off_set

Hey guys, working on the turbo and I recently upgraded to the IPD plenum and the larger throttle body. Install went smooth for the most part but now every time I get into boost I breaks up really bad .

I have boost leak tested it and have fixed all the little leaks
i have no check engine lights for a misfire

went through and double checked that everything was plugged in and we’re all good

the car is tuned, I’m unsure of which programming it has.

I am out of ideas at this point, it was running strong before this

any ideas as to what to trouble shoot next before it go back to stock and sell this plenum

2fcknfst

You have a leak that isn't presenting itself until it is under sustained load. I had a similar issue and it turned out to be a hose that had a tiny little split in it - once that was identified, corrected and tuned, it's been gravy ever since.

kamlung

when you plugged all the hoses back, did you zip tie them to ensure they wouldn't leak?

Scrh1

I feel your pain…just went through this while doing an alternator and pulley upgrade. Link to my thread here:

https://rennlist.com/forums/996-turb...-belt-etc.html


look at the last link in my post on tips for the plenum install and sealing up that connection. I will say drop the motor, boost leak test to 20lbs + and that hose will likely pop off. Replace any hoses and zip tie everything possible. It was most frustrating ……and took the 4th try before I had it seated properly and it wouldn’t pop off at full throttle 3rd gear pulls. Stay close to home and bring gloves and a good set of flexible nut drivers for when the hose pops off under boost on a test run. Good luck and happy to answer any questions I can. Thx - scrh1

off_set

Some , most of those are vacuum I would assume and not under huge load , probably why they were never secured from factory

I wouldn’t think a small leak would cause it to just fall on its face when any type of heavy load is applied , I’ve tried it with maf unplugged S well which made no change.

any common things I should go back and over look

could it be plugs and coils ?

2fcknfst

If you had a mis fire, plugs or coils, it would throw a code.

Carlo_Carrera

Plugs and coils have nothing to do with this. He replaced the Plenum and somewhere in that process something went wrong. Concentrate on the Plenum.

2fcknfst

Look at #5...

Carlo_Carrera

He changed the Pelham and is now getting misfires. The Pelham is the problem.

2fcknfst

Got that, but then he asked if it was plugs and, or, coils, to which I responded it would throw a code if it was....

off_set

thanks for all the tips guys. I figured it wasnt plug/coild related as there are now misfire codes. I'm coming from the b5s4 world and familiar with chasing down boost leaks, usually doesn't cause such a huge stumble like this so i assumed ignition or fuel related.

for those that have replaced the plenum, how did you ensure that couplers were well seated on the back side of the plenum and make sure its clocked correctly for the y pipe and throttle body to align? I dropped the motor for initial install, figured out it had to be lifted back in place before connecting intercooler hoses. with it all back in original location it is tough to get back there to make sure everything is correct.

wross996tt

If there are misfire codes, then likely coils/plugs. Correlation is not necessarily causation.

off_set

No codes, i think we have ruled out ignition/coils at this point

Carlo_Carrera

As I suggested the cause of the problem is the plenum or something to do with the installation of the plenum.

Carlo_Carrera

if the car ran fine with the old plenum and is now misfiring with the new plenum the plenum or the install of it is the problem.