SR20 S13 Goes Rich, Lean, Rich

[nothinbuddadreamer]

Okay so I have a fairly stock sr, it’s rebuilt with around 5k or so on it,mls head gasket and arp head studs, I bought this engine off my buddy, barely put any miles on it since I got it in the car, I drove it when the engine was still in his car and it ran great, no hiccups, but now that it’s in my car it’s doing some weird stuff, it feels like it pulls timing at around 3000rpms and leans out. At WOT my afr’s are around 11:1 but at around 3000rpms it leans out to 13:5 -14:1 and stops pulling, like it just hits a spot and then as soon as it reaches around 4700rpms or so it richness back up to 11:1 and pulls hard as fuck all the way to redline, I have no vacuum leaks or boost leaks, all my grounds look good. I have a vent to atmosphere bov but that never effected it when it was in my friends car. My fuel pump is hard wired to a constant 12v with a relay, it’s an ISR 255, Injectors are deischworks oem replacements, so the stock 370’s or whatever the factory ones are rated at. Also the engine does idle pretty lean at around 17:1. If anyone could help me diagnose this that’d be great, it’s been a weird process, I’m thinking of adding a few more engine to chassis ground and seeing if that helps at all.

[nisileighty]

Check your cam angle sensor timing.
Check your TPS voltage.
Clean your MAF.
Clean your plugs.
Add more grounds.

[nothinbuddadreamer]

Check your cam angle sensor timing.
Check your TPS voltage.
Clean your MAF.
Clean your plugs.
Add more grounds.

Nothing should have changed coming from his car to mine, we swapped everything from his car to mine in a day, his timing was set at 15degress and the tps is solid, maf is solid, plugs are practically new and gapped correctly, but I’m definitely going to add more grounds, I think I only have one or two engine to chassis grounds

[5280VertDET]

Loose ground for the O2 or ECU or Coils?

[RomulanS13]

I had a bad alternator and it was causing all kinds of boost related issues. Under light throttle and or low boost drove fine but when i got on it it would break up no matter what rpm and would sound like a wrx but as soon as I let off a bit back to normal. I noticed my voltage output was lower than normal one day and I had a replacement alternator stashed away for these moments so I wouldn't have any down time it my daily driver and I replaced it and all of a sudden all my boost related issues are gone.

[nothinbuddadreamer]

Loose ground for the O2 or ECU or Coils?

I feel like if that was the case it’d be super inconsistent. And in my case it’s the same every time, the same rpms’s every time, it’s not like breaking up it’s like hitting a wall like it wants to go then hesistates, it feels like it just pulled all the timing away from it, I’m still making 10lbs of boost but with no power, even with it being lean the way it is it should still pull hard just not very safe lol. But I’m going to re check grounds tomorrow and add a few

[nothinbuddadreamer]

I had a bad alternator and it was causing all kinds of boost related issues. Under light throttle and or low boost drove fine but when i got on it it would break up no matter what rpm and would sound like a wrx but as soon as I let off a bit back to normal. I noticed my voltage output was lower than normal one day and I had a replacement alternator stashed away for these moments so I wouldn't have any down time it my daily driver and I replaced it and all of a sudden all my boost related issues are gone.

This isn’t like breaking up though, it just hits a big hesistiaion like it pulled away a bunch of timing and went super lean and then after it hits 4500rpms or so it roars to life again and pulls hard as fuck

[5280VertDET]

I feel like if that was the case it’d be super inconsistent. And in my case it’s the same every time, the same rpms’s every time, it’s not like breaking up it’s like hitting a wall like it wants to go then hesistates, it feels like it just pulled all the timing away from it, I’m still making 10lbs of boost but with no power, even with it being lean the way it is it should still pull hard just not very safe lol. But I’m going to re check grounds tomorrow and add a few

True, my best 2nd guess is bad ecu or alternator isn't giving the right voltage (either it's bad, loose connections or loose belt). do you have a voltmeter or gauge in the car?

[wedscvr]

I experienced something very similar and ended discovering the grounds attached to rear of the intake were loose.