1998 Grand Am -- Engine Speed

I replaced the power brake booster, never did one before. In order to give myself another 1/4" to get the master cylinder out of the way, I had to remove the air cleaner and hose. And of course, disconnect connectors to sensors, etc.

Everything appears to be back right! BUT: when I start the engine, it starts around 1200 RPM, then sets a rhythm for itself and drops to 500, up to 1600, back down to 500, up to 1600 ... again, it does it in a rhythm, syncopated if you will.

Oh, plus the brakes are 100% out. But I think (hope!) that's just low brake fluid, master C was almost empty and I may not have refilled it completely; the little black holes are still showing.

That engine speed thing's bugging the heck out of me though. ANY help I could get would be ... well, helpful.

Thanks!
Chris

UPDATE: I found a hard plastic vacuum line to the air cleaner that was disconnected from the back of the engine. I reconnected that, it seemed to take care of the revving problem. The Check Engine light is also off.

The engine is still running rough, though.

Brakes are still out even after I topped off the master cylinder. HOWEVER, I discovered that I can also shift out of Park without depressing the brake pedal!

Could those two issues -- shifting out of Park w/o pressing the brake pedal and the brakes not working in gear -- be related?

Chris

It sounds like you dont have much business working on brakes. They must have the air bled out of them to work.

It sounds like you dont have much business working on brakes. They must have the air bled out of them to work.

I'm bright enough to know that much. I've worked on brakes before, only not to this extent. Nor do I care to in the future.

Meanwhile, it turns out the engine revving issue has returned. Think you might have a useful answer about that?

UPDATE: Worked on this yet again tonight. Turns out the engine revving issue has returned despite having reconnected the vacuum hose. And it's rough as [heck].

All sensors are correctly connected, seated properly, and clean. Nothing was missed.

I don't know why it didn't work before, but the shift lever is now locked again until the brake pedal is depressed. At least that part's normal.

It sounds like you dont have much business working on brakes. They must have the air bled out of them to work.

I apoligize for that remark, I wasn't in a very good mood at the time and didnt mean to attack anyone in any way.

On the master cylinder did you completely remove it. If you did you have to bleed the master cylinder and there is a different way to do that.

Welcome to AF BondoFox !

doctorhrdware is correct, if the MC was replaced you do need to bleed/prime it prior to install. If not thats your brake trouble.

On the reving, you didnt mention the engine, but if its a v6 check the MAF sensor wires. They can get stretched and friad the wires inside the casing and it'll cause your irratic idlle/reving. I'd also double check all the connectors on th eair intake and TB, such as the IAC.

hope that helps.

On the shifter working without pressing the brakes that would indicate the park neutral safty switch wasnt receiving the brake signal so that could have been the plug on the master cyl not making good contact.

Is your power booster brand new or from junk yard? Guys are right about brakes, but for the idling part try to disconnect that big vacuum hose that goes from your buster to your upper plenum plug that vacuum port on the upper plenum with your thumb and have somebody start the engine. If idle becomes normal than you know that your power booster diaphragm is bad.