JCW airbox issue

MiniGB06 · #1 01-30-2009, 07:46 PM

Hi all,
This is a question regarding my boss's car. He has a real sweet JCW MC40. Recently, the secondary flap on his airbox stopped working. We found that it was due to a disconnected air hose running from a y-junction connector hooked into the vacuum system. Even with the hose reconnected we can't get the flap to open at 4500 rpms.

Can we remove the flap without any damage to the filter system? Are there any concerns about rain getting into the airbox? What's the easiest way to remove/bypass the flap system?

Thanks!

blu jcw · #2 01-30-2009, 08:14 PM

Many peeps with the JCW air intake remove the flap without negative results. I have not removed it. I believe it just pops out, and it can always be reinstalled.

Search this site for the filter change/installation thread, I remember it containing information about removal.

minimarks · #3 01-30-2009, 08:32 PM

The vacuum line is probably just pulled loose inside the box.

tazio · #4 01-30-2009, 09:32 PM

Just rip out the flap as well as the plug on the hole just below it. If you get one of these, that lower hole is aimed straight into the open end of the filter.

Make sure you plug/cap the vacuum line, though.

quikmni · #5 01-31-2009, 08:31 AM

Here is a link to the Mini-Madness JCW filter installation but it also includes options of modifying the flap. The main thing is that the instructions provide many pictures that will help you see the various parts of the airbox so that you might be able to repair the current airbox/flap.
http://www.mini-madness.com/pdf_file...structions.pdf
I removed my flap and all associated hardware with no problems after 30,000 miles.

MiniGB06 · #6 02-19-2009, 03:00 PM

Thanks, quikmni. That did the trick.

Affliction35 · #7 02-23-2009, 11:22 AM

Quote:

Originally Posted by quikmni

Here is a link to the Mini-Madness JCW filter installation but it also includes options of modifying the flap. The main thing is that the instructions provide many pictures that will help you see the various parts of the airbox so that you might be able to repair the current airbox/flap.
http://www.mini-madness.com/pdf_file...structions.pdf
I removed my flap and all associated hardware with no problems after 30,000 miles.

I have removed my flap but now every 60 or so miles my Service Engine light comes on, and goes back of after restarting car several times. Step three on the diagram suggests to remove the electrical connector and not to reinstall. I reinstalled mine after the mod could this be causing the Service Engine light.

BlimeyCabrio · #8 02-23-2009, 11:45 AM

You need to read the code that's causing the SES to have any clue what's causing it. Your local auto parts store should be able to read the code for you...

Affliction35 · #9 02-23-2009, 12:40 PM

Quote:

Originally Posted by BlimeyCabrio

You need to read the code that's causing the SES to have any clue what's causing it. Your local auto parts store should be able to read the code for you...

I had the code read and it came back with: P1237 : Secondary Upstream Manifold Air Pressure Sensor Low Input, which leads me to belive that it has to to with the CAI. And it happened right after the CAI mod.

BlimeyCabrio · #10 02-23-2009, 01:22 PM

It's doubtful that has anything to do with your CAI. That's a code from your MAP sensor... which doesn't have anything to do with the airbox... sometimes the MAP sensors just fail.

quikmni · #11 02-23-2009, 01:40 PM

Did you plug the vacuum line with a screw or cap? Maybe there is a slight vacuum leak where you plugged the line.

Affliction35 · #12 02-23-2009, 01:55 PM

Quote:

Originally Posted by quikmni

Did you plug the vacuum line with a screw or cap? Maybe there is a slight vacuum leak where you plugged the line.

No, we pluged the vacume line back into the box and the electrical plug. We did this at a dealership with help from a tech, and he made sure everything was hooked back up. I will plug the hose and remove the plug and see what happens.

minimarks · #13 02-23-2009, 01:59 PM

Had that same code and it was caused by the vaucuum line from the airbox being crack (by a mini mechanic) at the motor. A smoke test is the best way to find a vacuum leak. I was about to replace the map $ensors until I went ahead and got a smoke test done saving me some cash in the end.

Affliction35 · #14 02-23-2009, 02:48 PM

Quote:

Originally Posted by minimarks

Had that same code and it was caused by the vaucuum line from the airbox being crack (by a mini mechanic) at the motor. A smoke test is the best way to find a vacuum leak. I was about to replace the map $ensors until I went ahead and got a smoke test done saving me some cash in the end.

Thanks, I bet it is that vacume hose either leaking (pulled of when doing MOD and had trouble getting it back on) or that it need not be there post MOD. I'll try to plug it tonight and let you all know how it works out. Thanks for the help.

Affliction35 · #15 02-23-2009, 02:52 PM

Quote:

Originally Posted by BlimeyCabrio

It's doubtful that has anything to do with your CAI. That's a code from your MAP sensor... which doesn't have anything to do with the airbox... sometimes the MAP sensors just fail.

The car only has 24k on it. And it would be unusual for a MAP sensor to go out at that milage.

minimarks · #16 02-23-2009, 02:59 PM

Quote:

Originally Posted by Affliction35

Thanks, I bet it is that vacume hose either leaking (pulled of when doing MOD and had trouble getting it back on) or that it need not be there post MOD. I'll try to plug it tonight and let you all know how it works out. Thanks for the help.

