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1998 Impreza 2.5rs
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35 Posts
Discussion Starter #1
I just got my 98 rs back up and running after the previous owner decided to only get one head machined and left the other alone which caused weird compression and threw everything out of whack, but now that's solved I'm encountering a new problem with the car just dying randomly while driving/stopped and also under hard braking, when I brake before it happens the oil light comes on very slowly for a brief second and then all the lights come on because it died. If anyone has had this issue or atleast knows how to fix it I would love advice.
 

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'01 RS+t STM
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1,190 Posts
checking post history, looks like an auto to manual swap. what do you mean the light comes on slowly? like dim to bright? the bad boy triggers at only like 2-3psi. is your oil filled to spec? Keeping enough gas in it? I know these like to fuel starve in high g situations.
 

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1998 RS #2
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5 Posts
Does it die while cruising or only when stopped/coming to a stop (only when idling)? I would check for intake leaks and take a look at the idle air control valve.
 

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1998 Impreza 2.5rs
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35 Posts
Discussion Starter #5
It's manual swapped, the light comes on very slightly dim and then everything lights up when it dies, it doesn't happen everytime and the oil is full. My fuel tank is full too that actually caused another issue of my gauge being pegged at full and throwing a low fuel sensor level code. The car dies whiling driving or at a stop, it hasnt done it when just parked and letting it idle. I was suggested to try a different maf sensor, I did and it still dies. I've also notice sometimes the battery comes on first sometimes then dies.
 

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Black 2001 RS
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783 Posts
Sounds like a loose wire somewhere. Perhaps the force of slowing the vehicle is just enough to break a circuit.
or...

It could also be the IACV being slow to react. Does this occur if you've been coasting for a few seconds and then try to stop. Although that might not do it since you're off the throttle and the IAVC has time to settle.

If you're stopped in neutral and you rev the engine and let off the throttle quickly, does the behavior show itself?
 

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1995 EZ30 Coupe
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464 Posts
My vote is iacv, although sometimes I swear it's related to break signal input. Mine is manual swapped and will stall very rarely, at the same two stops. One is down hill to a stop sign, the other is an off ramp, and it always happens after long periods of engine breaking, followed by shifting to neutral and applying the break.

Couldn't hurt to double check your wiring.
 

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1998 Impreza 2.5rs
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35 Posts
Discussion Starter #8
Someone else suggested the IACV too they said to just clean it and if that doesn't work try a different one. I'll try those and see if it helps
 

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1998 Impreza 2.5rs
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35 Posts
Discussion Starter #9
If I'm stopped and rev it the problem doesn't occur, it's only while driving, coming to a stop or sitting at a stop light. There is no consistency either, it happens when it feels like it. Sometimes it happens quick or it takes a while. I don't know if this helps with people trying to help me but it does run rich and has a consistent miss on 1&3 cylinders, but there's no rough idle, idk if those issues together mean one thing specifically, but I'll keep trying things
 

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1995 EZ30 Coupe
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464 Posts
After some testing, it seems to stumble and bog after engine braking for more than a couple seconds. The brake doesn't seem to be necessary, but can cause the symptoms even without engine braking.

I'm gonna try rewiring my car so instead of thinking it's in 'D' when in gear, it'll think it's in '1'. In my head, that'll hopefully prevent my recurring IACV codes (0507/1507) and stop the stalling.

I believe a manual cam and crank trigger are required to swap to a manual ecu. Probably some additional wiring. Does anyone know if there's anything else? IACV?
 

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1998 Impreza 2.5rs
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35 Posts
Discussion Starter #12
So I finally got a code for 1507 idle control failure which hopefully means you guys are right, so tomorrow I'll be picking up a different one. I really hope it solves the issue because I figured out the consistent 1&3 miss was because cylinder 1 injector was popped out of the rail a little I probabaly didn't completely seat it when I installed new o-rings, it's all good now though.
 

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www.jackstalk.com
04 WRX, 911 Cab, Escalade ESV
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5,372 Posts
Ive known several people that did auto-manual swaps on their 93-01 subarus and every single one of them experienced idle issues and the car randomly dying. I dont remember if anyone remedied the situation but i know bansheeboy11 has some experience with this happening on two different cars. Most of the people got frustrated and dumped the car to get one with a factory 5spd
 

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Black 2001 RS
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783 Posts
I've seen a similar issue when the switch in the transmission for neutral was faulty. The ECU didn't quite know when to engage its idle control. The clutch switch worked, so when the clutch was in, it knew to idle the engine, but when the clutch was out and trans in neutral, it sometimes had a hard time. Might also try testing that switch.
 

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1998 Impreza 2.5rs
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35 Posts
Discussion Starter #16
The pin is grounded, as I recall when I didn't have it grounded on accident it threw a code for the trans. I never had this stalling issue when the previous owner had the heads out of whack, now that everything seems to be right it's stalling. I'm pretty sure it might be the IACV like previously stated I'm hoping to be going to pick a used one up today or try and clean mine.
 

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1998 Impreza 2.5rs
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35 Posts
Discussion Starter #17
Welp tried cleaning my IACV and putting on a different one still stalls but doesn't seem as bad could also be that I'm looking for it now. Also now it only stalls under heavy braking, tomorrow I'll go through all the wiring and grounds again and everything else.
 

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1998 Impreza 2.5rs
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35 Posts
Discussion Starter #18
Solved:Car dies randomly and under heavy braking

Thank you to everyone for the help and advicereally helped me figure this out and shocker the previous owner messed up the ground for the ecu when he manual swapped it. He put a connecter on the pin and it was too big to fully fit in the harness. So I pulled a the ground wire from a spare manual forester harnes I have( by the way, might be obvious to some but you can't use a forester harness on a 2.5 rs) to ground the pin and now it drives perfect, doesn't even drop past 700rpm. I can hopefully finally just drive it, and enjoy the 11:1 compression of the hybrid built engine.
 
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