Help me fix my high idle and no power brake issue?

[540ig5]

'86 325es 5spd.

Just replaced the valve cover gasket, cleaned the ICV, adjusted the valves, replaced the master cylinder (with one from an e28). I also had the brake booster unbolted in an attempt to replace that as well, but could not wiggle it out of the engine bay, so I left it as is and bolted it back in.

After putting everything back together, my idle speed is at 1500rpm. I also have no power brakes, pedal stays firm with the car running. If I disconnect the brake booster vacuum line, the engine stalls out. When I plugged up the vacuum "port" for the booster with my finger, the RPMs stay at 1500rpm.

P.S. I did not have any of these issue before doing this work.

I'm kind of lost as to what to check next. Any advice would be great.

[efficient]

Vacuum leak somewhere

[Das Delfin]

brake booster vacuum leak

[540ig5]

Is there a way to test if that's the problem? Also, why do my rpm's stay at 1500 when I plug the vacuum booster port on the intake manifold? Shouldn't the rpm's get back to normal if my issue is a brake booster as plugging up that hole eliminates the booster from the equation? I'm just trying to understand what's what.

[MrBurgundy]

If the tps takes a dump it will idle high like that


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[Das Delfin]

yes there is a test. Lack of power brakes = booster vacuum leak. If your booster can't hold vacuum pressure, it won't work and you won't have power brakes

[540ig5]

yes there is a test. Lack of power brakes = booster vacuum leak. If your booster can't hold vacuum pressure, it won't work and you won't have power brakes

Makes sense. Any idea what could have went wrong? What should I check to fix it? It was working without fault before I messed with it.

[TimeMachinE30]

Locate brale booster. Place eyes upon vac hose at brake booster. Commence inspection for leaks. Very short distance. Could be a bad check valve, check valve on the wrong way. Tear in hose. Bad connection.

[atldohc]

when you changed the master, did you check the seal at the end of it that goes between it and the booster? if its damaged or missing, then you'll have a vacuum leak and little to no brake assist

[540ig5]

I'll check all that out. However, from my understanding I can eliminate the booster being the source of the leak by just capping off the vacuum inlet at the manifold? Is that not an accurate assumption?

(P.S. I tried doing this already and the issue has not gone away.)

[digger]

yes, if you block the leak at the Throttle body (some also goto the bellows) from the booster then you might have another leak somewhere if the idle doesn't change. othwerise could be bad ICV, throttle switch or you disturbed something by accident

[540ig5]

Solved. (at least half way).

The idle issue was due to a bad ICV. Turns out that the ICV was faulty as long as I've owned the car (5 years). To deal with the bad ICV someone along the way had introduced an "artificial" vacuum leak into the system. This was done by removing the cold start valve gasket and only using 2 screws to secure it to the intake manifold. When I was doing my valve cover gasket I installed the missing cold start valve gasket and the missing screw. This in turn sealed the vacuum leak and made the ICV fault "re-surface". I swapped for another used ICV i had laying around, and bingo, all is well. It's worth mentioning that the bad ICV did pass the resistance test as well as putting a 12v charge directly to it so see if the valve opens and closes. Even though it passed those tests, I guess it still was not able to properly regulate the airflow. I am still having the power brake issue, but that's just a coincidence and is a separate issue after all.