https://www.troublecodes.net/subaru/

[idosubaru]

3 hours ago, Jarsky said:

i havent checked, because of the manual swap theres always a check engine light, and it can happen at WOT or at idle, i was just giving that as an example.

Manual swap is irrelevant. I don’t know why that keeps coming up, it doesn’t matter at all.

Check the codes.

Ignore the codes due to the trans swap.  

what other codes exist?

People ignore emissions, engine swap and trans swap and turbo codes all the time. swaps give a 100% predictable set of codes, most/all of which don’t impact drivability, they just ignore them. All the rest of the potential codes are relevant.

Typically problematic codes are MAF knock cam crank injector misfire O2....none of which are impacted by trans swaps. If those are set then they’re telling you there’s an engine issue not related to the trans swap. 
 

[Jarsky]

2 hours ago, idosubaru said:

Manual swap is irrelevant. I don’t know why that keeps coming up, it doesn’t matter at all.

Check the codes.

Ignore the codes due to the trans swap.  

what other codes exist?

People ignore emissions, engine swap and trans swap and turbo codes all the time. swaps give a 100% predictable set of codes, most/all of which don’t impact drivability, they just ignore them. All the rest of the potential codes are relevant.

Typically problematic codes are MAF knock cam crank injector misfire O2....none of which are impacted by trans swaps. If those are set then they’re telling you there’s an engine issue not related to the trans swap. 
 

ill take a look when its not raining and see what i can find 

[idosubaru]

3 hours ago, Jarsky said:

ill take a look when its not raining and see what i can find 

Hahahhaa. The rain and ice is annoying, from freezing cool wet straight to 85 and humid this year...eye roll

If you get any codes (or any non swap codes), post the numbers and not descriptions or what online or auto parts stores tell you

if you’re unsure - clear them all and see which ones come back immediately (like the first mile and 10 miles).  It could trip some right away and then others later. 

if you can access a memory mode - read those too. Same thing - clear those as well so any new codes have a clean slate. 
 

 

Edited May 9, 2021 by idosubaru

[jonathan909]

Laugh it up, folks.  We woke up to 2" of wet snow this morning.

[heartless]

10 hours ago, Jarsky said:

well the O2 was replaced a couple months ago, and the car has NGK plugs that are relatively new. I did realize that the ignition coil(i think that's the name) was somewhat lose. I had to give it a bit of force to move but im sure if it hit a bump it might move enough to cause some sort of problem. That has since been tightened but because of how random the issue is I'm not sure that was the problem. 

NGK plugs are good - but what about wires? Cheap parts store wires are known to be problematic on these cars (as noted with the GL wagon - those wires were only a month old when the problem happened). Use OEM or NGK wires only.

[Jarsky]

On 5/9/2021 at 8:36 PM, heartless said:

NGK plugs are good - but what about wires? Cheap parts store wires are known to be problematic on these cars (as noted with the GL wagon - those wires were only a month old when the problem happened). Use OEM or NGK wires only.

Sorry for the drop off Ive been super busy. So I have ngk plugs and wires, the random misfire has disappeared, I'm blaming that on the loose ignition box. However I have a new problem (don't know if I should start a new post it not). Sometimes when driving the car, and this is very rarely, about once a month, after I park the car for a bit and go to get it started again there's a loud buzzing noise and the rpms jump too 3000, that's just in accessories. When I go to crank the rpms go to 4k. The car won't start when this happens and I quite literally have 0 clue what it could be.let me know if this is new post worthy.

 

[1 Lucky Texan]

i know it's random, but maybe at every opportunity, have someone start the car while you listen with the hood up for the location of the noise? i THINK IAC valves can buzz. Early 90s have had buzzing ABS pumps, but I don't think that will prevent starting.

[Jarsky]

On 6/20/2021 at 4:43 PM, 1 Lucky Texan said:

i know it's random, but maybe at every opportunity, have someone start the car while you listen with the hood up for the location of the noise? i THINK IAC valves can buzz. Early 90s have had buzzing ABS pumps, but I don't think that will prevent starting.

i believe i figured it out, the car has a koyo rad for a 3d gen outback in it and because the plugs are different the fans are wired to a switch in car, leaving the stock fan plugs wide open. Discovered the other day that the rad was leaking out of a ripped block of plug, since replacing that the issue hasn't happened. Im guessing maybe the coolant was dropping into the plug and that cause it to arc. Hopefully it holds up!  thanks to anyone that post suggestion!