[tmaghack]

I am trying to figure out why my boost falls below target and throws a 30FF. I followed the n54 diy on boost leaks and spliced a vacuum gauge in between the solenoids and only pulled 10" at wot. So I hooked up the vac gauge individually and idled the car and shut it off. The back solenoid held pressure until I disconnected the gauge. I did the same thing to the front solenoid and it would bleed off so I figured bingo I found the problem. Ordered a new boost solenoid and swapped them out and the new one bleeds out exactly like the old one. Has anyone had anything like this happen before? Any suggestions?

[1Spec]

Have you tried changing all your vacuum lines?

[tmaghack]

I have just visually inspected and listened for leaks. When I shut the car off and unplug the line coming from the vac pump I hear a rush of air so I figured it was holding.

[335NJ]

Replace the vacuum lines, boost solenoids won't hold vacuum if there's cracks in the lines.

The OEM lines have a fabric layer which covers the actual rubber/silicone vacuum line, making it hard to tell if they're actually cracked.

[whosdady]

Originally Posted by tmaghack

I am trying to figure out why my boost falls below target and throws a 30FF. I followed the n54 diy on boost leaks and spliced a vacuum gauge in between the solenoids and only pulled 10" at wot. So I hooked up the vac gauge individually and idled the car and shut it off. The back solenoid held pressure until I disconnected the gauge. I did the same thing to the front solenoid and it would bleed off so I figured bingo I found the problem. Ordered a new boost solenoid and swapped them out and the new one bleeds out exactly like the old one. Has anyone had anything like this happen before? Any suggestions?

Replace all of your lines. Also check the diverter valves and connections at the ic. My issue was at the ic.

[mike@x-ph.com]

Originally Posted by 335NJ

Replace the vacuum lines, boost solenoids won't hold vacuum if there's cracks in the lines.

The OEM lines have a fabric layer which covers the actual rubber/silicone vacuum line, making it hard to tell if they're actually cracked.

+1

[tmaghack]

I will replace lines this evening.

[335NJ]

Originally Posted by tmaghack

I will replace lines this evening.

Use lines rated for the high temps the turbos give off! Don't just use cheapo line.

[Odan.be]

BMW has two types of vac lines. I changed all my vac with the heat resistant type, like the ones that goes to the turbo's.
Front and rear nipple are a b*tch to get to, but it can all be done from the engine bay

[07335XI]

Originally Posted by tmaghack

I am trying to figure out why my boost falls below target and throws a 30FF. I followed the n54 diy on boost leaks and spliced a vacuum gauge in between the solenoids and only pulled 10" at wot. So I hooked up the vac gauge individually and idled the car and shut it off. The back solenoid held pressure until I disconnected the gauge. I did the same thing to the front solenoid and it would bleed off so I figured bingo I found the problem. Ordered a new boost solenoid and swapped them out and the new one bleeds out exactly like the old one. Has anyone had anything like this happen before? Any suggestions?

i had this problem when i had my turbos replaced. they swapped out the turbo solenoids and the boost problem went away