I have an 89 BMW 325i that I absolutely love and hope to have for years to come. I have owned Ernie for about 3-4 years now, and I have had to put in quite a bit of work into him. In the 3-4 years I’ve had Ernie, a funky thing has happened about 5 times now, which really worries me. I will be stopped in traffic or at a stop light, with my foot firmly on the brake pedal. Ernie starts rumbling slightly, and then it will do something that feels like a hiccup or something, and Ernie feels like he wants to lurch forward and my foot raises slightly off the brake, and when I catch it, I quickly push back down on the brake and all seems ok. This worries me quite a bit, and I’m not sure what, if anything, should I try to check on with the mechanic?
You should have a check valve between your intake manifold and your brake assist. Take it out and clean it in dishwater, or replace it. The irregularity in your idle is annoying and something that you probably want to resolve at some point, but it should not affect your brakes. The fact that the idle hiccup affects your brakes worries me. It means that if your car dies altogether for any reason, you will instantly loose all brake assist.
Actually, if he has a leak at the check valve it could also be affecting his idle. It’ll be felt by the engine as a vacuum leak.
Good call, by the way.
Thanks so much for your suggestions. I’ll take Ernie in and get the check valve checked out asap. Thanks!
OK, pop the hood and look for an “L” shaped approx 3" diameter black hose with rings around it. It’s a hose that air goes through on its way into the engine. With the engine at idle, grab this hose and give it a squeeze. If the idle changes, the hose has a split, probably on the bottom side where you can’t see it. You may be able to temporarily fix it with silicon sealer, but be sure the selaer is DRY before starting the engine again. It’s a common enough BMW issue that the hose is available from good foreign parts suppliers.