How does the Brake Booster Solenoid work?

[fattycharged]

Long shot...something to consider as a possibility. Could be an ECU issue. Randy at Epic would be my go to if you go down that road. Not sure if you're there yet...I need to see more desperation in your posts before I'd recommend trying that...lol

Not quite there yet…we'll see next week


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[bigjae46]

Agreed. No new tune. Yes, I've been in there the past few days, I decided to change out the MAP sensor and wiring, which was resolved for now.

For clarity, I can connect to the tool to pull codes through BMW function, just not through the OBDII function, which I had seen before, its intermittent and I did not have a trickle running on the batt.

I'll try to connect next week through my laptop, need to install parallels, pull some logs


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Long shot...something to consider as a possibility. Could be an ECU issue. Randy at Epic would be my go to if you go down that road. Not sure if you're there yet...I need to see more desperation in your posts before I'd recommend trying that...lol

[fattycharged]

Did you recently install a tune? Any work in the ECU box?

The fact that you can't connect with the scan tool is suspect on its own and may indicate an issue on the ECU side…

Agreed. No new tune. Yes, I've been in there the past few days, I decided to change out the MAP sensor and wiring, which was resolved for now.

For clarity, I can connect to the tool to pull codes through BMW function, just not through the OBDII function, which I had seen before, its intermittent and I did not have a trickle running on the batt.

I'll try to connect next week through my laptop, need to install parallels, pull some logs


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[eacmen]

unplugged booster, only slight change.
fuel trims I don't know, my Foxwell decided it won't connect in OBD today, yesterday no issue.

yes, used smoke tester to find air rail leaks. all good last check

also throwing both pre cat faults it seems.

going to have to put this to rest till next week unfortunately, leaving town tomorrow evening, but looks like I have some work to do before this thing goes on it's first born-again journey


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Did you recently install a tune? Any work in the ECU box?

The fact that you can't connect with the scan tool is suspect on its own and may indicate an issue on the ECU side…

[fattycharged]

sounds like it might be a vac leak from the booster or failed check valve

pull the valve from the booster and cap the valve to see if your engine idle improves.

what are the fuel trims?

do you have a smoke tester?

unplugged booster, only slight change.
fuel trims I don't know, my Foxwell decided it won't connect in OBD today, yesterday no issue.

yes, used smoke tester to find air rail leaks. all good last check

also throwing both pre cat faults it seems.

going to have to put this to rest till next week unfortunately, leaving town tomorrow evening, but looks like I have some work to do before this thing goes on it's first born-again journey


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[eacmen]

I will give it a shot, but I think I have tried that. Valve clicks with key in start position when I unplug it and plug back in, so I assume functional.
After clearing up vacuum leak at the air rail and almost completely at the MAP sensor (still a small leak...) I still have idle issues, engine is running rough after cold start cycle, it gets worse when I hit the brake pedal.

sounds like it might be a vac leak from the booster or failed check valve

pull the valve from the booster and cap the valve to see if your engine idle improves.

what are the fuel trims?

do you have a smoke tester?

[fattycharged]

Have you tested solenoid between the booster and intake manifold. Maybe unplug it and see if the brakes stick on if you rev the motor.

I will give it a shot, but I think I have tried that. Valve clicks with key in start position when I unplug it and plug back in, so I assume functional.
After clearing up vacuum leak at the air rail and almost completely at the MAP sensor (still a small leak...) I still have idle issues, engine is running rough after cold start cycle, it gets worse when I hit the brake pedal.

[bigjae46]

Have you tested solenoid between the booster and intake manifold. Maybe unplug it and see if the brakes stick on if you rev the motor.

[fattycharged]

No dice...no more noticeable vacuum leaks after new air rail o-rings, but no brake booster either.

[fattycharged]

should get it fired back up tonight and will update on booster function


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[fattycharged]

Still interested if fixing the vacuum leaks resolves the brake pedal issue.

I've got a local hydraulic supply shop I am going to stop by to see if they can supply them, otherwise I won't have them till next week through ECS


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[jayjaya29]

Still interested if fixing the vacuum leaks resolves the brake pedal issue.

[fattycharged]

6 looks noticeably bent to me…


found my culprit on 6

and 3


sorry yall, realize i've turned this thread into my journal…


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[fattycharged]

$50 Amazon purchase worth its weight. MAP sensor leaking heavily and the other main culprit is AT injector 6 on the rail, pouring smoke.

So for future anyone having this issue, haven't solved it quite yet till I pull the rail and figure out what to do with this MAP sensor. I did try and replace the o-ring on the MAP already with no luck, likely too small but all i had lying around from a shock rebuild.

I'd post a video but don't know where to host quickly



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[fattycharged]

Ok messed with it today again...

With the booster open to atm and engine running, with check valve capped, still have an unstable idle and throw a DME intake man pressure fault.
Removed the jet hose entirely from the fuel rail and no real noticeable leak with the blow/suck test.... So either I have a leaky booster that doesn't leak vacuum, or there is a leak in the jet valve line, or something else I'm not thinking of? I cleared the code multiple times and even engine off the code is thrown....I also swapped out the cheap MAP sensor and wiring with one of the kits from Covid, so possible that is throwing the code, either way it was present prior to that, along with lean mix

Ordered a booster to have on hand for install once I pressure test the vacuum with my latest Amazon purchase of a smoke tester and caps.