MHD and BMS intake

[Monkeypoop]

I have been running MHD OTS stage 2 and 2+ for sometime and recently I have been getting a idle lean situation (since most recent MHD updates and Full writes). Does anyone know if I need too have a custom tune to resolve it or do you think I have a leak further down from MAF? I inspected for vacuum leaks and checks the valve cover already for any issues. Cleaned MAF & MAP sensors. Came back with nothing…. 2017 N55 (ER catless down-pipe, bms intake setup, VRSF intake tube, xHP Tran tune)

[Clifton]

Sounds like you have a leak. Unmetered air is entering the intake that was not accounted for by the MAF.

A thorough check of all hoses and intake components is required. Google for a few ideas on testing and diagnosis methods; like small bursts of brake cleaner causing RPMs to rise.

[Monkeypoop]

I'll give the brake cleaner bursts a whirl… like I said I inspected and double checked the upper intake down to the bottom air duct off the passenger side down to the coupler to the turbo. Is there any other spots to check? Is it possible I have a bad MAF or pressure sensor? I have watched YouTube videos and looked at every forum post with a N55 engine and similar codes. I did notice that my N55 does not have a vacuum hose going from the passenger side valve cover. It was a place to check for a bad valve cover when oil collects in this video:

[Monkeypoop]

MHD came back and said it's a known issue with aftermarket intakes and try OE. Also to double check O2 sensors for leaks or issues.

[Monkeypoop]

update: most of the codes did not point to it but it was the top O2 sensor on the Downpipe that was bad. I also went ahead and changed the MAF and oil fill cap for giggles.

[sukhk527]

interesting to know the lean code was a bad O2 sensor. might buy a new maf as part of turbo upgrade just to be on the safe side.

[Monkeypoop]

I initially did not have any codes relating to O2 sensor. It popped once, cleared and went on my way. Turns out now the shifts are much less radical and it’s a dream. That’s with stage 3 xHP tune. Didn’t realize how much the pre-cat affected the AFR enough to cause shifts and the stuttering I experienced. Education under fire. But good to know nonetheless.

[lonestar22]

the N55 does not like intakes very much. even with a tune they will throw codes. Your best bet is a custom tune to account for the extra air coming in from the intake.

[sukhk527]

Originally Posted by lonestar22

the N55 does not like intakes very much. even with a tune they will throw codes. Your best bet is a custom tune to account for the extra air coming in from the intake.

Agree, custom tuning allowed me to adjust fuel trims to compensate. still don’t like the idea of it though sometimes lol

[Monkeypoop]

Any recommendations of a tuner for MHD?

[sukhk527]

Originally Posted by Monkeypoop

Any recommendations of a tuner for MHD?

WOT808 is my tuner. Been working with me on multiple setups on the car for over a year to great success.

[N1ck]

Funny, just last weekend I made a post on the Facebook pages.

I have a catless DP, NGK gapped plugs and chargepipe, stock air box. Been running stage 2+ for 3 months and close to 5,000 kms with no issues, it’s been great. I pulled all those lean codes as well and flashes to stage 1 for right now, haven’t pulled any codes in the last few hundred miles. I emailed MHD and they said I must have a leak somewhere.

Did you eventually get an o2 sensor code? Curious how you found that…

[Monkeypoop]

Originally Posted by N1ck

Funny, just last weekend I made a post on the Facebook pages.

I have a catless DP, NGK gapped plugs and chargepipe, stock air box. Been running stage 2+ for 3 months and close to 5,000 kms with no issues, it’s been great. I pulled all those lean codes as well and flashes to stage 1 for right now, haven’t pulled any codes in the last few hundred miles. I emailed MHD and they said I must have a leak somewhere.

Did you eventually get an o2 sensor code? Curious how you found that…

I sent datalogs, error codes and a list of mods to MHD. They first said it was BMS intake… so I removed it and cleared the codes with no changes. Then after that they said it is a vacuum leak past the MAF or around the O2 sensors or Exhaust. I initially blamed the recent update to MHD, because I have been running Stage 2+ since I got it over a year. I also posted to spool street and no bites, but in their forums I saw some issues that related to the pre-cat O2 sensor. So between MHD and forums I figured I’d try the cheaper options to fix first versus looking at Valve Cover or any other major related Air Lean causes. Hope that helps.

[sukhk527]

I’ll add one more thing. If you keep getting it, just do yourself the favor and do a smoke test from the intake. I had to do the same after chasing the same code for a while and it turned out I had a hairline crack in my turbo to IC pipe. this was last winter.

[Monkeypoop]

Originally Posted by sukhk527

I’ll add one more thing. If you keep getting it, just do yourself the favor and do a smoke test from the intake. I had to do the same after chasing the same code for a while and it turned out I had a hairline crack in my turbo to IC pipe. this was last winter.

Good call, forgot to add that I did inspect everything from chargepipe to catalytic converter.