Rough idle, Lean AFR

Hey guys so here’s the deal, something’s going on with the speed, but I’m not sure what it is. I’m getting an intermittent vacuum leak, that causes a lean status. While driving, there’s no issues. It only occurs are idle or when stopped.

I will add that when the AC compressor turns on, it also happens, but it also occurs with the AC off.

So, let’s here’s some ideas of what could be causing this problem; happens at idle and sitting still.

1. Purge valve - replaced
2. Pressure relief valve on fuel rail?
3. PCV is new as of October 2023
4. All my vacuum lines (silicone hoses, most if not all are direct and have no breaks or joints to mitigate leaks) are running through my JMF manifold; PCV valve to OCC, then to intake, BOV, purge valve, brake booster, MAP.

I will post some logs shortly with a capture of what’s happening.

Thank y’all for the help, happy holidays

 

Have you done a boost leak test? Yes it matters even at idle, have you cleaned your MAF sensor and inspected it's oring? What intake / mods do you have.
@Enki if I recall correctly isn't the AC on vs off causing the issue a dirty air filter in your experience?

 

I have not performed a boost leak test, yet. Currently on orders for the weekend. But on the to-do list. The MAF was cleaned and new o-ring installed when I did the DM intake. Below is a list of all the modifications I have done.

1. BNR s4 (11/25/2023)
2. Bosch 3 Bar MAP (11/25/2023)
3. XS Power tubular exhaust manifold (11/25/2023)
4. DM 3.5” Aluminum Intake (11/25/2023)
5. Damond Motorsports PCV Plate
6. Cobb 3 Port EBCS (11/25/2023)
7. CNT down-pipe / 3” exhaust
8. JBR OCC w/ VTA (08/25/2023)
9. JMF Intake Manifold w/ vacuum distribution (11/25/2023)
10. EGR delete (8/2023)
11. Tune by Will @ Purple Drank Tuning (in progress)
12. Serviced fuel injectors w/ Overspeed Seals @ CWTurbochargers (10/2023)
13. HPFP Internals (8/2023)
14. Valve Cover VTA with filter
15. BOV - VTA on hot side of Intercooler piping (Unknown brand, currently working with Tuner to identify and see if that’s causing issues)

 

Yeah boost leak test asap and check air filter if it's dirty it can cause issues iirc (waiting for enki to confirm hence my tag of him earlier).

 

I’ll check out the air filter, it should be clean, it’s only been being used less than 2 months. I’ll get the boost leak test done as well, and return with results.

Additionally, would any fueling areas be of concern? O2 sensors on back of down pipe throwing off AFR? Fuel pressure relief on fuel rail?

I’ve had vacuum issues prior but they were very apparent and easy to find/fix. This is a new one for me.

 

You could check the PRV with the engine hot as well as the hpfp ground,

the AC on vs off is a telling sign I just don't recall for what, do you have a air straightener or honey comb in your intake? Something like this
https://www.treadstoneperformance.com/honeycomb-maf-mass-air-meter-airflow-straightener/p103828 as that can affect flow on MAF especially at idle

 

Copy. I will do the PRV test later as well. To the air straightener, no, it the wide open 3.5” aluminum pipe with the massive cone on the front from DM. No further alterations were made. Used the supplied O-ring for the MAF.

Greatly appreciate the input, making a list of checks to do after this weekend is concluded.

 

Additionally, this is my single can can set up; PCV to OCC to Intake manifold. The OCC is VTA but with a check valve just under the filter. There is a check valve inline going to the intake manifold. Not sure if that matters. It’s been perfectly fine up to this point, but I’m not ruling anything out.


Sent from my iPhone using Tapatalk

 

I don't give a shit what anyone else tells you; this is a huge issue for a daily driven car. Get the Treadstone honeycomb sized right for your intake, CRUSH the outside just enough in the parts that protrude so it fits very snugly and press it in. You don't need to glue it or anything at all, as long as it's in there tight it won't go anywhere. You also don't need to worry about the outside edges being messy; its the inside that you need to make sure is perfect.

This is what mine looks like and has been working perfectly for at least 8 years:



No welding, no glue, not moved a mm since I installed it. Note how the outside is fucked up in some parts; this is fine and won't hurt anything.

 

Thanks @Enki !

 

Perfect. Thank you, I will do this immediately. Where can I find that honeycomb?

 

Scroll up. Awa linked it.
Edit: Don't cheap out and get larger cell size from somewhere else, the smaller size that Treadstone sells is what you want.

If you want to know why, look up videos on laminar flow and how people make them with soda straws and shit.

 

My apologies, didn’t see the link before. Just started using the app vs webpage. Still getting use to the interface.

@Awafrican @Enki thank you both, I’ve ordered the Treadstone honeycomb from that link, in addition to a few other things; HPFP rebuild kit, check valves to have on hand. I will update this thread when everything I do and find and once a solution is found, I’ll post that too. Thank you!

 

Happy to help, how'd the boost leak check go?

FYI use @ to mention a user name just @username and it'll even show the user name options as you spell it. Edited your post

 

Hoping to get the boost leak test done today. I’ve been away doing army crap for the last several days.

 

@Awafrican so pretty sure I found the leak, right on top of the intake pipe. Not something I like to admit, but mistakes must have been made. The MAF o-ring was broken and the screws loose. Not sure how that was missed or happened but it’s fixed now.

But I have another question, I have a BNRs4 and it’s been smoking at idle and low rpm since install about 3 weeks ago. Smells like oil. Heard some folks say they talk to Brian or Bryan at BNR and got some results. So I called and spoke with him about the turbo smoking. Asked if I had a catch can, yes. I have the DM pcv plate, pcv valve to the can then to the intake manifold (with check valve between can and manifold). The can is/was VTA and he said instead of VTA, run the vent line to the intake pipe, gave the a shot. No more smoke, at all. BUT, the car now idles around 1100rpm (regular is 800rpm-ish) and fluctuates with the turning of the steering wheel and just seems like something is very off. I don’t like it but then again, I’m not expert and this is my first time going this far on modding and doing things with the car.

 

The higher idle is because you're bypassing the throttle body with supplemental fresh air.

 

@Enki so, this is bad? Sorry if I’m not fully understanding. First time going this far with the modifications and tinkering. Is this bad? Or something I need to notify my tuner on? Or what should I do? Thank you for any input.

 

Not bad. I've targeted an 1100 idle in my tune.

 

so what about the idling bouncing around when moving the steering wheel? And AFR kind bouncing during and going from a stop? Assuming where you said it’s in your tune, I should tell my tuner ?