Overboost, misfires, AFR all over the place

Also make sure that the intake and any intercooler couplers don't have small tears that would only open up when the motor twists

But I agree with enki honeycomb air straightener would be my next step

 

Before you do, post a pic of your intake. Filter off, down the pipe so we can see what's going on in there.

 

No

 

Hey! Sorry for the long time without a check in, I have been out of state for a little and just got back. Drove the car today for the first time in over a week to go to work and noticed that car idles very rough at cold start, surging up and down.

Drove the car and it hesitates at around 4k RPM and goes into boost (only to 11-12PSI instead of the normal 19-20PSI) and makes a lot less power when boosting.

I was coming to a stop and put the clutch in and put the car in neutral and the RPM's seemed stuck at around 2000 rpm until I came to a complete stop. (This seems to go away If pressing the clutch in while in gear I think, but would need to replicate more to be sure). Also noticed that HPFP pressure drops to around 330 sometimes when the engine sticks like that, but seems normal when driving (900-1400 when driving normally, but only hitting like 1800 at WOT, and idling right around 420 when stopped.)

Any idea what's going on here? I feel like maybe a boost leak that's gotten way worse? Something else?

I have yet to resolve the misfire (although ECU seems to have adapted to it so it's not so obvious) since I have been out of the state, but plan on checking a bunch of stuff including coils this weekend. Might go for a smoke test at an actual mechanic to see if I have a boost leak somewhere.

Any input is greatly appreciated. Thank you!

 

The rough idle at cold start can be normal if your VCTS is disabled or missing (non stock intake manifold will do it, or modified stock).

Rev hang can be caused by a check valve sticking open in the PCV setup if you have a hose going from intake mani to intake. With that port on the intake mani capped off, the symptom would be opposite (car stalling out when going clutch in on decel)

HPFP pressure dropping to even the 200s when unloaded is nothing to worry about; pretty normal; only need to care about idle, WOT, and in between really.

 

Understood, although these are all new developments. Anything I should be checking/what would I need to do about the stuck check valve?

Also, would that explain not being able to build full boost?

I think I will do another not so janky boost leak test as well just to be sure.

 

If you know where the check valves (might be more than one) are in your system this should be easy. Just pull them out and check them/spray them out with carb cleaner or something. Some check valve can be disassembled for easier cleaning.

It is a viable cause, yes.

Safe bet.

 

Sorry for the late check in. Fixed the problem, found a boost leak and replaced the hose, and car seemed to run fine for a bit. Today while idling at a light the car made like almost no power and stalled when trying to go when the light turned green, and when turning the car back on, the traction control light was on, and the car still made barely enough power to get to the side of the road. Turned the car off, turned it back on again and it drove fine for another few minutes before happening again at another light, and a few times after that. Turning the car off and back on again made it drive fine for a little each time. Checked for CEL's and this came up:

P0638: Throttle Actuator Control Range/Performance (Bank 1).

I also noticed the dash lights and radio in my car die and run back on for a split second a few times while driving today.

I assume I should clean out my TB, clean connectors. Anything else I should look for?

This is turning into a never ending list of things to fix lmao.

Thank you!

 

Take it to an auto parts shop and have them test the alt and battery.

 

Will do, thank you again sir.

 

Check that the battery cables are tight and not corroded

 

Did you ever fix this?

 

Probably. He didn't come back after he got the advice.