Follow the small line coming from the airbox towards the motor, there will be a tee there for it to plug into. from there the vacuum runs to the by-pass valve, there is where mine was cracked. A few inches of hose and the problem was fixed. You will need to get the code cleared as it will not clear itself.

BlimeyCabrio · #17 02-23-2009, 04:47 PM

Those hoses stretch out with age & heat, too... mine got loose on the fittings after a while...

Affliction35 · #18 02-26-2009, 11:16 AM

Quote:

Originally Posted by minimarks

Follow the small line coming from the airbox towards the motor, there will be a tee there for it to plug into. from there the vacuum runs to the by-pass valve, there is where mine was cracked. A few inches of hose and the problem was fixed. You will need to get the code cleared as it will not clear itself.

I plugged the hose and removed the electrical wires put a 100 or so miles on Fitz'y and everthing is working great no SEL. But one question when you said follw the hose out of the CAI to the three. What is the other hose comming of the tee. Mine has a approx 2" hose comming of the right side that is not plugged into anything. Should it be? I could not seem to find a place where it would plug in.

BlimeyCabrio · #19 02-26-2009, 11:37 AM

That's probably a big part of your problem... the other side of the T plugs into the bypass valve... if it's not plugged in, the bypass valve is always closed... good for performance, bad for MPG...

It's also possible it just got pulled loose while you were working on it... as the hose gets older it stretches out and pulls off the nipple more easily... helps to replace the hose.

That hose being disconnected could be a reason for throwing the MAP code in the first place...

Affliction35 · #20 02-26-2009, 12:50 PM

Quote:

Originally Posted by BlimeyCabrio

That's probably a big part of your problem... the other side of the T plugs into the bypass valve... if it's not plugged in, the bypass valve is always closed... good for performance, bad for MPG...

It's also possible it just got pulled loose while you were working on it... as the hose gets older it stretches out and pulls off the nipple more easily... helps to replace the hose.

That hose being disconnected could be a reason for throwing the MAP code in the first place...

Well the hose on the opposet side is pluged in but, the hose just to the left (standing in front of the car looking down) is not pluged in. If that is the one you are talking about mine is apprx 2" long and seems to not have anywhere to plug in. Again thanks for your help. I put another 50 miles on him today with no SES light so I'm thinking that plugging the first hose has worked. Just wondering about the small hose. It does not seem to be causing a problem right now. But I will watch my MPG's.

BlimeyCabrio · #21 02-26-2009, 01:58 PM

If we're thinking about the same hose, then yeah.

For a standard installation of the JCW airbox, a T is inserted into the short (about 6") loop of hose for the bypass valve. The longer end of this is attached to a nipple on the intake tract below the BPV. The short end of this plugs into a hidden nipple in the black cap on top of the BPV, and is actually what makes the BPV open and close. The hose to the JCW intake plugs into the third leg of the T. if you have a little 2" piece of hose, it's most like the piece that plugs into the BPV itself... look at these instructions...should help to understand:
http://motoringfile.com/files/JCWUPGRADE.pdf

It's hose "4" on the last pic on page 6.

**Tsiggy** · #22 03-31-2009, 11:06 PM

I am getting ready to install the JCW air box in a stock mcs, do you guys mind answering any questions that I might have as I get ready to install? The electrical is what I am most concerned about getting right and the vacuum tips in this string have me thinking about been careful while i work in those tight spaces w/ those hoses. Thanx in advance. Tsiggy

BlimeyCabrio · #23 04-01-2009, 10:19 AM

If you *exactly* follow the instructions in the pdf I linked to above, you shouldn't have any questions.

But I'll answer any you have.

**Tsiggy** · #24 04-06-2009, 12:01 PM

I want to thank you all for this thread...great help! The JCW CAI had arrived while I was on a work trip so I didn't have any chance to rush into trouble. Reading this and other threads helped me immensely. By the time I was ready to do the install (my first day off) I knew where to find the bypass valve and vacuum hoses, how to find the one and only white with red wire and lastly where the #8 connection is on the plug at the fuse box. Hardest thing was fitting my hands under the intercooler to fidget the vac hoses into place. 4500 rpm comes and the Supercharger whine kicks in . The motor sounds happier at all rpms though, and it definitely sound a little more growly at 4000 rpm while cruising in the power range. I like not having the high pitch sound all the time too.

One last question: I left the plastic disk in the lower opening, closing it off as per the instructions. I did this because on Realoem that part is shown and called a "Sound Flap". Was I correct in leaving it closing off the port or is that an option?

Thanks again,
Tsiggy

BlimeyCabrio · #25 04-13-2009, 07:50 AM

You can run it either way. Leaving the disk in preserves the low-RPM sound muffling of the airbox. Taking it out will make the sound more pronounced at lower RPMs when the flap is closed. If you have a throttle whistle, removing the disk will make the whistling more pronounced. If you don't have the whistle, then you probably won't notice much difference with it removed. The engine gets plenty of air either way.